201. Thromb Res 1999 Nov 1;96(3):229-37
Antithrombotic activities of green tea catechins and (-)-epigallocatechin gallate.
Kang WS, Lim IH, Yuk DY, Chung KH, Park JB, Yoo HS, Yun YP
College of Pharmacy, Chungbuk National University, Cheongju, Korea.
The antithrombotic activities and mode of action of green tea catechins (GTC) and (-)-epigallocatechin gallate (EGCG), a major compound of GTC, were investigated. Effects of GTC and EGCG on the murine pulmonary thrombosis in vivo, human platelet aggregation in vitro, and ex vivo, and coagulation parameters were examined. GTC and EGCG prevented death caused by pulmonary thrombosis in mice in vivo in a dose-dependent manner. They significantly prolonged the mouse tail bleeding time of conscious mice. They inhibited adenosine diphosphate- and collagen-induced rat platelet aggregation ex vivo in a dose-dependent manner. GTC and EGCG inhibited ADP-, collagen-, epinephrine-, and calcium ionophore A23187-induced human platelet aggregation in vitro dose dependently. However, they did not change the coagulation parameters such as activated partial thromboplastin time, prothrombin time, and thrombin time using human citrated plasma. These results suggest that GTC and EGCG have the antithrombotic activities and the modes of antithrombotic action may be due to the antiplatelet activities, but not to anticoagulation activities.
202. J Pharm Pharmacol 1999 Nov;51(11):1325-31 Effects of green tea tannin on cisplatin-induced nephropathy in LLC-PK1 cells and rats. Yokozawa T, Nakagawa T, Lee KI, Cho EJ, Terasawa K, Takeuchi S. Research Institute for Wakan-Yaku, Toyama Medical and Pharmaceutical University, Sugitani, Japan. email@example.com
A study was conducted to clarify whether green tea tannin ameliorated cisplatin-induced renal injury in terms of lactate dehydrogenase and malondialdehyde leakage from a renal epithelial cell line, swine-derived LLC-PK1 cells in culture. Green tea tannin was shown to suppress the cytotoxicity of cisplatin, the suppressive effect increasing with the dose of green tea tannin. The effect of cisplatin was then investigated in rats given green tea tannin for 40 days before cisplatin administration and in control rats given no green tea tannin. In control rats, blood, urinary and renal parameters and the activities of antioxidative enzymes in renal tissue deviated from the normal range, indicating dysfunction of the kidneys. In contrast, rats given green tea tannin showed decreased blood levels of urea nitrogen and creatinine, and decreased urinary levels of protein and glucose, reflecting less damage to the kidney. In this group, the activity of catalase in the renal tissue was increased, while the level of malondialdehyde was decreased, suggesting the involvement of radicals in the normalizing of kidney function. Based on the evidence available it appeared that green tea tannin eliminated oxidative stress and was beneficial to renal function.
203. Biochim Biophys Acta 1999 Oct 18;1472(1-2):42-50
Epigallocatechin gallate and gallocatechin gallate in green tea catechins inhibit extracellular release of Vero toxin from enterohemorrhagic Escherichia coli O157:H7.
Sugita-Konishi Y, Hara-Kudo Y, Amano F, Okubo T, Aoi N, Iwaki M, Kumagai S
Department of Biomedical Food Research, National Institute of Infectious Diseases, Toyama, Tokyo, Japan. firstname.lastname@example.org
We studied the effects of six catechin derivatives (catechin, epigallocatechin, epicatechin, epicatechin gallate, epigallocatechin gallate (EGCg) and gallocatechin gallate (GCg)) in green tea on the production and extracellular release of Vero toxins (VTs) from enterohemorrhagic Escherichia coli (EHEC) cultured at 37 degrees C for 24 h. EGCg and GCg in the culture medium markedly inhibited extracellular VTs release from EHEC cells into the culture supernatant fluid at concentrations of 0.05 mg/ml or higher, as estimated by both the reversed passive latex agglutination assay and cytotoxic assay using Vero cells. Production and extracellular release of maltose binding protein, a periplasmic protein, into the culture supernatant were also inhibited by EGCg and GCg, indicating that their inhibitory effect on release from periplasm into the outer milieu is not specific to VTs, but general to the proteins accumulated in EHEC periplasm.
204. Altern Med Rev 1999 Oct;4(5):360-70
Green tea (Camellia sinensis) extract and its possible role in the prevention of cancer.
Sage Health Clinic, Bend, OR, USA. email@example.com
The American Cancer Society estimates that in the 1980s more than 4. 5 million Americans died of cancer. In addition, there were nearly nine million new cases and about 12 million people were under medical care for cancer. With cancer being the second most common cause of death in the United States population, the possibility that readily-available natural substances may be beneficial in the prevention of cancer warrants closer examination. A growing body of research has demonstrated green tea polyphenols to be powerful antioxidants with anticarcinogenic properties. These polyphenolic compounds, specifically the catechins epigallocatechin-3-gallate (EGCG), epigallocatechin (EGC), and epicatechin-3-gallate (ECG), which account for 30-40 percent of the extractable solids of green tea leaves, are believed to mediate many of the cancer chemopreventive effects. Mechanisms of action may include antioxidant and free-radical scavenging activity, and stimulation of detoxification systems through selective induction or modification of phase I and phase II metabolic enzymes. In addition, green tea may inhibit biochemical markers of tumor initiation and promotion, including the rate of cell replication and thus inhibition of the growth and development of neoplasms. Current studies are hopeful, as they show an inverse association between green tea consumption and cancer risk, supporting a possible chemopreventive effect of green tea. Based on the knowledge that green tea is inexpensive, non-toxic, and is a popular beverage consumed worldwide, clinical trials should be conducted to evaluate the in-vivo effectiveness of green tea polyphenols on the inhibition and chemopreventive treatment of cancer.
205. J Agric Food Chem 1999 Oct;47(10):3967-73
Tea catechin supplementation increases antioxidant capacity and prevents phospholipid hydroperoxidation in plasma of humans.
Nakagawa K, Ninomiya M, Okubo T, Aoi N, Juneja LR, Kim M, Yamanaka K, Miyazawa T
Laboratory of Biodynamic Chemistry, Tohoku University Graduate School of Life Science and Agriculture, Sendai 981-8555, Japan.
The effect of green tea catechin supplementation on antioxidant capacity of human plasma was investigated. Eighteen healthy male volunteers who orally ingested green tea extract (254 mg of total catechins/subject) showed 267 pmol of epigallocatechin-3-gallate (EGCg) per milliliter of plasma at 60 min after administration. The plasma phosphatidylcholine hydroperoxide (PCOOH) levels attenuated from 73.7 pmol/mL in the control to 44.6 pmol/mL in catechin-treated subjects, being correlated inversely with the increase in plasma EGCg level. The results suggested that drinking green tea contributes to prevent cardiovascular disease by increasing plasma antioxidant capacity in humans.
206. ood Chem Toxicol 1999 Sep-Oct;37(9-10):985-92
Phenolics: blocking agents for heterocyclic amine-induced carcinogenesis.
Hirose M, Takahashi S, Ogawa K, Futakuchi M, Shirai T
First Department of Pathology, Nagoya City University, Medical School, Nagoya, Japan.
Chemopreventive effects of synthetic and naturally occurring antioxidants on heterocyclic amine (HCA)-induced rat carcinogenesis and mechanisms of inhibition were assessed. In a medium-term liver bioassay, combined treatment with 0.03% 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and synthetic antioxidants such as 1-O-hexyl-2,3,5-trimethylhydroquinone (HTHQ), butylated hydroxyanisole (BHA), butylated hydroxutoluene (BHT), tert-butylhydroquinone (TBHQ) or propyl gallate, each at a dose of 0.25%, inhibited development of preneoplastic glutathione S-transferase placental form (GST-P) positive foci as compared with MeIQx alone, after initiation with diethylnitrosamine (DEN). Of these antioxidants, HTHQ showed the greatest activity. 8-Hydroxydeoxyguanosine (8-OHdG), a marker for DNA damage induced by active oxygen species, and malonedialdehyde and 4-hydroxynonenal levels were not largely influenced by the treatment with MeIQx or antioxidants, either alone or in combination. In the same medium-term liver bioassay, effects of some naturally occurring antioxidants, such as green tea catechins (GTC), hesperidin, chlorogenic acid, quercetin, rutin, curcumin, daidzin, ferulic acid and genistein were also examined. Of these antioxidants, only GTC tended to inhibit GST-P positive foci development, while quercetin, rutin, curcumin, daidzin, ferulic acid and genistein all exerted significant enhancing effects. Examination of HTHQ influence in a medium term liver bioassay with HCA Glu-P-1, in which the experimental period was extended for up to 26 weeks, also demonstrated a significant decrease in the incidence of liver tumours to 40% in the group treated with 0.5% HTHQ and 0.03% 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1) as compared with the Glu-P-1 alone value of 89%. Effects of HTHQ on colon carcinogenesis induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were evaluated in a two-stage colon carcinogenesis model using 1,2-dimethylhydrazine (DMH) as an initiator. At week 36, the multiplicity of colon tumours induced by 0.02% PhIP after DMH initiation (9.1+/-6.2/rat) was dose-dependently decreased by the combined treatment with 0.5% HTHQ (3.6+/-1.8, P < 0.001) and 0.125% HTHQ (6.2+/-3.2, not significant). Similarly, the incidence of mammary carcinomas in female F344 rats induced by oral administration of 0.02% PhIP (40%) for 52 weeks was significantly decreased by simultaneous treatment with 0.5% HTHQ (5%). Alpha-tocopherol and chlorophyllin only reduced the multiplicity of carcinomas. Analysis of the influence of HTHQ on metabolic activation of Glu-P-1 or PhIP after incubation with rat S9 mixture and NADPH by HPLC, revealed that each major metabolite was strongly reduced by the addition of HTHQ. Immunohistochemically detected PhIP-DNA adduct positive nuclei in the colon induced by continuous oral treatment with 0.02% PhIP for 2 weeks decreased by the combined treatment with 0.5 or 0.125% HTHQ. These results indicate that synthetic antioxidant HTHQ is a very strong chemopreventor of heterocyclic amine (HCA)-induced carcinogenesis and that depressed metabolic activation rather than antioxidant activity is responsible for the observed effect.
207. Toxicol Lett 1999 Sep 20;109(1-2):69-76 Proliferation of hepatic peroxisomes in rats following the intake of green or black tea. Bu-Abbas A, Dobrota M, Copeland E, Clifford MN, Walker R, Ioannides C. School of Biological Sciences, University of Surrey, Guildford, UK.
Rats maintained on green, black or decaffeinated black tea (2.5%, w/v) as their sole drinking fluid displayed higher hepatic CN- insensitive palmitoyl CoA oxidase activity than controls; the extent of increase was similar with the three types of tea. Morphological examination of the liver using electron microscopy revealed an increase in the number of peroxisomes in the tea-treated animals. The same treatment of the animals with green and black tea resulted in a similar rise in hepatic microsomal lauric acid hydroxylation. Analysis by HPLC of the aqueous tea extracts employed in the current study showed that the total flavanol content of the green variety was much higher than the black varieties, and confirmed the absence of caffeine in the decaffeinated black tea. It may be concluded from the present studies that neither caffeine nor flavanoids are likely to be responsible for the proliferation of peroxisomes observed in rats treated with tea.
208. Cancer Res 1999 Sep 15;59(18):4610-7
Inhibition of activator protein 1 activity and cell growth by purified green tea and black tea polyphenols in H-ras-transformed cells: structure-activity relationship and mechanisms involved.
Chung JY, Huang C, Meng X, Dong Z, Yang CS
Laboratory for Cancer Research, College of Pharmacy, Rutgers, The State University of New Jersey, Piscataway 08854, USA.
ras gene mutation, which perpetually turns on the growth signal transduction pathway, occurs frequently in many cancer types. The mouse epidermal JB6 cell line has been transfected with a mutant H-ras gene to mimic carcinogenesis in vitro. These transformed cells (30.7b Ras 12) are able to grow in soft agar, exhibiting anchorage independence and high endogenous activator protein 1 (AP-1) activity, which can be detected by a stable AP-1 luciferase reporter. The present study investigated the ability of different pure green and black tea polyphenols to inhibit this ras signaling pathway. The major green tea polyphenols (catechins), (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin, (-)-epicatechin-3-gallate, (-)-epicatechin, and their epimers, and black tea polyphenols, theaflavin, theaflavin-3-gallate, theaflavin-3'-gallate, and theaflavin-3,3'-digallate (TFdiG), were compared with respect to their ability to inhibit the growth of 30.7b Ras 12 cells and AP-1 activity. All of the tea polyphenols except (-)-epicatechin showed strong inhibition of cell growth and AP-1 activity. Among the catechins, both the galloyl structure on the B ring and the gallate moiety contributed to the growth inhibition and AP-1 activity; the galloyl structure appeared to have a stronger effect on the inhibitory action than the gallate moiety. The epimers of the catechins showed similar inhibitory effects on AP-1 activity. The addition of catalase to the incubation of the cells with EGCG or TFdiG did not prevent the inhibitory effect on AP-1 activity, suggesting that H2O2 does not play a significant role in the inhibition by tea polyphenols. Both EGCG and TFdiG inhibited the phosphorylation of p44/42 (extracellular signal-regulated kinase 1 and 2) and c-jun without affecting the levels of phosphorylated-c-jun-NH2-terminal kinase. TFdiG inhibited the phosphorylation of p38, but EGCG did not. EGCG lowered the level of c-jun, whereas TFdiG decreased the level of fra-1. These results suggest that tea polyphenols inhibited AP-1 activity and the mitogen-activated protein kinase pathway, which contributed to the growth inhibition; however, different mechanisms may be involved in the inhibition by catechins and theaflavins.
209. Cancer Lett 1999 Sep 1;143(2):179-83
Chemoprevention studies of heterocyclic amine-induced colon carcinogenesis.
Xu M, Dashwood RH
The Linus Pauling Institute, and Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis 97331-6512, USA.
The cooking of meat and fish produces heterocyclic amine mutagens, including 2-amino-1-methyl-6-phenylimidazo[4,5b]pyridine (PhIP) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). Chronic administration of PhIP or IQ to the F344 rat induces tumors at several sites, including adenocarcinomas of the colon, and short-term treatment leads to the formation of colonic aberrant crypt foci (ACF). We have used these end-points to identify potential chemopreventive agents that might be effective against heterocyclic amine colon carcinogens. Typically, IQ or PhIP were administered to groups of 10-15 rats by oral gavage on alternating days in weeks 3 and 4, and ACF were scored after 8, 12, or 16 weeks or tumors were detected at 52 weeks. To distinguish between 'blocking' and 'suppressing' agents, potential inhibitors were administered during the initiation or post-initiation phases, respectively, and subsequent studies focused on the inhibitory mechanisms. Among the most effective inhibitors identified to date, and their major mechanisms, were the following: chlorophyllin (molecular complex formation); indole-3-carbinol (inhibition and induction of cytochromes P450 and phase II enzymes); green and black tea catechins (induction of UDP-glucuronosyl transferase, inhibition of NADPH-cytochrome P450 reductase, scavenging of reactive intermediates); and conjugated linoleic acids (inhibition of cytochrome P450 and prostaglandin H synthase).
210. Pharmacology 1999 Jul;59(1):34-44
Effects of green tea catechins on membrane fluidity.
Department of Dental Pharmacology, Asahi University School of Dentistry, Hozumi, Gifu, Japan. firstname.lastname@example.org
Catechins originating from green tea have been used in plaque inhibition for caries prevention and treatment for liver damage because of their antibacterial activity against cariogenic bacteria and protective activity on hepatic cells. The effects of catechins on membrane fluidity were studied by a fluorescence polarization method using liposomes prepared with dipalmitoylphosphatidylcholine and dioleoylphosphatidylcholine to assess their pharmacological mechanism at micromol/l levels found in human body fluids after clinical application. All eight catechins tested, ranging from 1 to 1,000 micromol/l, significantly reduced membrane fluidity in both hydrophilic and hydrophobic regions of lipid bilayers. catechin gallate esters were superior in fluidity reduction to the corresponding nonesters. The fluidity-reducing degree was different between the cis and trans forms, suggesting the stereospecific activity of catechins. A reference antiplaque agent, chlorhexidine, similarly reduced membrane fluidity at the antibacterial concentration. (+)-Catechin (250 micromol/l) and (-)-epigallocatechin gallate (2.5 micromol/l) significantly prevented the membrane fluidization induced by hepatotoxic chloroform. These results indicate that the reduction in membrane fluidity is responsible for the antiplaque and hepatoprotective effects of green tea catechins.
211. Eur J Nutr 1999 Jun;38(3):149-57
Green tea extract decreases plasma malondialdehyde concentration but does not affect other indicators of oxidative stress, nitric oxide production, or hemostatic factors during a high-linoleic acid diet in healthy females.
Freese R, Basu S, Hietanen E, Nair J, Nakachi K, Bartsch H, Mutanen M
Division of Nutrition, University of Helsinki, Finland. email@example.com
BACKGROUND: green tea contains polyphenolic catechins which can act as antioxidants and thus decrease the risk for cardiovascular diseases. AIM OF THE STUDY: To investigate whether green tea extract differs from placebo in its effects on markers of antioxidant status, lipid peroxidation, nitric oxide production, thromboxane production, and blood coagulation during a controlled high linoleic acid diet in healthy subjects. METHODS: Twenty healthy non-smoking females (23-50 years) participated in a 4-week controlled intervention study. The experimental diet was rich in linoleic acid (9 en%) and contained fat, protein, and carbohydrates: 27, 14, and 59 en%, respectively. In addition, the subjects ingested encapsulated green tea extract (3 g/d) or placebo mixture in a double-blind manner. Fasting blood samples and five 24-hour urines were collected before and at the end of the 4-week experimental period. Same samples were received from 10 control subjects. RESULTS: green tea extract significantly decreased plasma malondialdehyde (MDA) concentration in comparison with the placebo treatment. The treatments did not differ in serum lipids, indicators of antioxidant status, urinary 8-isoprostaglandin F2 alpha, 2,3-dinorthromboxane B2, nitric oxide metabolites or coagulation indicators. CONCLUSIONS: We conclude that an amount of green tea extract which corresponds to 10 cups of tea per day for 4 weeks does not have specific effects on several indicators related to risk of cardiovascular diseases in comparison with placebo treatment. The relatively small but significant decrease in lipid peroxidation indicated by decreased plasma MDA was not associated with changes in markers of oxidative stress (urinary 8-isoprostaglandin F2 alpha and blood oxidized glutathione) or hemostasis.
212, J Agric Food Chem 1999 May;47(5):2020-5
Regeneration of alpha-tocopherol in human low-density lipoprotein by green tea catechin.
Zhu QY, Huang Y, Tsang D, Chen ZY
Departments of Biochemistry and Physiology, The Chinese University of Hong Kong, Shatin, Hong Kong.
Oxidative modification of low-density lipoproteins (LDL) may play an important role in the development of atherosclerosis. alpha-Tocopherol functions as a major antioxidant in human LDL. The present study was to test whether green tea catechins (GTC) would protect or regenerate alpha-tocopherol in human LDL. The oxidation of LDL incubated in sodium phosphate buffer (pH 7.4, 10 mM) was initiated by addition of 1.0 mM of 2,2'-azobis(2-amidinopropane) dihydrochloride at 40 degrees C. It was found that alpha-tocopherol was completely depleted within 1 h. Under the same experimental conditions, the longjing GTC extracts demonstrated a dose-dependent protective activity to alpha-tocopherol in LDL at concentrations ranging from 2 to 20 microM. Four pure epicatechin derivatives showed varying protective activity against depletion of alpha-tocopherol in LDL with (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG) being less effective than (-)-epicatechin (EC) and (-)-epicatechin gallate (ECG). The results showed that addition of longjing GTC extracts, EC, ECG, and EGCG at 5, 10, and 15 min to the incubation mixture demonstrated a gradual regeneration of alpha-tocopherol in human LDL.
213. Chem Res Toxicol 1999 Apr;12(4):382-6
Antioxidant chemistry of green tea catechins. Identification of products of the reaction of (-)-epigallocatechin gallate with peroxyl radicals.
Valcic S, Muders A, Jacobsen NE, Liebler DC, Timmermann BN
Department of Pharmacology & Toxicology, College of Pharmacy, The University of Arizona, Tucson, Arizona 85721, USA.
(-)-Epigallocatechin gallate (EGCG), isolated from green tea, displays antioxidant properties and is thought to act as an antioxidant in biological systems. However, the specific mechanisms of its antioxidant actions remain unclear. In this study, we have isolated and identified for the first time two reaction products of EGCG derived from its reaction with peroxyl radicals generated by thermolysis of the initiator 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN). The products include a seven-membered B-ring anhydride and a novel dimer. The identification of these products provides the first unambiguous proof that the principal site of antioxidant reactions on the EGCG molecule is the trihydroxyphenyl B ring, rather than the 3-galloyl moiety. In contrast to phenoxyl radicals from simple phenolic antioxidants, an initially formed EGCG phenoxyl radical apparently does not form stable addition products with AMVN-derived peroxyl radicals. Characteristic reaction products may provide novel markers for EGCG antioxidant reactions in living systems.
214. Proc Soc Exp Biol Med 1999 Apr;220(4):239-43
Cancer chemopreventive mechanisms of tea against heterocyclic amine mutagens from cooked meat.
Dashwood RH, Xu M, Hernaez JF, Hasaniya N, Youn K, Razzuk A
The Linus Pauling Institute, and Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, Oregon 97331-6512, USA.Rod.Dashwood@orst.edu
Cooking meat and fish under normal conditions produces heterocyclic amine mutagens, several of which have been shown to induce colon tumors in experimental animals. In our search for natural dietary components that might protect against these mutagens, it was found that green tea and black tea inhibit the formation of heterocyclic amine-induced colonic aberrant crypt foci (ACF) in the rat. Since ACF are considered to be putative preneoplastic lesions, we examined the inhibitory mechanisms of tea against the heterocyclic amines. In the initial studies using the Salmonella mutagenicity assay, green tea and black tea inhibited according to the concentration of tea leaves during brewing and the time of brewing; a 2-3-min brew of 5% green tea (w/v) was sufficient for >90% antimutagenic activity. N-hydroxylated heterocyclic amines, which are direct-acting mutagens in Salmonella, were inhibited by complete tea beverage and by individual components of tea, such as epigallocatechin-3-gallate (EGCG). Inhibition did not involve enhanced mutagen degradation, and EGCG and other catechins complexed only weakly with the mutagens, suggesting electrophile scavenging as an alternative mechanism. Enzymes that contribute to the metabolic activation of heterocyclic amines, namely microsomal NADPH-cytochrome P450 reductase and N, O-acetyltransferase, were inhibited by tea in vitro. Studies in vivo established that tea also induces cytochromes P450 and Phase II enzymes in a manner consistent with the rapid metabolism and excretion of heterocyclic amines. Collectively, the results indicate that tea possesses anticarcinogenic activity in the colon, and this most likely involves multiple inhibitory mechanisms.
215. Proc Soc Exp Biol Med 1999 Apr;220(4):203-9
Plasma and lipoprotein levels of tea catechins following repeated tea consumption.
van het Hof KH, Wiseman SA, Yang CS, Tijburg LB
Unilever Research Vlaardingen, 3130 AC Vlaardingen, The Netherlands. firstname.lastname@example.org
Epidemiological studies suggest that antioxidant flavonoids in tea may reduce the risk of cardiovascular disease, possibly via protection of low-density lipoproteins (LDL) against oxidation. However, the extent of absorption of tea flavonoids and their accumulation in LDL during regular consumption of tea is not clear. Therefore we investigated plasma and lipoprotein levels of catechins during tea consumption and the impact on LDL oxidizability ex vivo. Eighteen healthy adults consumed, in an incomplete balanced cross-over design, green tea, black tea, black tea with milk or water, one cup every 2 hr (eight cups/day) for three days. Blood samples were obtained in the mornings and evenings of each day. Plasma total catechin concentration was determined in all blood samples, and the distribution of catechins among lipoproteins was determined at the end of the third day (t = 60 hr). The resistance of LDL to copper-induced oxidation ex vivo was assessed before tea consumption and at t = 60 hr. Repeated tea consumption during the day rapidly increased plasma total catechin levels whereas they declined overnight when no tea was consumed. There was a gradual increase in plasma levels in the mornings (respectively, 0.08 microM vs. 0.20 microM on first and last day of black tea consumption) and evenings (respectively, 0.29 microM vs. 0.34 microM on first and last day of black tea consumption). green tea catechins were mainly found in the protein-rich fraction of plasma (60%) and in high-density lipoproteins (23%). Although present in LDL, the concentration of catechins in LDL was not sufficient to enhance the resistance of LDL to oxidation ex vivo. Addition of milk to black tea did not affect any of the parameters measured. In conclusion, the present study shows that catechin levels in blood rapidly increase upon repeated tea consumption. The accumulation of catechins in LDL particles is not sufficient to improve the intrinsic resistance of LDL to oxidation ex vivo.
216. Cancer Lett 1999 Feb 8;136(1):79-82
Effect of polyphenon-60 on the development of renal cell tumors in rats treated with N-ethyl-N hydroxyethylnitrosamine.
Yoshioka N, Hiasa Y, Cho M, Kitahori Y, Hirao K, Konishi N, Kuwashima S
Department of Pathology, Nara Medical University, Kashihara, Japan.
Green tea consumed as a beverage in Asia contains polyphenols, which contain about a 15% mixture of catechins. The present paper reports the effect of polyphenon-60 (60% pure catechin) on the development of renal cell neoplasms in Wistar rats pretreated with N-ethyl-N-hydroxyethylnitrosamine (EHEN): 0.1% polyphenon-60 in block diet was given over a period of 30 weeks while EHEN was given in drinking water for 2 weeks. The results appears to show a tendency for green tea catechins (GTC) to decrease the incidence of renal cell tumors greater than 3 mm in diameter in Wistar rats but not tumors that are less than 3 mm in diameter. Polyphenon-60 did not affect EHEN initiation in the kidneys of rats. It is postulated that free radicals induced by EHEN may be suppressed by GTC, resulting in a lowering of the tendency for tumor growth.
217. Cancer Epidemiol Biomarkers Prev 1999 Jan;8(1):83-9
Human salivary tea catechin levels and catechin esterase activities: implication in human cancer prevention studies.
Yang CS, Lee MJ, Chen L
College of Pharmacy, Rutgers, The State University of New Jersey, Piscataway 08854-8020, USA.
Because of the possible application of tea in the prevention of oral and esophageal cancers, the salivary levels of tea catechins were determined in six human volunteers after drinking tea. Saliva samples were collected after thoroughly rinsing the mouth with water. After drinking green tea preparations equivalent to two to three cups of tea, peak saliva levels of (-)-epigallocatechin (EGC; 11.7-43.9 microg/ml), EGC-3-gallate (EGCG; 4.8-22 microg/ml), and (-)-epicatechin (EC; 1.8-7.5 microg/ml) were observed after a few minutes. These levels were 2 orders of magnitude higher than those in the plasma. The elimination half-life (t(1/2)) of the salivary catechins was 10-20 min, much shorter than that of the plasma. Holding a tea solution in the mouth for a few minutes without swallowing produced even higher salivary catechin levels, but taking tea solids in capsules resulted in no detectable salivary catechin level. Holding an EGCG solution in the mouth resulted in EGCG and EGC in the saliva and, subsequently, EGC in the urine. The results suggest that EGCG was converted to EGC in the oral cavity, and both catechins were absorbed through the oral mucosa. A catechin esterase activity that converts EGCG to EGC was found in the saliva. The enzyme was likely of human origin, but the activity was not inhibited by common human esterase inhibitor. The present results suggest that slowly drinking tea is a very effective way of delivering rather high concentrations of catechins to the oral cavity and then the esophagus.
218. Life Sci 1999;65(21):PL241-6
Inhibition of tyrosinase by green tea components.
No JK, Soung DY, Kim YJ, Shim KH, Jun YS, Rhee SH, Yokozawa T, Chung HY
College of Pharmacy, Research Institute of Drug Development, Pusan National University, Kumjung-Gu, Korea.
The pigment melanin in human skin is a major defense mechanism against ultraviolet light of the sun, but darkened skin color, which is the result of increased and redistributed epidermal melanin, could be a serious aesthetic problem. Epidemiologically, it is well known that the consumption of green tea may help prevent cancers in humans and also reduce several free radicals including peroxynitrite. In the present study, to assess the efficacy of the inhibition of mushroom tyrosinase (monophenol monooxygenase EC 22.214.171.124), ten kinds of Korean traditional teas were screened for their tyrosinase inhibitory activity. green tea was the strongest inhibitor, and the major active constituents in the tea are (-)-epicatechin 3-O-gallate (ECG), (-)-gallocatechin 3-O-gallate (GCG), and (-)-epigallocatechin 3-O-gallate (EGCG). All are catechins with gallic acid group as an active site. The kinetic analysis for inhibition of tyrosinase revealed a competitive nature of GCG with this enzyme for the L-tyrosine binding at the active site of tyrosinase.
219. Carcinogenesis 1998 Dec;19(12):2201-4
(-)-Epigallocatechin-3-gallate inhibition of ultraviolet B-induced AP-1 activity.
Barthelman M, Bair WB, Stickland KK, Chen W, Timmermann BN, Valcic S, Dong Z, Bowden GT
Department of Radiation Oncology, University of Arizona Health Sciences Center, Tucson 85724, USA.
Green tea polyphenols have been shown to inhibit cancer in a variety of tumor models, including ultraviolet B (UVB)-induced non-melanoma skin cancer. In green tea extracts, the major dry mass constituent is the family of catechins, of which (-)-epigallocatechin-(3)-gallate (EGCG) is considered to be important for the chemopreventive activity. EGCG has been shown to have antioxidant properties, but there has been little progress toward identifying the specific targets and mechanisms of its action. Using cultured human keratinocytes, we show that UVB-induced AP-1 activity is inhibited by EGCG in a dose range of 5.45 nM to 54.5 microM. EGCG is effective at inhibiting AP-1 activity when applied before, after or both before and after UVB irradiation. EGCG also inhibits AP-1 activity in the epidermis of a transgenic mouse model. This work begins to define a mechanism by which EGCG could be acting to inhibit UVB-induced tumor formation.
220. Biochem Mol Biol Int 1998 Dec;46(5):895-903
Relationship between rate and extent of catechin absorption and plasma antioxidant status.
Pietta P, Simonetti P, Gardana C, Brusamolino A, Morazzoni P, Bombardelli E
ITBA-CNR, Milan, Italy.
Flavonoids are described to exert a large array of biological activities, which are mostly ascribed to their radical-scavenging, metal chelating and enzyme modulation ability. Most of these evidences have been obtained by in vitro studies on individual compounds and at doses largely exceeding those dietary. Little is known about a possible relationship between rate and extent of the absorption and modifications of plasma antioxidants. To elucidate this aspect, human volunteers were supplemented with single doses of green tea catechins in free (Greenselect) or phospholipid complex form (Greenselect Phytosome) equivalent to 400 mg epigallocatechingallate (EGCg). EGCg was chosen as biomarker for green tea catechin absorption, and its time course plasma concentration was correlated to the subsequent percent variations of plasma ascorbate, total glutathione, alpha-tocopherol, beta-carotene and Total Radical Antioxidant Parameter (TRAP). green tea catechins were absorbed more extensively when administered as phospholipid complex rather than as free catechins. Single dose intake of both forms of catechins produced a transient decrease (10-20%) of plasma ascorbate and total glutathione and an increase of plasma TRAP (16-19%). These variations were consistent with the plasmatic levels of EGCg, ascorbate and total glutathione.
221. Chem Biol Interact 1998 Jul 3;114(1-2):109-19
Inhibition of linoleic acid hydroperoxide-induced toxicity in cultured human umbilical vein endothelial cells by catechins.
Kaneko T, Matsuo M, Baba N
Laboratory of Biochemistry and Isotopes, Tokyo Metropolitan Institute of Gerontology, Japan. email@example.com
The protective effect of catechins, major components of green tea, was studied in cultured human umbilical vein endothelial cells exposed to toxicity induced by linoleic acid hydroperoxide (LOOH). In the case where cells were incubated in medium containing both LOOH and catechins, (+)-catechin (C) was effective in suppressing of LOOH-induced cytotoxicity, but (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epigallocatechin gallate (EGCG) had no effect. EGCG monoglucoside (EGCG-G1) and EGCG diglucoside (EGCG-G2), apophilic derivatives of EGCG, show a protective effect on LOOH-induced cytotoxicity when present at the time of treatment with LOOH. On the other hand, when cells were incubated with catechins for 24 h before treatment with LOOH there was no protection against the oxidative damage by LOOH. Furthermore, the interaction between catechins and alpha-tocopherol was examined under these culture conditions. C showed a synergistic effect with alpha-tocopherol in protecting against LOOH-induced damage. These results suggest that catechins interact with LOOH present in the medium or near the surface of membranes, but not with LOOH incorporated into cellular membranes and that catechins are able to interact with alpha-tocopherol to provide synergistic protection against the cytotoxicity of LOOH.
222. Br J Pharmacol 1998 Jul;124(6):1227-37
Epigallocatechin suppression of proliferation of vascular smooth muscle cells: correlation with c-jun and JNK.
Lu LH, Lee SS, Huang HC
Department of Pharmacology, College of Medicine, National Taiwan University, Taipei.
1. The mechanisms of the antiproliferative effect of epigallocatechin, one of the catechin derivatives found in green tea, in vascular smooth muscle cells were studied. The proliferative response was determined from the uptake of tritiated thymidine. 2. In the concentration range of 10(-6) to 10(-4) M, catechin, epicatechin, epigallocatechin, epicatechin gallate and epigallocatechin, epigallocatechin gallate, concentration-dependently inhibited the proliferative response stimulated by serum in rabbit cultured vascular smooth muscle cells. catechin and epicatechin were less effective in inhibiting the serum-stimulated smooth muscle cell proliferation, indicating that the galloyl group may be important for full inhibitory activity. 3. Epigallocatechin (EGC) inhibited the proliferative responses in different cells including rat aortic smooth muscle cells (A7r5 cells), rabbit cultured aortic smooth muscle cells, human coronary artery smooth muscle cells, and human CEM lymphocytes in a concentration-dependent manner. The possible mechanisms of the antiproliferative effect of EGC were further studied in A7r5 cells. 4. The membranous protein tyrosine kinase activity stimulated by serum in A7r5 cells was significantly reduced by 10(-5) M EGC. In contrast, the cytosolic protein kinase C activity stimulated by phorbol ester was unaffected by directly incubating with EGC (10(-6)-10(-4) M). 5. We also performed Western blot analysis using the anti-phosphotyrosine monoclonal antibody PY20. EGC (10(-5) M) reduced the levels of tyrosine phosphorylated proteins with different molecular weights, indicating that EGC may inhibit the protein tyrosine kinase activity or stimulate the protein phosphatase activity. 6. Reverse transcription-polymerase chain reaction analysis of c-fos, c-jun and c-myc mRNA levels demonstrated that c-jun mRNA level after serum-stimulation was significantly reduced by 10(-5) M EGC. However, the reduction of c-fos and c-myc mRNA levels by 10(-5) M EGC did not achieve significance. 7. Western blot analysis using the antibody against JNK (c-jun N-terminal kinase) and ERK (extracellular signal-regulated kinase) demonstrated that the level of phosphorylated JNK1, but not phosphorylated ERK1 and ERK2, was reduced by 10(-5) M EGC. Direct measurement of kinase activity by immune complex kinase assay confirmed that JNK1 activity was inhibited by EGC treatment. These results demonstrate that EGC preferentially reduced the activation of JNK/SAPK (stress-activated protein kinase) signal transduction pathway. 8. It is suggested that the antiproliferative effect of epigallocatechin on vascular smooth muscle cells may partly be mediated through inhibition of protein tyrosine kinase activity, reducing c-jun mRNA expression and inhibiting JNK1 activation. Tea catechins may be useful as a template for the development of drugs to prevent the pathological changes of atherosclerosis and post-angioplasty restenosis.
223. Mutat Res 1998 Jun 18;402(1-2):299-306
Antimutagenic activity of tea towards 2-hydroxyamino-3-methylimidazo[4,5-f]quinoline: effect of tea concentration and brew time on electrophile scavenging.
Hernaez JF, Xu M, Dashwood RH
Department of Environmental Biochemistry, University of Hawaii, Honolulu, HI 96822, USA.
Green tea and black tea inhibit colon carcinogenesis in rats exposed to the cooked meat-derived mutagen 2-amino-3-methylimidazo[4, 5-f]quinoline (IQ). The present study compared the inhibitory activities of green tea and black tea towards a direct-acting mutagenic metabolite of IQ, namely 2-hydroxyamino-3-methylimidazo[4, 5-f]quinoline (N-hydroxy-IQ), under various brewing conditions. The following observations were made: (a) green tea (Sencha midoriiro) and black tea (English Breakfast tea) brewed at concentrations of 1. 25%, 2.5% or 5.0% (w/v) dose-relatedly inhibited the mutagenic activity of N-hydroxy-IQ in the Salmonella assay, (b) most of the antimutagenic components were released from the teas within 1-2 min of brewing, (c) under identical brewing conditions, green tea was significantly more effective than black tea, and (d) fractionation of green tea by HPLC revealed that most of the antimutagenic activity co-eluted with the compounds epigallocatechin (EGC) and epigallocatechin-3-gallate (EGCG), both of which are known for their anti-oxidant properties. These results suggest that catechins in tea might protect against such diverse reactive intermediates as free radicals and electrophiles formed during the metabolic activation of carcinogens and mutagens.
224. Mutat Res 1998 Jun 18;402(1-2):237-45
Inhibitory effects of antioxidants on formation of heterocyclic amines.
Oguri A, Suda M, Totsuka Y, Sugimura T, Wakabayashi K
Cancer Prevention Division, National Cancer Center Research Institute, 1-1 Tsukiji 5-chome, Chuo-ku, Tokyo 104, Japan.
It is important to search for effective antioxidants to suppress formation of mutagenic and carcinogenic heterocyclic amines (HCAs), like 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), because these HCAs are considered to be probable human carcinogens. The effects of various food-derived antioxidants on MeIQx formation were examined by their addition (0.2 mmol each) to mixtures of creatine (0.4 mmol), glycine (0.4 mmol) and glucose (0.2 mmol), and heating at 128 degreesC for 2 h. Glycine was replaced by l-phenylalanine in the case of PhIP formation. Among the 14 kinds of antioxidants tested, green tea catechins and the major component [(-)-epigallocatechin gallate], two flavonoids (luteolin and quercetin) and caffeic acid were found to clearly suppress the formation of both MeIQx and PhIP, being 3.2-75% of the level of the controls. These phenolic antioxidants also reduced the total mutagenicity of the heated mixtures. The results suggest that foodstuffs containing catechins, flavonoids and caffeic acid may suppress the formation of HCAs in cooked foods.
225. Carcinogenesis 1998 Apr;19(4):611-6
Inhibition of growth and induction of apoptosis in human cancer cell lines by tea polyphenols.
Yang GY, Liao J, Kim K, Yurkow EJ, Yang CS
Laboratory for Cancer Research, College of Pharmacy, Rutgers University, Piscataway, NJ 08855-0789, USA.
In order to study the biological activities of tea preparations and purified tea polyphenols, their growth inhibitory effects were investigated using four human cancer cell lines. Growth inhibition was measured by [3H]thymidine incorporation after 48 h of treatment. The green tea catechins (-)-epigallocatechin-3-gallate (EGCG) and (-)-epigallocatechin (EGC) displayed strong growth inhibitory effects against lung tumor cell lines H661 and H1299, with estimated IC50 values of 22 microM, but were less effective against lung cancer cell line H441 and colon cancer cell line HT-29 with IC50 values 2- to 3-fold higher. (-)-Epicatechin-3-gallate, had lower activities, and (-)-epicatechin was even less effective. Preparations of green tea polyphenols and theaflavins had higher activities than extracts of green tea and decaffeinated green tea. The results suggest that the growth inhibitory activity of tea extracts is caused by the activities of different tea polyphenols. Exposure of H661 cells to 30 microM EGCG, EGC or theaflavins for 24 h led to the induction of apoptosis as determined by an annexin V apoptosis assay, showing apoptosis indices of 23, 26 and 8%, respectively; with 100 microM of these compounds, the apoptosis indices were 82, 76 and 78%, respectively. Incubation of H661 cells with EGCG also induced a dose-dependent formation of H2O2. Addition of H2O2 to H661 cells caused apoptosis in a manner similar to that caused by EGCG. The EGCG-induced apoptosis in H661 cells was completely inhibited by exogenously added catalase (50 units/ml). These results suggest that tea polyphenol-induced production of H2O2 may mediate apoptosis and that this may contribute to the growth inhibitory activities of tea polyphenols in vitro.
226. Oncol Rep 1998 Mar-Apr;5(2):527-9
Induction of apoptosis in human stomach cancer cells by green tea catechins.
Hibasami H, Komiya T, Achiwa Y, Ohnishi K, Kojima T, Nakanishi K, Akashi K, Hara Y
Faculty of Medicine, Mie University, Tsu-city, Mie 514, Japan.
The exposure of human stomach cancer KATO III cells to green tea catechin extract and epigallocatechin gallate (EGCG), a main component of the extract led to both growth inhibition and the induction of programmed cell death (apoptosis). Morphological changes showing apoptotic body were observed in the cells treated with green tea catechin extract and EGCG. The fragmentation of DNA to oligonucleosomal-sized fragments, characteristic of apoptosis was determined to be concentration- and time-dependent. These data suggest that drinking of green tea in large amounts is recommended possibly to protect humans from stomach cancer.
227. Biosci Biotechnol Biochem 1998 Mar;62(3):532-4
Isolation and identification of acetyl-CoA carboxylase inhibitors from green tea (Camellia sinensis).
Watanabe J, Kawabata J, Niki R
Department of Bioscience and Chemistry, Faculty of Agriculture, Hokkaido University, Sapporo, Japan. firstname.lastname@example.org
An aqueous methanol extract from green tea showed potent acetyl-CoA carboxylase inhibitory activity. An active compound was isolated from the extract and identified as (-)-epigallocatechin gallate by instrumental analyses. The IC50 value of (-)-epigallocatechin gallate was 3.1 x 10(-4) M. Among tea catechins and related compounds, nearly equal activity was found in (-)-epigallocatechin gallate and (-)-epicatechin gallate, whereas (+)-catechin, (-)-epicatechin, (-)-epigallocatechin, gallic acid and methyl gallate each had no inhibitory activity. These results indicate that the 3-O-gallate group of the catechin structure was necessary for this activity. (-)-Epigallocatechin gallate inhibited triglyceride accumulation in 3T3-L1 cells at a concentration of 1.0 x 10(-7) M or higher.
228. Eur J Cancer Prev 1998 Feb;7(1):61-7
Prevention by antioxidants of heterocyclic amine-induced carcinogenesis in a rat medium-term liver bioassay: results of extended and combination treatment experiments.
Hirose M, Futakuchi M, Tanaka H, Orita SI, Ito T, Miki T, Shirai T
First Department of Pathology, Nagoya City University, Medical School, Japan.
The effects of 1-O-hexyl-2,3,5-trimethylhydroquinone (HTHQ) and other antioxidants on heterocyclic amine (HCA)-induced rat hepatocarcinogenesis were examined in a medium-term liver bioassay. In one study the experimental period was extended for up to 28 weeks to confirm the inhibition of 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1)-induction of glutathione-S-transferase placental form (GST-P) positive foci detected earlier in an 8-week experiment. Six-week-old male F344 rats were given a single i.p. injection of diethylnitrosamine (DEN) (200 mg/kg b.w.), and starting 2 weeks later, groups of 20 animals received a diet containing 0.03% Glu-P-1 together with 0.5% HTHQ, Glu-P-1 alone, HTHQ alone or a basal diet alone for 26 weeks. Three weeks after the DEN injection, animals were subjected to partial hepatectomy. The combined incidence of hepatocellular adenomas and carcinomas in the group fed Glu-P-1 alone was 89%, in contrast to 40% with simultaneous HTHQ treatment, and near the control level of 30% without Glu-P-1 and HTHQ. In the second experiment, to assess the effects of HTHQ on HCAs in combination, to mimic the human situation, after DEN initiation groups of 15 rats received diets containing a 0.0155% HCA mixture (0.003% Glu-P-1, 0.0015% 3-amino-1,4-dimethyl-5-H-pyrido[4,3-b]indole (Trp-P-1), 0.004% 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeAaC), 0.003% 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 0.004% 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), which are all heptocarcinogens) together with 0.5 or 0.125% HTHQ, HCA alone, 0.5 or 0.125% HTHQ alone, or basal diet alone for 6 weeks. The numbers of GST-P positive foci decreased in a dose-dependent manner to 12.2+/-3.1 and 7.2+/-2.4 by the simultaneous treatment with 0.125 and 0.5% HTHQ, respectively, from a value of 17.6+/-3.6 for the HCA mix alone. In a third experiment, after DEN initiation, groups of 15 rats were placed on diets containing 0.02% MeIQx together with 0.25% HTHQ, 0.05% phenylethyl isothiocyanate (PEITC), 1% green tea catechins (GTC) or a mixture of HTHQ, PEITC and GTC, MeIQx alone, antioxidants alone or in combination, or basal diet alone for 6 weeks. These compounds were previously shown to inhibit HCA-associated GST-P positive foci. The numbers of GST-P positive foci in rats treated with MeIQx together with HTHQ (7.7+/-2.6) or antioxidant mixture (0.4+/-2.8) were significantly lower than with MeIQx alone (12.1+/-3.1), but a clear synergistic effect was not demonstrated. These results confirmed the ability of HTHQ to inhibit hepatocarcinogenesis induced by HCAs.
229. Mutat Res 1998 Jan 13;412(1):91-8
Inhibition of N-nitrosation of secondary amines in vitro by tea extracts and catechins.
Tanaka K, Hayatsu T, Negishi T, Hayatsu H
Meiji College of Pharmacy, Tokyo, Japan.
Inhibition of nitrite-mediated N-nitrosation of dimethylamine, morpholine and N-methylaniline by tea extracts and by 6 individual catechins in the extracts was studied. The inhibitions were detected by quantifying the nitrosamines formed. Eight different kinds of teas (5 green teas, a roasted green tea, an oolong tea, and a black tea) were examined for their inhibitory abilities and for their catechin contents, with an attempt to correlate the inhibitory activities to the catechin contents. The results showed that (1) the green tea extracts inhibit strongly the N-nitrosation of the three secondary amines tested, (2) the 6 catechins, notably epigallocatechin, are capable of blocking the N-nitrosations very efficiently, even more efficiently than ascorbic acid, and (3) the inhibition activities of green tea extracts are mostly ascribable to the catechins present in the extracts. These inhibitions occur by rapid reactions between nitrite and the catechins. It was observed that no mutagenicity results from the reaction between the tea extracts and nitrite.
230. Biochem Pharmacol 1997 Dec 15;54(12):1281-6
Inhibition of inducible nitric oxide synthase gene expression and enzyme activity by epigallocatechin gallate, a natural product from green tea.
Chan MM, Fong D, Ho CT, Huang HI
Department of Biomedical Sciences, Pennsylvania College of Podiatric Medicine, Philadelphia 19107-2496, USA. email@example.com
Chronic inflammation has been implicated as the underlying factor in the pathogenesis of many disorders. In the past decade, inflammation-related endogenous production of reactive nitrogen species, similar to oxygen free radicals, has also been suggested as a risk factor for cancer, in addition to the well-studied exogenous nitroso compounds. Epidemiological, in vitro, and animal model studies have implicated green tea to be protective against nitroso compound-induced and inflammation-related cancer. Therefore, we investigated the effect of epigallocatechin-3-gallate (EGCG), one of the known biologically active catechins contained in green tea, on the production of nitric oxide (NO.). We have shown previously that EGCG reduces NO. production as measured by nitrite accumulation in the culture medium. Expanding on this finding, in this report we show that EGCG may do so by two mechanisms: reduction of inducible nitric oxide synthase (iNOS) gene expression and inhibition of enzyme activity. Addition of 1-10 microM EGCG to lipopolysaccharide- and interferon-gamma-activated mouse peritoneal cells reduced iNOS mRNA expression concentration dependently, to 82-14%, as measured by relative reverse transcription-polymerase chain reaction. Addition of 50-750 microM EGCG, in a concentration-dependent manner, inhibited the enzyme activity of iNOS, to 85-14%, and neuronal nitric oxide synthase (nNOS), to 93-56%, as measured by citrulline formation. EGCG competitively inhibited binding of arginine and tetrahydrobiopterin, and the gallate structure is important for this action.
231. Biosci Biotechnol Biochem 1997 Dec;61(12):1981-5
Dose-dependent incorporation of tea catechins, (-)-epigallocatechin-3-gallate and (-)-epigallocatechin, into human plasma.
Nakagawa K, Okuda S, Miyazawa T
Food Chemistry Laboratory, Faculty of Agriculture, Tohoku University, Sendai, Japan.
Tea catechins, (-)-epigallocatechin-3-gallate (EGCg) and (-)-epigallocatechin (EGC), have been reported to suppress oxidation of plasma low density lipoprotein (LDL) in vitro. If dietary catechins can be efficiently incorporated into human blood plasma, anti-atherosclerotic effects in preventing oxidative modification of LDL would be expected. In this study, a newly developed chemiluminescence detection-high pressure liquid chromatography (CL-HPLC) method for measuring plasma catechins was used and the incorporation of EGCg and EGC into human plasma was investigated. Healthy subjects orally ingested 3, 5, or 7 capsules of green tea extract (corresponding to 225, 375, and 525 mg EGCg and 7.5, 12.5, and 17.5 mg EGC, respectively). The plasma EGCg and EGC concentrations before the administration were all below the detection limit (< 2 pmol/ml), but 90 min after, significantly and dose-dependently increased to 657, 4300, and 4410 pmol EGCg/ml, and 35, 144, and 255 pmol EGC/ml, in the subjects who received 3, 5, and 7 capsules, respectively. Both EGCg and EGC levels detected in plasma corresponded to 0.2-2.0% of the ingested amount. Catechin intake had no effect on the basal level of endogenous antioxidants (alpha-tocopherol, beta-carotene, and lycopene) or of lipids in plasma. These results suggested that drinking green tea daily would contribute to maintain plasma catechin levels sufficient to exert antioxidant activity against oxidative modification of lipoproteins in blood circulation systems.
232. Biochem Pharmacol 1997 Nov 1;54(9):973-8
Protective effects of tea polyphenols against oxidative damage to red blood cells.
Grinberg LN, Newmark H, Kitrossky N, Rahamim E, Chevion M, Rachmilewitz EA
Department of Hematology, Hadassah University Hospital-Hebrew University Medical School, Jerusalem, Israel.
Tea polyphenols (TPP) from black and green teas were evaluated for their antioxidant effects on normal red blood cells (RBC) and beta-thalassemic RBC membranes challenged with exogenous oxidants in vitro. The TPP of both types protected RBC against primaquine-induced lysis; they also protected the whole cells and the membranes against H2O2-induced lipid peroxidation so that about 80% protection was reached at [TPP] = 10 microg/mL. TPP from black tea at the same concentration protected normal RBC from morphological alterations caused by the peroxide treatment. The mechanism of the effects of TPP was investigated using a chemical system generating .OH (iron + ascorbic acid). TPP from both black and green teas inhibited the .OH fluxes in a concentration-dependent manner, indicating the possibility of iron chelation by TPP. Spectrophotometric titration revealed that TPP could stoichiometrically bind ferric iron to form a redox-inactive Fe-TPP complex. Quantitative analysis suggests that one or more major catechins from the TPP preparations are the likely iron-binding compounds accounting for the antioxidant effects of TPP on RBC.
233. Biosci Biotechnol Biochem 1997 Sep;61(9):1504-6
Inhibition of collagenases from mouse lung carcinoma cells by green tea catechins and black tea theaflavins.
Sazuka M, Imazawa H, Shoji Y, Mita T, Hara Y, Isemura M
School of Food and Nutritional Sciences, University of Shizuoka, Japan.
Theaflavin and theaflavin digallate, which are components of black tea were examined by in vitro invasion assay with mouse Lewis lung carcinoma LL2-Lu3 cells, which are highly metastatic. The compounds inhibited invasion by the tumor cells. Gelatin zymography showed that the cells secreted matrix metalloproteinases (MMPs), probably including MMP-2 and MMP-9, which may be involved in tumor cell invasion and metastasis. Theaflavin and theaflavin digallate also inhibited MMPs from the culture medium of these tumor cells, as did (-)-epigallocatechin gallate. These results suggest that theaflavin, theaflavin digallate, and (-)-epigallocatechin gallate inhibit tumor cell invasion by inhibiting type IV collagenases of the LL2-Lu3 cells.
234. Pancreas 1997 Aug;15(2):109-12
Effect of green tea catechins on the amount of 8-hydroxydeoxyguanosine (8-OHdG) in pancreatic and hepatic DNA after a single administration of N-nitrosobis(2-oxopropyl)amine (BOP).
Takabayashi F, Harada N, Tahara S, Kaneko T, Hara Y
Hamamatsu College, University of Shizuoka, Japan.
Effects of green tea catechins on N-nitrosobis(2-oxopropyl)amine (BOP)-induced oxidative stress in pancreas and liver were examined. Hamsters were divided into two groups: one group was given free access to a 0.1% solution of green tea catechins as drinking water (c-ham) and the other to plain tap water (w-ham) for 1 week before subcutaneous injection of BOP 20 mg/kg body weight. Zero, 1, 2, 6, 12, 24, and 48 h after BOP injection, the pancreas and liver were excised and the tissue concentration of lipid peroxides (TBA values) and the amount of 8-hydroxydeoxyguanosine (8-OHdG) in nuclear DNA were measured. The concentration of lipid peroxides and the amount of 8-OHdG in the pancreas showed similar patterns of change between c- and w-ham. Soon after BOP injection, the concentration of lipid peroxides and the amount of 8-OHdG increased with a peak at 1 and 6 h, respectively. Their peak values of c-ham were significantly depressed compared with those of w-ham. Both levels returned to steady-state levels by 24 h. In the liver, the concentration of lipid peroxides and the amount of 8-OHdG were not affected by BOP administration. These results suggest that BOP induces oxidative damages in the target organ and oral intake of green tea catechins has a protective effect on the oxidative stress.
235. Yakugaku Zasshi 1997 Jul;117(7):448-54
[Effect of tea extracts, catechin and caffeine against type-I allergic reaction].
[Article in Japanese]
Shiozaki T, Sugiyama K, Nakazato K, Takeo T
Institute of Traditional Chinese Medicines, School of Pharmaceutical Sciences, University of Shizuoka, Japan.
The antiallergic effects of green tea, oolong tea, and black tea extracts by hot water were examined. These extracts inhibited the passive cutaneous anaphylaxis (PCA) reaction of rat after oral administration. Three tea catechins, (--)-epigallocatechin (EGC), (--)-epicatechin gallate (ECg), and (--)-epigallocatechin gallate (EGCg) isolated from green tea showed stronger inhibitory effects than that of a green tea extract on the PCA reaction. The inhibitory effects of EGC and EGCg on the PCA reaction were greater than that of ECg. Caffeine also showed a inhibitory effect on the PCA reaction. These results indicate that tea could provide a significant protection against the type-I allergic reaction. These findings also suggest that tea catechins and caffeine play an important role in having an inhibitory effect on the type-I allergic reaction.
236. Cancer Lett 1997 Jun 3;116(1):47-52
Post-initiation inhibitory effects of green tea catechins on 7,12-dimethylbenz[a]anthracene-induced mammary gland carcinogenesis in female Sprague-Dawley rats.
Tanaka H, Hirose M, Kawabe M, Sano M, Takesada Y, Hagiwara A, Shirai T
First Department of Pathology, Nagoya City University Medical School, Mizuho-ku, Japan.
The dose-dependence of green tea catechin (GTC) effects on 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary gland carcinogenesis were investigated in female Sprague-Dawley rats. Groups of 20 6-week-old rats were treated with dietary 1, 0.1 or 0.01% GTC for 2 weeks and then basal diet alone for 35 weeks. At the end of week 1, they received a 25 mg/kg body weight intragastric dose of DMBA. Further groups of 20 7-week-old rats each were given an intragastric dose of 25 mg/kg body weight DMBA, and starting 1 week after DMBA treatment they were placed on diet containing 1, 0.1 or 0.01% GTC or basal diet alone for 35 weeks. Control rats were given 1% GTC or basal diet alone. The final incidences and multiplicities of mammary tumors were not significantly different between the groups treated with GTC at the same time as DMBA, compared to the DMBA alone control group. On the other hand, the final multiplicities of mammary tumors in groups treated with 1% GTC (P < 0.05) or 0.01% GTC (P < 0.01), but not 0.1% GTC, after DMBA treatment were significantly decreased as compared to the control value. These results indicate that whereas GTC may inhibit mammary carcinogenesis in the post-initiation stage, the effect is weak and not dose-dependent.
237. Environ Health Perspect 1997 Jun;105 Suppl 4:971-6
Polyphenols as inhibitors of carcinogenesis.
Yang CS, Lee MJ, Chen L, Yang GY
Laboratory for Cancer Research, Rutgers University, Piscataway, New Jersey 08855-0789, USA. firstname.lastname@example.org
Many polyphenolic compounds have demonstrated anticarcinogenic activities in animal models. These compounds include flavanone, flavonols, isoflavone, and catechins. In this article, tea catechins will be used as an example to illustrate current research in this area. Many laboratory studies have demonstrated the inhibition of tumorigenesis in animal models by different tea preparations. The animal models include tumorigenesis in the mouse lung, rat and mouse esophagi, mouse forestomach, mouse skin, mouse duodenum, rat small intestine, rat and mouse livers, and rat colon. In most of the studies, the inhibitory activity of tea could be demonstrated when tea preparations were given either during or after the carcinogen treatment period. Black tea was also effective, although the activity was weaker than green tea in some experiments. Decaffeinated tea preparations were also active in many model systems. The molecular mechanisms for these broad inhibitory actions are not fully understood. They are most likely related to the biochemical actions of the tea polyphenols, which include antioxidative activities and inhibition of cell proliferation and of tumor promotion-related activities. The effect of tea consumption on human cancers is not clear in spite of numerous investigations. The bioavailability and pharmacokinetics of tea polyphenols are being studied in animals and humans to provide a basis for more quantitative analyses on the effect of tea on carcinogenesis. More mechanistic and dose-response studies will help us to understand the effects of tea consumption on human carcinogenesis.
238. Pancreas 1997 Apr;14(3):276-9
Effects of green tea catechins (Polyphenon 100) on cerulein-induced acute pancreatitis in rats.
Takabayashi F, Harada N
Hamamatsu College, University of Shizuoka, Japan.
Effects of green tea catechins (GTC) on cerulein-induced acute pancreatitis in rats were examined. The acute pancreatitis induced by cerulein (cerulein pancreatitis) was characterized by interstitial edema and vacuolation. When cerulein pancreatitis was induced, prior administration of 0.1% GTC in drinking water for 1 week before the induction significantly decreased the wet weight of the pancreas, the serum level of amylase, and the tissue concentration of lipid peroxides in the pancreas compared with those in nonmedicated rats supplied with plain tap water only. Furthermore, the pancreatic tissue alterations of the medicated rats were milder than those of the nonmedicated rats. These data suggest that GTC have a protective effect on the pathogenesis of cerulein pancreatitis.
239. Cancer Lett 1997 Mar 19;114(1-2):153-8
Screening of anticarcinogenic ingredients in tea polyphenols.
Institute of Nutrition and Food Hygiene, Chinese Academy of Preventive Medicine, Beijing.
A batch of short-term tests were used to test the antimutagenic activities of Chinese green tea water extract (TWE), tea polyphenols (TP), and tea catechins (EGCG, ECG, EGC, EC). In the V79 cell forward gene mutation and V79 cell cytokinesis-block micronuclei tests, all samples showed significant inhibitory effects on mitomycin, which indicates their effects on the initiation stage of chemical carcinogenesis. However, none of the catechins and TP had effects as strong as the TWE on the basis of their relative contents in tea. Of the four catechins, ECG and EGCG were the most potent. Using the V79 cell metabolic co-operation test as an indicator for the promotion stage, TWE and TP showed weak inhibitory effects and the individual catechins showed much stronger inhibition. The test samples also showed non-specific inhibitory effects on HeLa cell growth in soft agar, which was designed to test their effects on the progression stage.
240. Anticancer Drugs 1997 Mar;8(3):265-8
Green tea catechins (EGCG and EGC) have modulating effects on the activity of doxorubicin in drug-resistant cell lines.
Stammler G, Volm M
Deutsches Krebsforschungszentrum, Department 0511, Heidelberg, Germany.
The chemopreventive effect of polyphenols from green tea [e.g. (-)-epigallocatechin gallate (EGCG) and (-)-epigallocatechin (EGC)] against cancer has been demonstrated in several studies. The aim of this investigation was to prove whether these compounds modulate the activity of antineoplastic drugs. Therefore, the influence of EGCG and EGC was tested on doxorubicin-resistant murine sarcoma (S180-dox) and human colon carcinoma (SW620-dox) cell lines. Both substances showed a sensitizing effect on the cell lines if they had been treated with doxorubicin. These results suggest that protein kinase C may be inhibited by EGCG and EGC, and this may lead to a reduced expression of some drug resistance related proteins.
241. Med Hypotheses. 1997 Mar;48(3):215-20.
natural antimutagenic agents may prolong efficacy of human immunodeficiency virus drug therapy.
Nutrition 21, San Diego, CA 92109, USA.
The long-term efficacy of new combination drug therapies for human immunodeficiency virus infection may be limited by the tendency of transfected human immunodeficiency virus to mutate to drug-resistant forms. This argues for the use of safe antimutagenic measures as adjuvants to such therapies. Certain nutrients and food factors-notably selenium, green-tea polyphenols, and cruciferous phytochemicals-can suppress cancer initiation and mutagenesis in animal and cell culture models; epidemiological studies suggest that ambient variations in consumption of these food factors can have an important impact on human cancer rates. Low-fat diets may reduce deoxyribonucleic acid base damage in human leukocytes, whereas increased body iron stores are likely to increase mutation rates. Thus, ample but safe intakes of selenium, green-tea polyphenols, and cruciferous vegetables, in the context of a diet low in fat and assimilable iron, can be expected to prolong the efficacy of drug therapy in subjects infected with the human immunodeficiency virus. These measures can also be recommended for cancer prevention in the general population.
242. Cancer Lett 1997 Jan 30;112(2):141-7
Effects of green tea catechins on the progression or late promotion stage of mammary gland carcinogenesis in female Sprague-Dawley rats pretreated with 7,12-dimethylbenz(a)anthracene.
Hirose M, Mizoguchi Y, Yaono M, Tanaka H, Yamaguchi T, Shirai T
First Department of Pathology, Nagoya City University, Medical School, Japan.
Effects of the green tea catechins (GTCs) on the late promotion or progression stage of mammary gland carcinogenesis were examined in female Sprague-Dawley (SD) rats pretreated with 7,12-dimethylbenz(a)anthracene (DMBA). A total of 84 7-week-old rats received a 50 mg/kg body weight intra-gastric dose of DMBA, and starting 13 weeks thereafter, when the tumor incidence had reached 50%, three groups of 28 animals each were placed on diet containing 0.5% Polyphenon E (58.4% content (-)-epigallocatechin gallate (EGCG)) (groups 1a and 1b), 0.5% EGCG-80 (81% content of EGCG) (groups 2a and 2b) or basal diet alone (groups 3a and 3b) for 23 weeks. The experiment was terminated at week 36. The growth (i.e. change in mean diameter) of mammary tumors present at week 13 (groups 1a, 2a and 3a) was not influenced by the treatment with EGCGs, with no significant intergroup differences in the lesion incidences, multiplicity or size being observed. Values for these parameters did show a tendency for decrease in group 2b (Polyphenon E) as compared to group 3b (control) during the study, but they were not significantly reduced at the sacrifice time point. These results indicate that GTCs are not effective at inhibiting progression of rat mammary carcinogenesis, but Polyphenon E may exert a weak inhibitory effect on the early promotion stage.
243. FEBS Lett 1997 Jan 20;401(2-3):230-4
Green tea catechins such as (-)-epicatechin and (-)-epigallocatechin accelerate Cu2+-induced low density lipoprotein oxidation in propagation phase.
Yamanaka N, Oda O, Nagao S
The Bio-Dynamics Research Institute, Nagoya Memorial Hospital, Tenpaku-ku, Japan.
Effects of (-)-epicatechin (EC) and (-)-epigallocatechin (EGC) on Cu2+-induced low density lipoprotein (LDL) oxidation were studied in initiation and propagation phases. When 1.5 microM EC or EGC was added to the mixture of isolated human LDL and Cu2+ in the initiation phase, the oxidation of LDL was inhibited in agreement with previous findings. In contrast, in the propagation phase, 1.5 microM of EC or EGC worked as an accelerator of the oxidation, and acceleration ratios (maximum about 6 times) were modified depending on the concentrations of catechin used and the oxidation process in the propagation phase. The evidence was obtained from formation of thiobarbituric acid reactive substances (TBARS), detecting conjugated diene measured by absorbance at 234 nm and investigating fragmentation of apoprotein B (apo B) in LDL. Even in the propagation phase of LDL oxidation, the elevated concentrations of EC or EGC worked as inhibitors: after 40 min incubation of LDL with Cu2+, 10.0 microM EC or 2.0 microM EGC inhibited LDL oxidation. Yet, nitric oxide (NO) released from 5 microM zwitterionic polyamine/NO adducts had an inhibitory in all phases of LDL oxidation. These results indicate that catechins such as EC and EGC can act as free radical terminators (reducing agents) or accelerators (oxidizing agents) under oxidation circumstances, which is a different character from NO. From the above evidence, further investigations are needed on many natural flavonoids, the most potent antioxidative compounds in foods.
244. J Cell Biochem Suppl 1997;27:52-8
Influence of tea catechins on the digestive tract.
Food Research Institute, Mitsui Norin Co., Ltd., Shizuoka Pref., Japan.
Tea catechins undergo various metabolic changes after they are taken orally, though a large percentage are excreted intact with the feces. Epidemiological studies suggest a protective effect of tea against various human cancers, including colon and rectum. The bactericidal property of tea catechins plays several roles in the digestive tract. In the small intestine, catechins inhibit alpha-amylase activity, and a certain amount is absorbed into the portal vein. Although catechins are bactericidal, they do not affect lactic acid bacteria. Including tea catechins in the diet for several weeks decreases putrefactive products and increases organic acids by lowering pH. These changes were achieved in tube-fed patients by administering 100 mg of tea catechins (equivalent to a cup of green tea) three times daily with meals for 3 weeks. When catechin administration ceased, the effects reversed after 1 week. catechins should be considered further in colon carcinogenesis studies.
245. Mutat Res 1996 Dec 12;361(2-3):179-86
Bio-antimutagenic activity of green tea catechins in cultured Chinese hamster V79 cells.
Department of Environmental Health Science, Azabu University, Kanagawa, Japan.
The antimutagenic effects of green tea catechins, (-)-epicatechin gallate (ECg) and (-)-epigallocatechin gallate (EGCg) on induction of 6-thioguanine (6TG)-resistant mutations induced by 4-nitroquinolin 1-oxide (4NQO) were found in cultured Chinese hamster V79 cells. The antimutagenic activity of catechins was found only when cells were post-treated with catechins during the mutation expression time after treatment with 4NQO, and not found by simultaneous treatments with 4NQO and catechins. This bioantimutagenic activity of catechins were not observed in ethyl methanesulfonate (EMS)-induced mutations. This suggests that the antimutagenic effects of catechins may act intracellularly as bio-antimutagenic blocking agent or suppressive agent. These catechins had no effects on the cytotoxic activity of 4NQO in V79 cells, whether catechins were used in simultaneous treatment with or in post-treatment after 4NQO. This indicates that the antimutagenicity and anticytotoxicity to 4NQO may be caused by different mechanism(s).
246. Nutr Cancer. 1996;26(3):325-35.
Prevention of photocarcinogenesis by topical administration of pure epigallocatechin gallate isolated from green tea.
Gensler HL, Timmermann BN, Valcic S, Wachter GA, Dorr R, Dvorakova K, Alberts DS.
Arizona Cancer Center, Department of Radiation Oncology, USA.
Topical application of purified (-)-epigallocatechin-3-gallate (EGCG), a polyphenolic antioxidant isolated from green tea, inhibited photocarcinogenesis in BALB/cAnNHsd mice with no visible toxicity. Mice were treated with 0, 10, or 50 mg of EGCG in 200 microliters of acetone three times weekly for three weeks before ultraviolet (UV) treatments began and throughout the experiment. UV radiation consisted of five 30-minute exposures per week to banks of six FS40 Westinghouse sunlamps for 25 weeks. In the photocarcinogenesis study, mice received a total dose of approximately 2.1 x 10(6) J/m2. Skin cancer incidence in UV-irradiated mice was 96% at 28 weeks after the first UV treatment; EGCG at 10 or 50 mg reduced this incidence to 62% and 29%, respectively. UV-induced immunosuppression, assessed by the inability of UVB-irradiated mice to reject a syngeneic antigenic tumor, was not influenced by topical EGCG. Oral administration of 0, 100, or 500 mg of pure EGCG per liter of drinking water (approximately 0, 0.56, or 2.8 mg/day, respectively) did not decrease UV-induced skin tumor incidence, rate of primary tumor growth, or inability to reject antigenic tumors. Thus induction of skin tumors by UV radiation was significantly reduced by topical, but not by oral, administration of purified EGCG through a mechanism distinct from inhibition of photoimmunosuppression.
247. FEMS Microbiol Lett 1996 Sep 15;143(1):35-40
Peroxidase-catalyzed generation of catechin oligomers that inhibit glucosyltransferase from Streptococcus sobrinus.
Hamada S, Kontani M, Hosono H, Ono H, Tanaka T, Ooshima T, Mitsunaga T, Abe I
Department of Oral Microbiology, Osaka University Faculty of Dentistry, Suita-Osaka, Japan.
Oolong tea extract (OTE) and the purified polymeric polyphenols from OTE have been found to inhibit glucosyltransferase (GTase) of mutans streptococci. In view of the partial fermentation characteristic of oolong tea, we describe here an in vitro model reaction system to produce partially fermented products of D-(+)-catechin or green tea extract (GTE) using horseradish peroxidase. A dimeric catechin molecule was identified as dehydro-dicatechin A by instrumental analyses. The molecular size of some oligomeric catechins was estimated by the elution profile with HPLC. These catechin oligomers markedly inhibited GTase from Streptococcus sobrinus 6715. As the degree of polymerization of catechin or GTE increased, GTase was inhibited more effectively. These results suggest that polymeric polyphenols found in OTE are synthesized by partial fermentation due to oxidases/peroxidases present in tea leaves.
248. Anticancer Drugs. 1996 Jun;7(4):461-8.
Inhibitory effect of six green tea catechins and caffeine on the growth of four selected human tumor cell lines.
Valcic S, Timmermann BN, Alberts DS, Wachter GA, Krutzsch M, Wymer J, Guillen JM.
Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson 85721, USA.
Green tea is an aqueous infusion of dried unfermented leaves of Camellia sinensis (family Theaceae) from which numerous biological activities have been reported including antimutagenic, antibacterial, hypocholesterolemic, antioxidant, antitumor and cancer preventive activities. From the aqueous-alcoholic extract of green tea leaves, six compounds (+)-gallocatechin (GC), (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin gallate (EGCG) and caffeine, were isolated and purified. Together with (+)-catechin, these compounds were tested against each of four human tumor cells lines (MCF-7 breast carcinoma, HT-29 colon carcinoma, A-427 lung carcinoma and UACC-375 melanoma). The three most potent green tea components against all four tumor cell lines were EGCG, GC and EGC. EGCG was the most potent of the seven green tea components against three out of the four cell lines (i.e. MCF-7 breast cancer, HT-29 colon cancer and UACC-375 melanoma). On the basis of these extensive in vitro studies, it would be of considerable interest to evaluate all three of these components in comparative preclinical in vivo animal tumor model systems before final decisions are made concerning which of these potential chemopreventive drugs should be taken into broad clinical trials.
249. Biosci Biotechnol Biochem 1996 Jun;60(6):1000-5
Effectiveness of green tea tannin on rats with chronic renal failure.
Yokozawa T, Chung HY, He LQ, Oura H. Research Institute for Wakan-Yaku, Toyama Medical and Pharmaceutical University, Japan.
The effects of green tea tannin on nephrectomized rats were examined. There were increases in blood urea nitrogen, serum creatinine, and urinary protein, and a decrease in creatinine clearance in the nephrectomized control rats, whereas better results for these parameters were obtained in rats given green tea tannin after nephrectomy, demonstrating a suppressed progression of the renal failure. When the renal parenchyma was partially resected, the remnant kidney showed a decrease in the activity of radical scavenger enzymes. Green tea tannin, however, was found to lighten the kidney under such oxidative stress. Mesangial proliferation and glomerular sclerotic lesions, which were conspicuous in the rats that were not given green tea tannin after nephrectomy, were also relieved.
250. Cancer. 1996 Apr 15;77(8 Suppl):1662-7.
Inhibitory effects and toxicity of green tea polyphenols for gastrointestinal carcinogenesis.
Yamane T, Nakatani H, Kikuoka N, Matsumoto H, Iwata Y, Kitao Y, Oya K, Takahashi T.
First Department of Surgery, Kyoto Prefectural University of Medicine, Japan.
BACKGROUND. Recently, and epidemiologic study showed a lower risk of gastrointestinal carcinogenesis in green tea drinkers. An experiment on two-stage skin carcinogenesis in mice showed that (-)-epigallocatechin gallate (EGCG), one of the main constituents of green tea, inhibited tumor formation. METHODS. The inhibitory effects of EGCG and green tea extract (GTE) on N-ethyl-N'-nitro-N-nitroguanidine (ENNG)-induced duodenal carcinogenesis in the mouse, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced carcinogenesis of the glandular stomach in the rat, and azoxymethane-induced colon carcinogenesis in the rat were examined. The toxicity of GTE was assessed experimentally and GTE was applied clinically in normal volunteers to determine the effective dose and to assess its harmful effects. RESULTS. EGCG and GRE inhibited chemical carcinogenesis of the gastrointestinal tract in rodents. Judging from the epidemiologic and experimental findings, it was determined that 1 g per day of GTE might be an effective dose. GTE was not toxic and no harmful effect was found during its clinical use. CONCLUSIONS. These findings suggest that EGCG and GTE are useful in preventing gastrointestinal carcinogenesis, and the clinical usefulness of GTE, which has no harmful effects and is inexpensive, should be studied further.
251. ree Radic Res. 1996 Mar;24(3):225-10.
Oxidation of caffeine and related methylxanthines in ascorbate and polyphenol-driven Fenton-type oxidations.
Stadler RH, Richoz J, Turesky RJ, Welti DH, Fay LB.
Nestec Ltd., Nestle Research Centre, Lausanne, Switzerland.
Caffeine and related methylxanthines were subjected to free radical mediated oxidation by incubation with Fe(3+)-EDTA/ascorbate and Fe(3+)-EDTA/polyphenolics. The reaction mixtures were analysed by reverse-phase HPLC, revealing the corresponding C-8 hydroxylated analogues as the major products of hydroxyl radical mediated attack. Further oxidation products of caffeine, analysed by liquid chromatography-mass spectrometry (LC-MS), were the N1-, N3- and N7-demethylated methylxanthine analogues theobromine, paraxanthine and theophylline, respectively. Isolable amounts of the imidazole ring operated 6-amino-5-(N-formylmethyl-amino)-1,3-dimethyl-uracil (1,3,7-DAU) derivative were also detected, which was characterised by 1H NMR and mass spectroscopy. The identified products indicate that the pertinent chemical reactions, i.e. C-8 hydroxylation, demethylations, and C8-N9 bond scission, are comparable to the primary metabolic pathways of caffeine in humans. The influence of pH, transition metals, hydrogen peroxide, free radical scavengers and metal chelators on caffeine oxidation was studied. This report illustrates that natural food-borne reactants can aid in identifying specific chemical markers of free radical induced damage. Furthermore, potentially anti-and pro-oxidative reactions can be elucidated which may be important in assessing the impact of nutrient additives and supplements on the shelf life and stability of foods and beverages.
252. Mutagenesis 1996 Mar;11(2):189-94
Antimutagenicity and catechin content of soluble instant teas.
Constable A, Varga N, Richoz J, Stadler RH
Nestec Ltd Research Centre, Vers-Chez-les-Blanc, Lausanne, Switzerland.
The antimutagenic properties of soluble instant teas were examined using the bacterial Ames assay. Inhibition of the numbers of revertants induced from a number of known mutagens indicates that aqueous extracts of instant teas have antimutagenic activity and antioxidative properties, and can inhibit nitrosation reactions. Despite a significant reduction in the amounts of major green tea catechins, quantified using reversed-phase HPLC with electro-chemical detection, no differences in antimutagenicity were observed between the instant teas, a black fermented tea and a green tea. Oxidation of polyphenolic compounds which occurs during the production of instant tea does not therefore decrease the antioxidant, free radical scavenging and antimutagenic properties. This suggests that catechins are not the only compounds responsible for the protective effects of teas.
253. Fundam Appl Toxicol. 1996 Feb;29(2):244-50.
Chemopreventive effects of green and black tea on pulmonary and hepatic carcinogenesis.
Cao J, Xu Y, Chen J, Klaunig JE.
Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis 46202-5196, USA.
The chemopreventive effects of decaffeinated green and black tea treatment on liver and lung tumorigenesis were examined in carcinogen-treated mice. Male C3H mice were given decaffeinated green or decaffeinated black tea in their drinking water prior to, during, and after treatment with diethylnitrosamine (50 micrograms/kg bw, i.p., once per week for 8 weeks). After 40 weeks of tea treatment, mice were sampled and examined for pulmonary and hepatic tumors. Mice treated with both DENA and tea displayed a significant decrease in the mean number of lung and liver tumors compared to DENA-only treated animals. Mice that received 0.63 or 1.25% green tea or 1.25% black tea exhibited a reduction in liver tumor numbers of 54, 50, and 63%, respectively from that seen in the DENA-only treated mice. Tea treatment also significantly decreased the multiplicity of lung adenomas. Mice receiving DENA and either 0.63 or 1.25% green tea or 1.25% black tea showed a decrease in the mean number of lung tumors of 40, 46, and 34%, respectively, from DENA-only treated mice. While a possible association between the chemopreventive activity of tea on lung tumor response and the concentration of (-) epigallocatechin gallate (EGCG) in the tea was suggested, no apparent relationship between EGCG concentration and liver tumor response was seen, however. These results show a dose-dependent chemoprevention of both lung and liver tumors by both black and green tea in diethylnitrosamine-treated C3H mice.
254. Natl Cancer Inst 1996 Jan 17;88(2):93-100
Consumption of black tea and cancer risk: a prospective cohort study.
Goldbohm RA, Hertog MG, Brants HA, van Poppel G, van den Brandt PA
Department of Epidemiology, Netherlands Organization for Applied Scientific Research [TNO] Nutrition and Food Research Institute, Zeist, The Netherlands.
BACKGROUND: Tea is one of the most frequently consumed beverages in the world. Antioxidant polyphenol compounds (such as catechins and flavonols) are abundantly present in both green and black teas and have been observed to have anticarcinogenic properties in cell and animal model studies. In black tea, however, most of the catechins have been oxidized to forms that may have reduced anticarcinogenic properties. Despite indications from experimental studies that tea may protect against cancer, epidemiologic evidence has been inconclusive. PURPOSE: The association between black tea consumption and the subsequent risk of stomach, colorectal, lung, and breast cancers was investigated in The Netherlands Cohort Study on Diet and Cancer among 58,279 men and 62,573 women aged 55-69 years. METHODS: Subjects in the cohort completed a self-administered questionnaire on dietary habits and other risk factors for cancer at base line in 1986. Follow-up for cancer was done by means of computerized record linkage with all nine regional cancer registries in The Netherlands and the national pathology database. During 4.3 years of follow-up, 200, 650, 764, and 650 cases of stomach, colorectal, lung, and breast cancers were diagnosed, respectively. The questionnaire data of case subjects and those of a random subcohort (n = 3500) were used to calculate rate ratios (RRs) of cancer in categories of consumers of black tea compared with nonconsumers. RESULTS: Tea was not used by 13% of the subjects in the cohort, whereas 37%, 34%, and 16% consumed one to two, three to four, and five or more cups of tea per day, respectively. No association was observed between tea consumption and risk of colorectal cancer: The risk among tea drinkers in each consumption category was similar to that among nondrinkers. The RR of breast cancer among consumers of five or more cups of tea per day was 1.3 (95% confidence interval = 0.9-2.0); no dose-response association was observed. In age- and sex-adjusted analyses, consumption of tea was inversely associated with stomach (two-sided P for trend = .147) and lung (two-sided P for trend < .001) cancers. However, tea drinkers appeared to smoke less and to eat more vegetables and fruits than nondrinkers. When smoking and dietary factors were taken into account, tea in itself did not appear to protect against stomach and lung cancers: The RRs in all consumption categories were close to unity. Analysis of the tea and cancer relationship in a subgroup that included subjects in the lowest two quintiles of consumption of vegetables and fruits also failed to reveal a protective effect of tea consumption on the risk of three cancer types studied (colorectal, lung, and breast cancers). CONCLUSIONS: This investigation does not support the hypothesis that consumption of black tea protects against four of the major cancers in humans; a cancer-enhancing effect was not evident, either.
255. Mutagenesis 1996 Jan;11(1):37-41
Relationship between antimutagenic activity and major components of various teas.
Yen GC, Chen HY
Department of Food Science, National Chung Hsing University, Taichung, Taiwan, Republic of China.
The objectives of this study were to determine the major components in tea leaves and tea extracts and to study the relationship between chemical content and antimutagenic activity of various tea extracts. The amount of catechins in various tea extracts was in the order: green tea (26.7%) > oolong tea (23.2%) > pouchong tea (15.8%) > black tea (4.3%). The amounts of caffeine and phenolic compounds in oolong tea extracts were 8.3 and 32.4%, respectively; these amounts were greater than those in the other three tea extracts. The ascorbic acid in green tea extracts was a little higher than in oolong and pouchong tea extracts. The amount of catechins in tea leaves also showed the order: nonfermented (green tea) > semifermented (pouchong tea and oolong tea) > fermented tea (black tea). The amounts of caffeine and phenolic compounds in oolong tea leaves are also higher than in other tea leaves. Besides water soluble components, tea leaves also contain several lipid soluble chemicals such as beta-carotene and tocopherols. The tea extracts, especially oolong and pouchong teas, markedly inhibited the mutagenicity of 2-amino-3-methylimidazo (4,5-f)quinoline (IQ), 3-amino-1,4-dimethyl-5H-pyrido-(4,3-b)indole (Trp-P-1), 2-amino-6-methyl-dipyrido(1,2-a:3',2'-d) imidazole (Glu-P-1), benzo[a]pyrene (B[a]P) and aflatoxin B1 (AFB1). The inhibitory effect of tea extracts against the mutagenicity of IQ and Glu-P-1 in Salmonella typhimurium TA100 showed a significant (P < 0.05) correlation to the contents of catechins and ascorbic acid. The antimutagenic activity of tea extracts to Trp-P-1 in TA98 or TA100 was well correlated (P < 0.05) to the caffeine contents. No significant (P > 0.05) correlation was found between the antimutagenicity of tea extracts to B[a]P and AFB1 in TA100 and the content of major components in tea extracts.
256. Cancer Causes Control. 1996 Jan;7(1):33-40.
Nutrition and esophageal cancer.
Cheng KK, Day NE.
Department of Public Health and Epidemiology, University of Birmingham, United Kingdom.
Epidemiologic evidence on the relation between nutrition and esophageal cancer is reviewed. Results from ecologic, case-control, cohort, and intervention studies are included. Most of the findings pertain more to squamous cell carcinoma than adenocarcinoma of the esophagus. The protective effect of fruit and vegetable consumption is supported by a large body of evidence, especially from case-control studies. The effects of food groups and nutrients other than fruits and vegetables also have been examined, but the overall evidence is less convincing. Recent intervention studies in high incidence areas in China indicate that micronutrient supplements may have a modest effect in reducing risk, but the generalizability of this result is uncertain. Hot drinks are likely to increase the risk of esophageal cancer. On the other hand, the role of tea drinking, especially the use of green tea, remains to be defined better.
257. Biosci Biotechnol Biochem 1996 Jan;60(1):169-70
Effects of green tea and tea catechins on the development of mammary gland.
Sayama K, Ozeki K, Taguchi M, Oguni I
Department of Animal Science, Shizuoka University, Japan.
To find whether green tea and tea catechins have effects on the development of mammary glands, virgin DDD mice were fed on diets containing green tea and tea catechins. The degree of mammary gland development was examined by duct-alveolar growth and DNA content. The results indicated that green tea, but not tea catechins, has a growth-promoting effect on mammary gland development.
258. Carcinogenesis 1995 Dec;16(12):3049-55
Inhibitory effects of 1-O-hexyl-2,3,5-trimethylhydroquinone (HTHQ), green tea catechins and other antioxidants on 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1)-induced rat hepatocarcinogenesis and dose-dependent inhibition by HTHQ of lesion induction by Glu-P-1 or 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx).
Hirose M, Hasegawa R, Kimura J, Akagi K, Yoshida Y, Tanaka H, Miki T, Satoh T, Wakabayashi K, Ito N, et al
First Department of Pathology, Nagoya City University, Medical School, Japan.
The effects of 1-O-hexyl-2,3,5-trimethylhydroquinone (HTHQ), green tea catechins (GTC), alpha-tocopherol, beta-carotene, chlorophyllin, phenylethylisothiocyanate (PEITC), 3-O-ethylascorbic acid (EAsA), 3-O-dodecylcarbomethyl ascorbic acid (DAsA), n-tritriacontane-16,18-dione (TTAD) and d-limonene on 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1)- or dimethylnitrosamine (DMN)-induced hepatocarcinogenesis, and the dose dependence of HTHQ inhibition of Glu-P-1- or 2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline (MeIQx)-influence on lesion development were examined in a rat medium-term liver bioassay system featuring diethylnitrosamine initiation and partial hepatectomy. At the end of week 8, the number and total area of glutathione S-transferase placental form (GST-P) positive liver foci in rats treated with 0.03% Glu-P-1 alone were increased significantly (46.8 +/- 11.0 and 12.0 +/- 5.6 respectively) as compared to the control values (3.8 +/- 1.6 and 0.4 +/- 0.2). Combined treatment with 1% HTHQ remarkably reduced both of these parameters (8.1 +/- 2.1 and 0.6 +/- 0.2). GTC (1%), PEITC (0.1%), beta-carotene (0.1%) and DAsA (1%) also demonstrated inhibition but less than HTHQ. On the other hand, these antioxidants did not influence development of foci initiated by 0.002% DMN. In the dose-response study, up to 0.125% HTHQ significantly reduced the effects of 0.02% Glu-P-1 or 0.03% MeIQx on the number and area of foci. These results indicate that several antioxidants exert chemopreventive effects against heterocyclic amine (HCA)-induced hepatocarcinogenesis, and particularly HTHQ which thus deserves further attention as a chemopreventor in the contest of the environmentally important HCA group of carcinogens.
259. Cancer Lett 1995 Nov 27;98(1):27-31
Inhibitory effects of green tea infusion on in vitro invasion and in vivo metastasis of mouse lung carcinoma cells.
Sazuka M, Murakami S, Isemura M, Satoh K, Nukiwa T
School of Food and Nutritional Sciences, University of Shizuoka, Japan.
The peroral administration of green tea infusion reduced the number of lung colonies of mouse Lewis lung carcinoma cells in a spontaneous metastasis system. The experiments with artificially reconstituted basement membrane suggested that this reduction could be understood by the inhibitory effects of the green tea infusion and its constituent catechins on the penetration of the cells through the basement membrane.
260. Cancer Lett 1995 Sep 25;96(2):239-43
Growth inhibition and regression of human prostate and breast tumors in athymic mice by tea epigallocatechin gallate.
Liao S, Umekita Y, Guo J, Kokontis JM, Hiipakka RA
Ben May Institute, Department of Biochemistry and Molecular Biology, University of Chicago, IL 60637, USA.
The human prostate cancer cell lines, PC-3 (androgen-insensitive) and LNCaP 104-R (androgen-repressed) were inoculated subcutaneously into nude mice to produce prostate tumors. Intraperitoneal injection of green tea (-)epigallocatechin-3-gallate but not structurally related catechins, such as (-)epicatechin-3-gallate, inhibited the growth and rapidly reduced the size of human prostate tumors in nude mice. (-)Epigallocatechin-3-gallate also rapidly inhibited the growth of tumor growth formed by the human mammary cancer cell line MCF-7 in nude mice. It is possible that there is a relationship between the high consumption of green tea and the low incidence of prostate and breast cancers in some Asian countries.
261. Biochem Biophys Res Commun 1995 Sep 25;214(3):833-8
Selective inhibition of steroid 5 alpha-reductase isozymes by tea epicatechin-3-gallate and epigallocatechin-3-gallate.
Liao S, Hiipakka RA
Ben May Institute, University of Chicago, IL 60637, USA.
Inhibitors of 5 alpha-reductase may be effective in the treatment of 5 alpha-dihydrotestosterone-dependent abnormalities, such as benign prostate hyperplasia, prostate cancer and certain skin diseases. The green tea catechins, (-)epigallocatechin-3-gallate and (-)epicatechin-3-gallate, but not (-)epicatechin and (-)epigallocatechin, are potent inhibitors of type 1 but not type 2 5 alpha-reductase. (-)Epigallocatechin-3-gallate also inhibits accessory sex gland growth in the rat. These results suggest that certain tea gallates can regulate androgen action in target organs.
262. Pancreas 1995 Aug;11(2):127-31
The effects of green tea catechins (Polyphenon) on DL-ethionine-induced acute pancreatitis.
Takabayashi F, Harada N, Hara Y
Hamamatsu College, University of Shizuoka, Japan.
The effects of green tea catechins (Polyphenon) on DL-ethionine-induced acute pancreatitis in rats were examined. The acute pancreatitis induced in this study was characterized by moderate inter- and intrastitial edema and patchy acinar cell necrosis. In rats induced with acute pancreatitis by an intraperitoneal injection of DL-ethionine, the wet weight of the pancreas (0.47 +/- 0.059 g/100 g body weight; p < 0.05), the serum amylase (10,432 +/- 996 IU/L; p < 0.001), and the tissue concentration of lipid peroxides (19.5 +/- 1.78 nmol/mg tissue DNA; p < 0.001) were significantly increased compared with values obtained in control rats (0.39 +/- 0.037 g/100 g body weight, 5,639 +/- 1,568 IU/L, and 10.7 +/- 1.04 nmol/mg tissue DNA, respectively) injected with isotonic saline. In contrast, in rats injected with DL-ethionine and supplied with a green tea catechin solution as a beverage instead of water during the experimental period, the tissue of pancreas was almost-correct, and the wet weight of the pancreas (0.39 +/- 0.054 g/100 g body weight; p < 0.05), the serum amylase (5,716 +/- 708 IU/L; p < 0.001), and the concentration of lipid peroxides in tissue (11.5 +/- 2.15 nmol/mg tissue DNA; p < 0.001) were significantly decreased compared with values obtained in rats injected with DL-ethionine and supplied with water as a beverage. These data suggest that green tea catechins may have a protective effect on the pathogenesis of experimental acute pancreatitis.
263. Arch Biochem Biophys 1995 Oct 1;322(2):339-46
Polyphenolic flavanols as scavengers of aqueous phase radicals and as chain-breaking antioxidants.
Salah N, Miller NJ, Paganga G, Tijburg L, Bolwell GP, Rice-Evans C
Radical Research Group, UMDS--Guy's Hospital, University of London, United Kingdom.
The purpose of this investigation was to establish the relative antioxidant activities in vitro of the flavanolic polyphenols, the catechins, and catechin-gallate esters. The relative antioxidant potentials were measured against radicals generated in the aqueous phase and against propagating lipid peroxyl radicals. The results show that in the aqueous phase their order of effectiveness as radical scavengers is epicatechin gallate (ECG) > epigallocatechin gallate (EGCG) > epigallocatechin (EGC) > gallic acid (GA) > epicatechin congruent to catechin; against propagating lipid peroxyl radical species, epicatechin and catechin are as effective as ECG and EGCG, the least efficacious being EGC and GA. This is consistent with their relative abilities to protect against consumption of LDL alpha-tocopherol. The results are discussed in the context of the most relevant antioxidant constituents of green tea extracts.
264. Carcinogenesis 1995 Feb;16(2):217-21
Chemoprevention of 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP)-induced mammary gland carcinogenesis by antioxidants in F344 female rats.
Hirose M, Akagi K, Hasegawa R, Yaono M, Satoh T, Hara Y, Wakabayashi K, Ito N
First Department of Pathology, Nagoya City University, Medical School, Japan.
Chemopreventive effects of the antioxidants 1-O-hexyl-2,3,5- trimethylhydroquinone (HTHQ), 3-O-ethylascorbic acid (EAsA), 3-O-dodecylcarbomethylascorbic acid (DAsA), green tea catechins (GTC) and ellagic acid on 2-amino-1-methyl-6- phenylimidazo[4,5-b]pyridine (PhIP)-induced mammary carcinogenesis were examined in female F344 rats. Groups of 20-21 6-week-old rats were maintained on a powdered diet containing 0.02% PhIP alone, PhIP together with 0.5% HTHQ, 1% EAsA, 1% DAsA, 1% GTC or 0.1% ellagic acid, these antioxidants alone or basal diet alone without supplement for 52 weeks. The survival rates of PhIP plus antioxidant groups at the end of the experiment were higher than that of the PhIP alone group. Sequential observation of palpable mammary tumors demonstrated only one tumor by week 52 in the PhIP plus HTHQ group, whereas 40% of the rats receiving PhIP alone had tumors by this time point. The final incidence of mammary adenocarcinomas was significantly decreased in the PhIP plus HTHQ group (4.8%, P < 0.01) as compared to the PhIP alone value (40%). Although statistically not significant, incidences of adenocarcinomas in the other antioxidant-treated groups (23.8-28.6%) were also lower than in the PhIP alone group. Furthermore, the incidence of large intestinal tumors in the PhIP plus HTHQ group (0%) showed a tendency to decrease relative to the PhIP alone group (16.7%). These results indicate that antioxidants, particularly HTHQ, exert a potent chemopreventive action against PhIP-induced carcinogenesis.
265. J Cell Biochem Suppl. 1995;22:169-80.
Polyphenols as cancer chemopreventive agents.
Stoner GD, Mukhtar H.
Department of Preventive Medicine, Ohio State University, Columbus 43210, USA.
This article summarizes available data on the chemopreventive efficacies of tea polyphenols, curcumin and ellagic acid in various model systems. Emphasis is placed upon the anticarcinogenic activity of these polyphenols and their proposed mechanism(s) of action. Tea is grown in about 30 countries and, next to water, is the most widely consumed beverage in the world. Tea is manufactured as either green, black, or oolong; black tea represents approximately 80% of tea products. Epidemiological studies, though inconclusive, suggest a protective effect of tea consumption on human cancer. Experimental studies of the antimutagenic and anticarcinogenic effects of tea have been conducted principally with green tea polyphenols (GTPs). GTPs exhibit antimutagenic activity in vitro, and they inhibit carcinogen-induced skin, lung, forestomach, esophagus, duodenum and colon tumors in rodents. In addition, GTPs inhibit TPA-induced skin tumor promotion in mice. Although several GTPs possess anticarcinogenic activity, the most active is (-)-epigallocatechin-3-gallate (EGCG), the major constituent in the GTP fraction. Several mechanisms appear to be responsible for the tumor-inhibitory properties of GTPs, including enhancement of antioxidant (glutathione peroxidase, catalase and quinone reductase) and phase II (glutathione-S-transferase) enzyme activities; inhibition of chemically induced lipid peroxidation; inhibition of irradiation- and TPA-induced epidermal ornithine decarboxylase (ODC) and cyclooxygenase activities; inhibition of protein kinase C and cellular proliferation; antiinflammatory activity; and enhancement of gap junction intercellular communication. Curcumin is the yellow coloring agent in the spice turmeric. It exhibits antimutagenic activity in the Ames Salmonella test and has anticarcinogenic activity, inhibiting chemically induced preneoplastic lesions in the breast and colon and neoplastic lesions in the skin, forestomach, duodenum and colon of rodents. In addition, curcumin inhibits TPA-induced skin tumor promotion in mice. The mechanisms for the anticarcinogenic effects of curcumin are similar to those of the GTPs. Curcumin enhances glutathione content and glutathione-S-transferase activity in liver; and it inhibits lipid peroxidation and arachidonic acid metabolism in mouse skin, protein kinase C activity in TPA-treated NIH 3T3 cells, chemically induced ODC and tyrosine protein kinase activities in rat colon, and 8-hydroxyguanosine formation in mouse fibroblasts. Ellagic acid is a polyphenol found abundantly in various fruits, nuts and vegetables. Ellagic acid is active in antimutagenesis assays, and has been shown to inhibit chemically induced cancer in the lung, liver, skin and esophagus of rodents, and TPA-induced tumor promotion in mouse skin.
266. The tea plant - Camellia sinensis (L.)O. Kuntze CAMELLIA SINENSIS (L.) O. KUNTZE. DER TEESTRAUCH Scholz E.; Bertram B. Inst. fur Pharmazeutische Biologie, Albert-Ludwigs-Universitat, Schanzlestrasse 1, 79104 Freiburg Germany Zeitschrift fur Phytotherapie (Germany) , 1995, 16/4 (231-238+241-246)
The worldwide consumption of tea as a beverage is second only to that of water. Tea is obtained from young leaves and buds of Camellia sinensis (L.) O. Kuntze, indigenous to mountainous regions of Southeast Asia and cultivated in East Asia for more than 2000 years. green tea is manufactured by rapid heating followed by drying of freshly harvested leaves. Fermentation of the withered, rolled and crushed fresh leaves at high humidity gives black tea. Besides caffeine, which is present in both tea qualities, green tea contains high quantities of flavanols (catechins), flavonol glycosides, small amounts of condensed and hydrolysable tannins, and saponins. Tannin related, coloured oxidation products of flavanols, particularly the poorly characterized thearubigens, prevail in black tea, which also contains theaflavins, small amounts of theaflagallins and bisflavanols (theasinensins), and unchanged flavonol glycosides. In both tea qualities, unusually high levels of fluorides and aluminium are found. Consumption of green and black tea has been reported to be beneficial to human health. Many laboratory studies have demonstrated inhibitory effects of tea preparations and tea polyphenols against tumor formation and growth, and there is some evidence from epidemiologic studies, that tea may have a protective effect on certain cancers. This effect is believed to be mainly due to antioxidative properties of the tea polyphenols, coupled with their ability to inhibit carcinogen activating enzymes and to suppress endogenous formation of N-nitroso compounds. In addition, virostatic, bacteristatic and reverse-transcriptase-inhibitive, as well as antiatherosclerotic effects are reported. Green tea extracts and flavanols decrease blood pressure, plasma glucose and cholesterol levels in vivo, inhibit platelet aggregation in vitro, and seem to lower the risk of coronary heart disease.
267. Chest 1994 Dec;106(6):1801-5
Epigallocatechin gallate. The major causative agent of green tea-induced asthma.
Shirai T, Sato A, Hara Y
Department of Internal Medicine, Hamamatsu University School of Medicine, Japan.
We describe three patients who worked in green tea factories and developed asthmatic and nasal symptoms after exposure to green tea dust. To clarify what component(s) of green tea leaves might be responsible for causing asthma, we prepared catechins, the major components of green tea leaves. Epigallocatechin gallate (EGCg; MW: 458 daltons), a major catechin, was purified by high-performance liquid chromatography. Subjects included three patients with green tea-induced asthma, five asthmatics with no previous exposure to tea dust, and five healthy controls. It was found that all three patients exhibited an immediate skin and bronchial response to EGCg. Prausnitz-Kustner test with EGCg was also positive. However, none of the asthmatic and healthy controls showed a positive reaction. These results indicate that EGCg is a causative agent of green tea-induced asthma and suggest that an IgE-mediated response is, at least in part, responsible for causing this type of occupational asthma.
268. Plant Foods Hum Nutr. 1994 Oct;46(3):221-9.
Green and black tea consumption by humans: impact on polyphenol concentrations in feces, blood and urine.
He YH, Kies C.
Department of Nutritional Science and Dietetics, University of Nebraska, Lincoln 68583-0807.
The objective of the study was to determine the effects of green tea, black tea and decaffeinated black tea consumption on urinary and fecal excretions and whole blood and blood serum concentrations of polyphenols. The 56 day study was divided into four randomly arranged experimental periods of 14 days each during which the 10 healthy adult subjects consumed a laboratory controlled, constant, measured diet based on ordinary foods. During separate periods, subjects received no tea, green tea, regular black tea or decaffeinated black tea beverages at the three daily meals. Subjects made complete collections of urine and stools throughout the study and fasting blood samples were drawn at the beginning of the study and at the end of each experimental period. Polyphenols contained in urine, feces, whole blood, blood serums, food and tea were analyzed by the spectrophotometry method of Wah Lau et al. (1989). Green tea consumption resulted in highest intakes in greatest fecal and urinary excretions, highest retentions, and high whole blood concentrations of polyphenols followed by effects of regular black tea, decaffeinated black tea and no tea treatments. These results indicate that polyphenols from tea are at least partly absorbable. Hence, both positive and negative effects of dietary polyphenol may occur internal to the body proper and not only as effects within the intestines.
269. Cancer Lett 1994 Aug 15;83(1-2):149-56
Inhibition of mammary gland carcinogenesis by green tea catechins and other naturally occurring antioxidants in female Sprague-Dawley rats pretreated with 7,12-dimethylbenz[alpha]anthracene.
Hirose M, Hoshiya T, Akagi K, Futakuchi M, Ito N
First Department of Pathology, Nagoya City University, Medical School, Japan.
Effects of the naturally occurring antioxidants on mammary gland carcinogenesis were examined in female Sprague-Dawley rats pretreated with 7,12-dimethylbenz[alpha]anthracene (DMBA). Groups of 15-16 7-week-old rats received a 50 mg/kg body weight intra-gastric dose of DMBA, and starting one week thereafter placed on diet containing 0.4% catechol, 1.0% gamma-oryzanol, 2.0% phytic acid, 1.0% green tea catechins (GTC), 1.0% tannic acid or basal diet alone for 35 weeks. Although the final incidences and multiplicities of mammary tumors were not significantly different between DMBA-treated groups, the numbers of survivors in the antioxidant-treated groups at the end of the experiment at week 36 were significantly higher than in the basal diet group. In particular, the survival rate of the GTC group at 93.8% strongly contrasted with that of only 33.3% for rats on the basal diet. At the end of week 18, when all the animals were still alive, the average size of palpable mammary tumors was significantly smaller in the catechol, phytic acid and catechins groups. These results indicate that antioxidants, and GTC in particular, inhibit rat mammary gland carcinogenesis after DMBA initiation.
270. Cancer Lett 1994 Apr 29;79(1):33-8
Experimental studies of the inhibitory effects of green tea catechin on mice large intestinal cancers induced by 1,2-dimethylhydrazine.
Yin P, Zhao J, Cheng S, Zhu Q, Liu Z, Zhengguo L
Department of Pathology, Henan Provincial Hospital, China.
Three hundred Kunming mice were randomly divided into six groups (half males and half females in each group). Group 1 was the positive control group, Groups 2, 3, 4 and 5 were experimental groups and Group 6 was used as the solvent control group. Mice in Groups 1-4 were injected with 1,2-dimethylhydrazine (1,2-DMH) (20 mg/kg body wt.) solution subcutaneously once a week from the 2nd week to the 20th week. From the 1st week to the 23rd week, mice in Groups 2, 3 and 4 were given catechin (1 mg/mouse), catechin (2 mg/mouse) and EGCG (2 mg/mouse), respectively, five times a week. Mice in Group 5 received only catechin (3 mg/mouse) five times a week from the 1st to the 23rd week. Mice in Group 6 were injected with an equal volume of 1 mmol EDTA solution subcutaneously once a week from the 2nd to the 20th week. At the end of the 27th week, all the mice were killed by cervical dislocation (Zhu, Q.H. and Zhu, Q.F. (1991) Laboratory Animal Science, 1st edition. The Junior Educational Publisher, Guangdong). Pathological examinations indicated that the incidence of large intestinal cancers occurring in Group 1 was 80%, significantly higher than that in Groups 2, 3 and 4 (p < 0.001). No tumors were found in Groups 5 and 6. This might suggest that green tea has preventive effects on large intestinal cancer induction in spite of the different doses of catechin. Immunohistochemistry studies showed that green tea catechins could enhance the activity of superoxide dismutase (SOD) in tissues.
271. Cancer Res. 1994 Jul 1;54(13):3428-35.
Inhibitory effects of black tea, green tea, decaffeinated black tea, and decaffeinated green tea on ultraviolet B light-induced skin carcinogenesis in 7,12-dimethylbenz[a]anthracene-initiated SKH-1 mice.
Wang ZY, Huang MT, Lou YR, Xie JG, Reuhl KR, Newmark HL, Ho CT, Yang CS, Conney AH.
Department of Chemical Biology and Pharmacognosy, College of Pharmacy, Rutgers, State University of New Jersey, Piscataway 08855-0789.
In a previous study (Z. Y. Wang et al., Cancer Res., 52: 1162-1170, 1992), we found that administration of a water extract of green tea leaves as the sole source of drinking fluid inhibited ultraviolet B light (UVB)-induced carcinogenesis in SKH-1 mice previously initiated with 7,12-dimethylbenz[a]anthracene (DMBA). In the present study, we compared the effects of black tea, green tea, decaffeinated black tea, and decaffeinated green tea on UVB-induced skin carcinogenesis in DMBA-initiated SKH-1 mice. A 1.25% water extract of each kind of tea leaf (1.25 g tea leaf/100 ml water) was prepared by passing 4 liters of hot water through 50 g of tea leaves in a Bunn tea brewing machine. The mean concentrations of solids in multiple samples of 1.25% black tea, green tea, decaffeinated black tea, and decaffeinated green tea analyzed during the course of this study were 4.23, 3.94, 3.66, and 3.53 mg/ml, respectively. These concentrations of tea solids are similar to those present in tea brews ingested by humans. Female SKH-1 mice were treated topically with 200 nmol of DMBA, followed 3 weeks later by irradiation with 30 mJ/cm2 of UVB twice weekly for 31 weeks. UVB-induced formation of skin tumors was markedly inhibited by oral administration of 0.63 or 1.25% black tea, green tea, decaffeinated black tea, or decaffeinated green tea as the sole source of drinking fluid 2 weeks prior to and during 31 weeks of UVB treatment. Administration of each of the eight tea preparations not only inhibited the number of tumors, but tumor size was also markedly decreased. Histopathological examination of each tumor showed that oral administration of the eight tea preparations had a marked inhibitory effect on the formation of UVB-induced keratoacanthomas and carcinomas. Administration of 1.25% black tea, green tea, decaffeinated black tea, or decaffeinated green tea inhibited the number of keratoacanthomas per mouse by 79, 78, 73, or 70%, respectively, and the number of carcinomas per mouse was inhibited by 93, 88, 77, or 72%, respectively. In summary, administration of black tea was comparable to green tea as an inhibitor of UVB-induced skin carcinogenesis in DMBA-initiated SKH-1 mice. Oral administration of decaffeinated black tea or decaffeinated green tea also had a marked inhibitory effect on UVB-induced skin carcinogenesis in DMBA-initiated SKH-1 mice, but these tea preparations were slightly less effective than the regular teas at the high dose level.
272. Carcinogenesis 1993 Aug;14(8):1549-53
Effects of green tea catechins in a rat multi-organ carcinogenesis model.
Hirose M, Hoshiya T, Akagi K, Takahashi S, Hara Y, Ito N
First Department of Pathology, Nagoya City University Medical School, Japan.
The effects of dietary administration of green tea catechins (GTC) were examined using a multi-organ carcinogenesis model. Groups of 15 F344 male rats were initially treated with a single i.p. administration of 100 mg/kg body wt N-diethyl-nitrosamine, 4 i.p. administrations of 20 mg/kg body wt N-methylnitrosourea, 4 s.c. doses of 40 mg/kg body wt 1,2-dimethylhydrazine, together with 0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine for 2 weeks and then 0.1% 2,2'-dihydroxy-di-n-propylnitrosamine for 2 weeks, both in the drinking water, for a total initiation period of 4 weeks. GTC in the diet, at doses of 1.0 or 0.1%, was administered from 1 day before and during carcinogen exposure, after carcinogen exposure or both during and after carcinogen exposure. Further groups of animals were treated with carcinogen, 1% GTC or basal diet alone as controls. All animals were killed at the end of week 36, and all major organs examined histopathologically. The numbers of small intestinal tumors (adenomas and carcinomas) per rat were significantly reduced in the groups treated with 1% GTC during (0.13 +/- 0.35) and after carcinogen exposure (0.31 +/- 0.48) and in those receiving 1% and 0.1% GTC both during and after carcinogen exposure (0.14 +/- 0.36, 0.46 +/- 0.97 respectively) as compared with the carcinogen alone group (1.07 +/- 1.21). On the other hand, numbers of glutathione S-transferase placental form positive liver foci per cm2 were slightly but significantly increased in the groups treated with 1 and 0.1% GTC during carcinogen exposure, 1% GTC after carcinogen exposure and 1% GTC both during and after carcinogen exposure. The results indicated that while GTC inhibits small intestinal carcinogenesis it slightly enhances hepatocarcinogenesis in a dose dependent manner when applied both during and after carcinogen exposure.
273. J Periodontol 1993 Jul;64(7):630-6
Inhibitory effect of tea catechins on collagenase activity.
Makimura M, Hirasawa M, Kobayashi K, Indo J, Sakanaka S, Taguchi T, Otake S
Nihon University School of Dentistry at Matsudo, Department of Clinical Pathology, Japan.
A major purpose of this study was to examine inhibitory effect of the catechin derivatives from Japanese green tea Camellia sinensis on collagenase activity. The crude tea catechins, which contain (+)-catechin (C), (-)-epicatechin (EC), (+)-gallocatechin (GC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), and (-)-epigallocatechin gallate (EGCg), were tested for their ability to inhibit the prokaryotic and eukaryotic cell derived collagenase activities. Among the tea catechins tested, ECg and EGCg showed the most potent inhibitory effect on collagenase activity when an optimal concentration of tea catechins (100 micrograms/ml) was added to reaction mixture containing collagenase and collagen. Preincubation of collagenase with tea catechins reduced the collagenase activity as well. In contrast to ECg and EGCg, the other four tea catechins (C, EC, EGC, and GC) did not show any collagenase inhibitory effect. Our results suggest that the steric structure of 3-galloyl radical is important for the inhibition of collagenase activity. The collagenase activity in the gingival crevicular fluid from highly progressive adult periodontitis was completely inhibited by the addition of tea catechins. These results demonstrated that tea catechins containing galloyl radical possess the ability to inhibit both eukaryotic and prokaryotic cell derived collagenase.
274. Carcinogenesis. 1993 May;14(5):849-55.
Protection against N-nitrosodiethylamine and benzo[a]pyrene-induced forestomach and lung tumorigenesis in A/J mice by green tea.
Katiyar SK, Agarwal R, Zaim MT, Mukhtar H.
Department of Dermatology, University Hospitals of Cleveland, Case Western Reserve University, OH.
In recent years we and others have shown the cancer chemopreventive effects of green tea in several animal tumor models. In this study we assessed the cancer chemopreventive effects of water extract of green tea (WEGT) and the polyphenolic fraction (GTP) isolated from WEGT against N-nitrosodiethylamine (DEN)- and benzo[a]pyrene (BP)-induced forestomach and lung tumorigenesis in A/J mice. The protective effects, both in forestomach and lungs, were evident by a decrease in number of tumors and the percentage of mice with tumors when WEGT and GTP were fed to animals during initiation, post-initiation and entire period of tumorigenesis protocols. Oral feeding of 0.2% GTP in drinking water to mice afforded 68-82 and 39-66% protection against DEN- and BP-induced forestomach tumorigenesis respectively. In case of pulmonary tumor multiplicity caused by DEN and BP, the protective effects of GTP were between 38-43 and 25-46% respectively. Similarly, oral feeding of 2.5% WEGT to mice also afforded 80-85 and 61-71% protection against DEN- and BP-induced forestomach tumorigenesis respectively. In case of lung tumorigenesis, the protective effects of WEGT were 43-62 and 25-51% respectively. Histological studies of forestomach tumors showed significantly lower squamous cell carcinoma counts in GTP- and WEGT-fed groups of mice compared to carcinogen alone treated control group of mice. When pulmonary tumors were examined histologically, no adenocarcinomas were observed in GTP- and WEGT-fed groups of mice compared to 20% mice with adenocarcinomas in carcinogen alone treated control group. Oral feeding of GTP and WEGT in drinking water also showed significant enhancement in the activities of glutathione S-transferase and NADP(H): quinone reductase in liver, small bowel, stomach and lung. The results of this study suggest that green tea possesses chemopreventive effects against carcinogen-induced tumorigenesis in internal body organs, and that the mechanism of such effects may involve the enhancement of phase II and anti-oxidant enzyme systems.
275. Cancer Lett. 1993 Apr 15;69(1):15-9.
Enhancement of gap junctional intercellular communication in tumor promoter-treated cells by components of green tea.
Sigler K, Ruch RJ.
Department of Pathology, Medical College of Ohio, Toledo 43699.
Green tea (Camellia sinensis) has been reported to inhibit tumor promotion in vivo and in vitro. Many tumor promoters inhibit gap junctional intercellular communication (GJIC) which may be an important mechanism of promotion. In the present study, we hypothesized that green tea would enhance GJIC in promoter-treated cells. An aqueous extract of green tea (GTE) and several of its constituents were tested for their effects on GJIC in p,p'-dichlorodiphenyltrichloroethane (DDT)-, 12-O-tetradecanoylphorbol-13-acetate (TPA)- and dieldrin-treated WB-F344 rat liver epithelial cells. All three promoters inhibited GJIC in a dose-responsive manner at non-cytolethal concentrations. (GTE (10-80 gamma/ml) enhanced GJIC 20-80% in promoter-treated cells. (-)-Epigallocatechin gallate and (-)-epicatechin gallate also enhanced GJIC in DDT-treated cells, but no effects were seen with (+)-catechin, (-)-epicatechin, (-)-epigallocatechin, caffeine, or theobromine. These data suggest GTE may inhibit tumor promotion by enhancing GJIC and that the most active components are the catechin gallates.
276, Biochim Biophys Acta 1993 Apr 8;1147(1):132-6
Bactericidal catechins damage the lipid bilayer.
Ikigai H, Nakae T, Hara Y, Shimamura T
Department of Molecular Life Science, Tokai University School of Medicine, Isehara, Japan.
The mode of antibacterial action of, the green tea (Camellia sinensis) extracts, (-)-epigallocatechin gallate (EGCg) and (-)-epicatechin (EC) was investigated. Strong bactericidal EGCg caused leakage of 5,6-carboxyfluorescein from phosphatidylcholine liposomes (PC), but EC with very weak bactericidal activity caused little damage to the membrane. Phosphatidylserine and dicetyl phosphate partially protected the membrane from EGCg-mediated damage when reconstituted into the liposome membrane with PC. EGCg, but not EC, caused strong aggregation and NPN-fluorescence quenching of PC-liposomes and these actions were markedly lowered in the presence of negatively charged lipids. These results show that bactericidal catechins primarily act on and damage bacterial membranes. The observation that Gram-negative bacteria are more resistant to bactericidal catechins than Gram-positive bacteria can be explained to some extent by the presence of negatively charged lipopolysaccharide.
277. Int J Immunopharmacol 1992 Nov;14(8):1399-407
Mitogenic activity of (-)epigallocatechin gallate on B-cells and investigation of its structure-function relationship.
Hu ZQ, Toda M, Okubo S, Hara Y, Shimamura T
Department of Microbiology and Immunology, Showa University School of Medicine, Tokyo, Japan.
(-)Epigallocatechin gallate (EGCg), the main constituent of green tea, strongly enhanced the direct plaque-forming cell (PFC) response to sheep red blood cells (SRBC) in vitro and showed strong mitogenic activity for mouse splenic B-cells but not for splenic T-cells and thymocytes. The enhancement of B-cell proliferation was not mediated by macrophages since their removal did not eliminate the activity. Among the derivatives of catechin examined, (+)catechin (C); (-)epicatechin (EC); (-)-epigallocatechin (EGC); (-)epicatechin gallate (ECg); (-)epigallocatechin gallate (EGCg); and theaflavin digallate (TF3), only the derivatives with the galloyl group (ECg, EGCg, and TF3) displayed significant enhancement of the spontaneous proliferation of B-cells. Structural analogs of the catechin and galloyl groups were also examined in the system. Gallic acid and tannic acid induced some enhancement, but rutin, pyrogallol and caffeine did not. The results indicate that the galloyl group on EGCg was responsible for enhancement. However, the basic conformations of the catechins are also important, because ECg, EGCg, TF3, gallic acid, and tannic acid had quite different potencies to induce B-cell proliferation.
278. Prev Med. 1992 May;21(3):361-9.
Inhibitory effect of green tea on tumorigenesis by chemicals and ultraviolet light.
Conney AH, Wang ZY, Huang MT, Ho CT, Yang CS.
Department of Chemical Biology and Pharmacognosy, College of Pharmacy, Rutgers, State University of New Jersey, Piscataway 08854.
Topical application of a green tea polyphenol fraction inhibited 12-O-tetradecanoyl-phorbol-13-acetate-induced tumor promotion in CD-1 mice previously initiated with 7,12-dimethylbenz[a]anthracene (DMBA). Oral administration of a green tea infusion as the sole source of liquid sustenance to SKH-1 mice inhibited ultraviolet B light (UVB)-induced sunburn lesions, UVB-induced initiation of skin tumors, UVB-induced formation of skin tumors in mice previously initiated with DMBA, and nitrosodiethylamine-induced forestomach and lung tumors in A/J mice. In addition to inhibiting UVB-induced formation of skin tumors in DMBA-initiated mice, oral administration of green tea markedly decreased tumor size.
279. Cancer Res. 1992 Jul 15;52(14):3875-9.
Inhibition of tobacco-specific nitrosamine-induced lung tumorigenesis in A/J mice by green tea and its major polyphenol as antioxidants.
Xu Y, Ho CT, Amin SG, Han C, Chung FL.
American Health Foundation, Valhalla, New York 10595.
In this study we examined the effects of green tea and its major components, (-)-epigallocatechin gallate (EGCG) and caffeine, on the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in A/J mice. We also studied the effects of green tea and EGCG on O6-methylguanine and 8-hydroxydeoxyguanosine (8-OH-dGuo) formation in lung tissues caused by NNK treatment. Mice were given 2% tea, 560 ppm EGCG, or 1120 ppm caffeine in drinking water for 13 weeks. During this time, NNK (11.65 mg/kg body weight) was administered by gavage three times weekly for 10 weeks from weeks 3 to 12. The bioassay was terminated 6 weeks after the last NNK treatment. Mice treated with NNK developed 22.5 lung adenomas per mouse, whereas NNK-treated mice that drank green tea or EGCG as drinking water developed only 12.2 (P less than 0.01) and 16.1 (P less than 0.05) tumors per mouse, respectively. Mice that drank green tea or caffeine solution showed lower body weight gains, although little difference in water and diet consumption was noted in these groups. While green tea and EGCG exerted little effect on the formation of O6-methylguanine, a critical DNA lesion in NNK lung tumorigenesis, both treatments suppressed the increase of 8-OH-dGuo levels in mouse lung DNA. The inhibition of 8-OH-dGuo formation in lung DNA by green tea and EGCG is consistent with their ability to inhibit lung tumorigenesis by NNK. Because 8-OH-dGuo is a DNA lesion caused by oxidative damage, these results suggest that the mechanism of inhibition by green tea and EGCG in NNK-induced lung tumorigenesis is due at least partly to their antioxidant properties.
280. Prev Med. 1992 May;21(3):351-60.
Tea components: antimutagenic and anticarcinogenic effects.
Mukhtar H, Wang ZY, Katiyar SK, Agarwal R.
Department of Dermatology, University Hospitals of Cleveland, Case Western Reserve University, Ohio.
BACKGROUND. Tea from the Camellia sinensis species of the Theaceae family is one of the most ancient and, next to water, the most widely consumed beverage in the world. Since tea contains several polyphenols and since several other naturally occurring dietary polyphenols have shown antimutagenic effects in bacteria and anticarcinogenic effects in animal bioassay systems, we studied whether polyphenols extracted from Chinese green tea (GTP) also possess antimutagenic and anticarcinogenic effects. RESULTS. GTP and its constituent epicatechin derivatives were found to interact with hepatic cytochrome P450 (P450) and inhibited the P450-dependent mixed-function oxidase enzymes in skin and liver. GTP and its epicatechin derivatives exhibited antimutagenic effects in several test systems. GTP showed substantial anti-skin-tumor-initiating and anti-skin-tumor-promoting activities when assessed in murine skin tumorigenesis bioassay systems. In these model systems polyaromatic hydrocarbons, benzo[a]pyrene (BP), 3-methyl-cholanthrene, 7,12-dimethylbenz[a]anthracene, and (+)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene (an ultimate carcinogenic metabolite of BP) were used as model skin carcinogens. The feeding of GTP in drinking water to SKH-1 hairless mice also afforded significant protection against ultraviolet-B-radiation-induced skin photocarcinogenesis. CONCLUSIONS. These data suggest that tea components possess antimutagenic and anticarcinogenic effects, and that they could protect humans against the risk of cancer by environmental agents.
281. Prev Med 1992 May;21(3):334-50
Green tea composition, consumption, and polyphenol chemistry.
Tea is grown in about 30 countries but is consumed worldwide, although at greatly varying levels. It is the most widely consumed beverage aside from water with a per capita worldwide consumption of approximately 0.12 liter per year. Tea is manufactured in three basic forms. green tea is prepared in such a way as to preclude the oxidation of green leaf polyphenols. During black tea production oxidation is promoted so that most of these substances are oxidized. Oolong tea is a partially oxidized product. Of the approximately 2.5 million metric tons of dried tea manufactured, only 20% is green tea and less than 2% is oolong tea. Green tea is consumed primarily in China, Japan, and a few countries in North Africa and the Middle East. Fresh tea leaf is unusually rich in the flavanol group of polyphenols known as catechins which may constitute up to 30% of the dry leaf weight. Other polyphenols include flavanols and their glycosides, and depsides such as chlorogenic acid, coumarylquinic acid, and one unique to tea, theogallin (3-galloylquinic acid). Caffeine is present at an average level of 3% along with very small amounts of the other common methylxanthines, theobromine and theophylline. The amino acid theanine (5-N-ethylglutamine) is also unique to tea. Tea accumulates aluminum and manganese. In addition to the normal complement of plant cell enzymes, tea leaf contains an active polyphenol oxidase which catalyzes the aerobic oxidation of the catechins when the leaf cell structure is disrupted during black tea manufacture. The various quinones produced by the enzymatic oxidations undergo condensation reactions which result in a series of compounds, including bisflavanols, theaflavins, epitheaflavic acids, and thearubigens, which impart the characteristic taste and color properties of black tea. Most of these compounds readily form complexes with caffeine. There is no tannic acid in tea. Thearubigens constitute the largest mass of the extractable matter in black tea but their composition is not well known. Proanthocyanidins make up part of the complex. Tea peroxidase may be involved in their generation. The catechin quinones also initiate the formation of many of the hundreds of volatile compounds found in the black tea aroma fraction. green tea composition is very similar to that of the fresh leaf except for a few enzymatically catalyzed changes which occur extremely rapidly following plucking. New volatile substances are produced during the drying stage. Oolong tea is intermediate in composition between green and black teas.
282. Kansenshogaku Zasshi 1992 May;66(5):606-11
[Antimicrobial and microbicidal activities of tea and catechins against Mycoplasma].
[Article in Japanese]
Chosa H, Toda M, Okubo S, Hara Y, Shimamura T
Department of Microbiology and Immunology, Showa University School of Medicine.
We examined tea extracts, (-) epigallocatechin gallate (EGCg) and theaflavin digallate (TF3) for their antimicrobial and microbicidal activities against Mycoplasma. green tea and black tea showed antimicrobial activities against M. pneumoniae. At a concentration of 0.2% green tea and black tea showed microbicidal activities against M. pneumoniae and M. orale but not against M. salivarium. Extracts of pu-erh tea showed a slight microbicidal activity against M. pneumoniae and M. orale. EGCg purified from green tea and TF3 from black tea markedly showed microbicidal activities against M. pneumoniae. M. orale and M. salivarium. These results suggest that tea and catechins can be used as prophylactic agents against Mycoplasma pneumoniae infection.
283. Kansenshogaku Zasshi 1992 May;66(5):599-605
[Protective activity of tea and catechins against Bordetella pertussis].
[Article in Japanese]
Horiuchi Y, Toda M, Okubo S, Hara Y, Shimamura T
Department of Microbiology and Immunology, Showa University School of Medicine.
We examined the bactericidal activity of tea and catechins against Bordetella pertussis. Green tea, black tea and coffee showed marked bactericidal activity at their concentrations in beverages, while pu-erh tea killed the bacteria in a moderate way. (-) epigallocatechin gallate (EGCg) and theaflavin digallate (TF3) showed also marked bactericidal activity. green tea and black tea also effectively blocked the adhesion of B. pertussis to HeLa and CHO cells, whereas ECGg and TF3 could not. EGCg and TF3 markedly inactivated leuco-lymphocytosis promoting activity of pertussis toxin. Black tea showed slight but significant inactivation of the activity, whereas green tea showed no inactivation. These results suggest that green tea, black tea, EGCg and TF3 might act as prophylactic agents against pertussis infection.
284. Cancer Res. 1992 Mar 1;52(5):1162-70.
Inhibitory effect of green tea in the drinking water on tumorigenesis by ultraviolet light and 12-O-tetradecanoylphorbol-13-acetate in the skin of SKH-1 mice.
Wang ZY, Huang MT, Ferraro T, Wong CQ, Lou YR, Reuhl K, Iatropoulos M, Yang CS, Conney AH.
Department of Chemical Biology and Pharmacognosy, College of Pharmacy, Rutgers, State University of New Jersey, Piscataway 08855.
Green tea was prepared by extracting 12.5 g of green tea leaves twice with 500 ml of boiling water, and the extracts were combined. This 1.25% green tea extract (1.25 g of tea leaves/100 ml of water) contained 4.69 mg of green tea extract solids per ml and was similar in composition to some green tea beverages consumed by humans. A 2.5% green tea extract (2.5 g of tea leaves/100 ml of water) was prepared similarly. Treatment of female SKH-1 mice with 180 mJ/cm2 of ultraviolet B light (UVB) once daily for 7 days resulted in red sunburn lesions of the skin. The intensity of red color and area of these lesions were inhibited in a dose-dependent fashion by the administration of 1.25 or 2.5% green tea extract as the sole source of drinking water before and during UVB treatment. Treatment of female SKH-1 mice with 180 mJ/cm2 of UVB once daily for 10 days followed 1 wk later by twice weekly application of 12-O-tetradecanoylphorbol-13-acetate for 25 wk resulted in the development of skin tumors. The formation of skin tumors was inhibited by administration of 1.25% green tea extract as the sole source of drinking water prior to and during the 10 days of UVB treatment and for 1 wk after UVB treatment. In additional experiments, female SKH-1 mice were treated with 200 nmol of 7,12-dimethylbenz(a)anthracene followed 3 wk later by irradiation with 180, 60, or 30 mJ/cm2 of UVB twice weekly for 30 wk. UVB-induced formation of skin tumors and increased spleen size were inhibited by administration of 1.25% green tea extract as the sole source of drinking water prior to and during the 30 wk of UVB treatment. In these experiments, treatment of the animals with the green tea extract not only decreased the number of skin tumors but also decreased substantially the size of the tumors. In additional studies, SKH-1 mice were initiated by topical application of 200 nmol of 7,12-dimethylbenz(a)anthracene followed by twice weekly application of 12-O-tetradecanoylphorbol-13-acetate for 25 wk. Administration of 1.25% green tea extract as the sole source of drinking water during promotion with 12-O-tetradecanoylphorbol-13-acetate reduced the number and incidence of skin tumors.
285. Teratog Carcinog Mutagen 1992;12(2):79-95
Strategy of research for cancer--chemoprevention.
Ito N, Imaida K
First Department of Pathology, Nagoya City University Medical School, Japan.
It has been reported that environmental chemicals are important factors in terms of both development and prevention of human cancer. For the latter, detection of early stages is an essential first step followed by clinical trials for surveying populations at risk. Thus a great deal of attention has been focused on these areas. However, investigations of possibilities for active prevention of cancer development itself form another major project. Chemoprevention of carcinogenesis, which means prevention of carcinogenesis by exogenous chemical compounds, has been investigated extensively in a variety of organs in animal models. Usually attention is concentrated on only one organ. However, antioxidants, such as BHA, exert very different effects on different organs, suggesting the necessity of whole body approaches to the question of chemoprevention. Furthermore, the mechanisms of chemoprevention, including the step of carcinogenesis, i.e., initiation, promotion, progression or whole carcinogenesis steps, in which exogenous compounds exert their protective effects, should be considered. A medium-term bioassay system and a multi-organ carcinogenesis system, which can be used for investigation of potential for cancer chemoprevention, have been developed in our laboratory. Dose dependent inhibitory effects were established for both BHA and alpha-tocopherol in the medium-term bioassay system, and inhibition of small intestinal carcinogenesis by catechins in green tea has also been investigated in our multi-organ carcinogenesis protocol. It is extremely important for prevention of human cancer that we find new candidates for chemopreventive agents using animal studies. This paper reviews published reports on chemoprevention, taking into account effective stages, and proposes suitable experimental animal models for future investigations in this increasingly important area.
286. Jpn J Med Sci Biol 1991 Aug;44(4):181-6 Inhibition of rotavirus and enterovirus infections by tea extracts. Mukoyama A, Ushijima H, Nishimura S, Koike H, Toda M, Hara Y, Shimamura T. Department of Enteroviruses, National Institute of Health, Tokyo, Japan.
Epigallocatechin gallate from green tea and theaflavin digallate from black tea inhibited infections of cultured rhesus monkey kidney MA 104 cells with rotaviruses and enteroviruses. Their antiviral effects were maximally induced when directly added to virus, and their pre- and post-treatment of the cells produced much weak antiviral activity. Antiviral activity of the extracts therefore seems to be attributable to interference with virus adsorption.
287. Caries Res 1991;25(6):438-43
Anticaries effects of polyphenolic compounds from Japanese green tea.
Otake S, Makimura M, Kuroki T, Nishihara Y, Hirasawa M
Department of Clinical Pathology, Nihon University School of Dentistry, Matsudo, Japan.
The dental caries inhibiting effect of the extract from Japanese green tea, one of the most popular drinks in Japan, was studied both in vitro and in vivo. The crude tea polyphenolic compounds (designated Sunphenon) from the leaf of Camellia sinensis were found to effectively inhibit the attachment of Streptococcus mutans strain JC-2 (serotype c) to saliva-coated hydroxyapatide discs. Sunphenon was also inhibitory to water-insoluble glucan formation from sucrose by crude glucosyltransferase of S. mutans JC-2 (c). Among the tea catechins tested, (-)-epigallocatechin gallate and (-)-epicatechin gallate showed the most potent inhibition of the glucosyltransferase activity. Finally, significantly lower caries scores were observed in specific pathogen free rats infected with S. mutans JC-2 (c) and fed a cariogenic diet and/or drinking water containing 0.05% Sunphenon as compared with control rats not receiving polyphenolic compounds.
288. Chem Pharm Bull (Tokyo) 1990 Mar;38(3):790-3
Platelet aggregation inhibitors in hot water extract of green tea.
Sagesaka-Mitane Y, Miwa M, Okada S
Ito-en Central Research Institute, Shizuoka, Japan.
The effect of hot water extract of green tea on the collagen-induced aggregation of washed rabbit platelets was examined. The extract lowered submaximal aggregation and prolonged the lag time in a dose-dependent manner. After fractionation of the extract, it was revealed that the tea catechins (tannins) are active principles for inhibition and that ester-type catechins are more effective than free-type catechins. One of the ester type catechins, epigallocatechin gallate (EGCG), suppressed the collagen-induced platelet aggregation completely at the concentration of 0.2 mg/ml (= 0.45 mM). Comparing IC50 values of EGCG and aspirin it was found that the potency of EGCG is comparable to that of aspirin. Thrombin- and platelet activating factor (PAF)-induced aggregation was also inhibited by EGCG. The elevation of cyclic adenosine 3',5'-monophosphate (cAMP) level was not observed in EGCG treated platelets.
289. Chem Pharm Bull (Tokyo). 1990 Mar;38(3):717-20.
Effect of tea polyphenols on glucan synthesis by glucosyltransferase from Streptococcus mutans.
Hattori M, Kusumoto IT, Namba T, Ishigami T, Hara Y.
Research Institute for Wakan-Yaku, Toyama Medical and Pharmaceutical University, Japan.
In the course of our studies on the development of anti-plaque agents for prevention of dental caries, we investigated effects of some of tea preparations and their individual components on the glucan synthesis catalyzed by glucosyltransferase (GTF) from Streptococcus mutans. Extracts of green tea and black tea, and polyphenol mixtures showed appreciable inhibition in the synthesis of insoluble glucan. Among the components isolated from tea infusions, theaflavin and its mono- and digallates had potent inhibitory activities at concentrations of 1-10 mM against GTF. (+)-Catechin, (-)-epicatechin and their enantiomers had moderate inhibitory activities at these concentrations, while galloyl esters of (-)-epicatechin, (-)-epigallocatechin and (-)-gallocatechin had increased inhibitory activities.
290. Carcinogenesis 1989 Jun;10(6):1003-8
Prevention of cytotoxicity and inhibition of intercellular communication by antioxidant catechins isolated from Chinese green tea.
Ruch RJ, Cheng SJ, Klaunig JE
Department of Pathology, Medical College of Ohio, Toledo 43699.
An antioxidant fraction of Chinese green tea (green tea antioxidant; GTA), containing several catechins, has been previously shown to inhibit 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tumor promotion in mouse skin. In the present study, GTA was shown to have antioxidative activity toward hydrogen peroxide (H2O2) and the superoxide radical (O2-). GTA also prevented oxygen radical and H2O2-induced cytotoxicity and inhibition of intercellular communication in cultured B6C3F1 mouse hepatocytes and human keratinocytes (NHEK cells). GTA (0.05-50 micrograms/ml) prevented the killing of hepatocytes (measured by lactate dehydrogenase release) by paraquat (1-10 mM) and glucose oxidase (0.8-40 micrograms/ml) in a concentration-dependent fashion. GTA (50 micrograms/ml) also prevented the inhibition of hepatocyte intercellular communication by paraquat (5 mM), glucose oxidase (0.8 micrograms/ml), and phenobarbital (500 micrograms/ml). In addition, GTA (50 micrograms/ml) prevented the inhibition of intercellular communication in human keratinocytes by TPA (100 ng/ml). Cytotoxicity and inhibition of intercellular communication, two possible mechanisms by which tumor promoters may produce their promoting effects were therefore prevented by GTA. The inhibition of these two effects of pro-oxidant compounds may suggest a mechanism by which GTA inhibits tumor promotion in vivo.
291. Mutat Res 1989 Jan;210(1):1-8
Crude tea extracts decrease the mutagenic activity of N-methyl-N'-nitro-N-nitrosoguanidine in vitro and in intragastric tract of rats.
Jain AK, Shimoi K, Nakamura Y, Kada T, Hara Y, Tomita I
Laboratory of Health Science, School of Pharmaceutical Sciences, University of Shizuoka, Japan.
The effects of tea extracts and their ingredients, catechins and L-ascorbic acid (AsA), on the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were examined in vitro and in the stomachs of rats using E. coli WP2 and S. typhimurium TA100. The extracts of green tea and black tea leaves decreased the mutagenic activity of MNNG to E. coli WP2 in vitro in a desmutagenic manner. Catechins such as (-)-epigallocatechin from green tea leaves and the low-molecular-weight tannin fraction isolated from black tea extract with HP-20 resin also exhibited inhibitory effects against the mutagenic activity of MNNG. A desmutagenic effect of AsA on MNNG-induced mutagenicity was observed depending on the dose, though it was complicated. The effects were also demonstrated in the stomachs of rats by assaying the bacterial mutagenic in vitro; the tea extracts previously given orally to rats reduced the mutagenic activity of MNNG remarkably, though simultaneous administration showed less effect. The effectiveness of tea extracts for the decrease of MNNG-induced mutagenesis in vitro and in vivo suggests that the habitual drinking of tea may reduce the tumor-initiating potency of MNNG-type nitrosoureido compounds if they are formed in the stomach.
292. J Nutr Sci Vitaminol (Tokyo) 1986 Dec;32(6):613-22
Effect of green tea catechins on plasma cholesterol level in cholesterol-fed rats.
Muramatsu K, Fukuyo M, Hara Y
Effects of tea catechins (tannins) on lipid metabolism were studied in male weanling rats fed a 25% casein diet containing 15% lard and 1% cholesterol for 28 days. Crude tea catechins prepared from green tea powder were supplemented at a 1% and 2% of the lard-cholesterol diet. The addition of 2% tea catechins slightly depressed growth but at the 1% level was without effect. Tea catechins decreased plasma total cholesterol, cholesterol ester, total cholesterol--HDL-cholesterol (VIDL-+LDL-cholesterol) and atherogenic index (VLDL-+LDL-cholesterol/HDL-cholesterol). Hematocrit and plasma glucose were not altered by the addition of tea catechins. The liver weight, liver total lipids and cholesterol concentrations in rats fed the lard-cholesterol diet increased more than in the control rats, but the addition of tea catechins to the lard-cholesterol diet decreased those parameters. Tea catechin supplementation increased fecal excretion of total lipids and cholesterol. The results demonstrate that tea catechins exert a hypocholesterolemic effect in cholesterol-fed rats.