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PubMed2001

Green tea extracts decrease carcinogen-induced mammary tumor burden in rats and rate of breast cancer cell proliferation in culture.

Epidemiological evidence suggests tea (Camellia sinensis L.) has chemopreventive effects against various tumors. Green tea contains many polyphenols, including epigallocatechin-3 gallate (EGCG), which possess anti-oxidant qualities. Reduction of chemically induced mammary gland carcinogenesis by green tea in a carcinogen-induced rat model has been suggested previously, but the results reported were not statistically significant. Here we have tested the effects of green tea on mammary tumorigenesis using the 7,12-dimethylbenz(a)anthracene (DMBA) Sprague-Dawley (S-D) rat model. We report that green tea significantly increased mean latency to first tumor, and reduced tumor burden and number of invasive tumors per tumor-bearing animal; although, it did not affect tumor number in the female rats. Furthermore, we show that proliferation and/or viability of cultured Hs578T and MDA-MB-231 estrogen receptor-negative breast cancer cell lines was reduced by EGCG treatment. Similar negative effects on proliferation were observed with the DMBA-transformed D3-1 cell line. Growth inhibition of Hs578T cells correlated with induction of p27(Kip1) cyclin-dependent kinase inhibitor (CKI) expression. Hs578T cells expressing elevated levels of p27(Kip1) protein due to stable ectopic expression displayed increased G1 arrest. Thus, green tea had significant chemopreventive effects on carcinogen-induced mammary tumorigenesis in female S-D rats. In culture, inhibition of human breast cancer cell proliferation by EGCG was mediated in part via induction of the p27(Kip1) CKI.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2005

Sensory evaluation of the synergism among odorants present in concentrations below their odor threshold in a Chinese jasmine green tea infusion.

The mechanism for the contribution of subthreshold aroma constituents to the overall jasmine tea odor impression was studied on the basis of a sensory evaluation. Binary model aqueous solutions containing the authentic odorants of a jasmine tea infusion, (E)-2-hexenyl hexanoate (I), (Z)-3-hexenol (II), and indole (III), were each prepared in a concentration below the odor threshold. Each solution had no aroma, but when 4-hexanolide replaced only 5% of each odorant, the odor intensity of each model solution was significantly strengthened. An astringent note and heavy note were recognized for each solution as the commonly perceived characteristics from the sensory evaluation. The concentration of 4-hexanolide added was also at the subthreshold level. The results suggest mutual interaction between odorants I, II, or III and 4-hexanolide. The effect on the overall odor sensation of a jasmine tea infusion by adding 4-hexanolide at a concentration below its odor threshold was also studied. In this case, the intensity of both the sweet and astringent notes was significantly strengthened in comparison with the odor impression of the original jasmine tea infusion. This phenomenon is considered to have been a synergistic effect between subthreshold odor compounds in the jasmine tea infusion. The results of this study clarify for the first time that the subthreshold aroma constituents play an important role in the characteristic flavor of a jasmine tea infusion.

Adult↗
PubMed2006

Anti-obesity effects of green tea: from bedside to bench.

During the last decade, the traditional notion that green tea consumption benefits health has received significant scientific attention and, particularly, the areas of cardiovascular disease and cancer were subject to numerous studies. Due to the ever-growing obesity pandemic, the anti-obesity effects of green tea are being increasingly investigated in cell, animal, and human studies. Green tea, green tea catechins, and epigallocatechin gallate (EGCG) have been demonstrated in cell culture and animal models of obesity to reduce adipocyte differentiation and proliferation, lipogenesis, fat mass, body weight, fat absorption, plasma levels of triglycerides, free fatty acids, cholesterol, glucose, insulin and leptin, as well as to increase beta-oxidation and thermogenesis. Adipose tissue, liver, intestine, and skeletal muscle are target organs of green tea, mediating its anti-obesity effects. Studies conducted with human subjects report reduced body weight and body fat, as well as increased fat oxidation and thermogenesis and thereby confirm findings in cell culture systems and animal models of obesity. There is still a need for well-designed and controlled clinical studies to validate the existing and encouraging human studies. Since EGCG is regarded as the most active component of green tea, its specific effects on obesity should also be investigated in human trials.

Absorption↗
PubMed2002

Inhibition of tumour growth and inflammation by consumption of tea.

The antitumour effect of tea was evaluated in the 3-methylcholanthrene (3-MC) induced solid tumour model in mice. Both black and green tea inhibited tumour growth and prevented metastasis. Histopathological study showed that tea treatment was able to reduce malignancy. Superoxide dismutase (SOD), a free radical scavenger, was found to be significantly increased in the serum of mice administered tea. Moreover, tea extracts were able to reduce the level of thiobarbituric acid reactive substance (TBARS) in the sera of mice. Tea extracts (both black and green) also showed antiinflammatory activity in the carrageenan-induced paw oedema model in the rat.

Animals↗
PubMed2001

The effects of phenolic components of tea on the production of pro- and anti-inflammatory cytokines by human leukocytes in vitro.

Epidemiological evidence suggests protective effects of dietary flavonoids against cardiovascular disease. Tea provides a major source of dietary flavonoids in many countries and its polyphenolic components have well-recognised antioxidant properties. However, scavenging of free radicals may not be the sole mechanism by which tea-derived polyphenols exert their protective effects. This study investigates the effects of four major tea-derived catechins and a black tea extract on the production of pro- and anti-inflammatory cytokines by human leukocytes in vitro. Epicatechin gallate, epigallocatechin and epigallocatechin gallate decreased the production of interleukin 1beta and enhanced the production of interleukin 10, but had no effect on the production of interleukin 6 or tumour necrosis factor-alpha. Although these effects suggest anti-inflammatory properties of the tea-derived catechins, they were observed at concentrations which were unlikely to be achievable in plasma in vivo and are therefore unlikely to contribute to the protective effects of tea-derived flavonoids in inflammatory diseases.

Anti-Inflammatory Agents↗
PubMed1993

Determination of flavone C-glycosides in tea.

An HPLC method for the determination of flavone C-glycosides (FCG) from black tea has been developed. Sample clean-up was accomplished by means of polyamide column chromatography, followed by enzyme hydrolysis of interfering compounds such was flavonol glycosides and a second polyamide column chromatographic step. Using HPLC with gradient elution and photodiode array detection eight FCG were separated. Seven FCG were isolated by means of preparative HPLC. Identification was carried out using co-chromatography, FAB(Fast Atom Bombardment)-mass spectrometry and various nuclear magnetic resonance techniques. Apigenin 6-C-glucosyl-8-arabinoside (schaftoside) and apigenin 6-C-arabinosyl-8-C-glucoside (isoschaftoside) as well as luteolin 8-C-glucoside (orientin) and luteolin 6-C-glucoside (isoorientin) have been detected in tea for the first time. Three of the other compounds have been identified as apigenin 8-C-glucoside (vitexin), apigenin 6-C-glucoside (isovitexin) and apigenin 6,8-di-C-glucoside (vicenin-2). Their occurrence in tea has been previously reported. From its UV spectrum another compound was concluded to be an apigenin glycoside. The FCG were quantified in a variety of teas of different origins (16 black, two green and one oolong). The total amounts of the FCG were 0.48-2.69 g/kg dry weight. The FCG pattern of teas of different origins were similar to each other and no origin-dependent characteristics have yet been observed. Small amounts of FCG (1.2-2.2 mg/kg) were detected in hydrolysates of high relative molecular mass fractions (Mr > 5000) of a black tea liquor.

Apigenin↗
PubMed1999

Mood and drinking: a naturalistic diary study of alcohol, coffee and tea.

Understanding the pattern of associations between mood and consumption of alcohol, coffee and tea may provide information about the factors governing beverage drinking. The associations between mood and the consumption of alcohol, coffee and tea during everyday life were assessed. A naturalistic study was carried out with 18 male and 31 female volunteers from two working groups (psychiatric nursing and school teaching). Participants completed daily records of drink consumption, together with ratings of anxious and positive moods for 8 weeks. Potential moderators of associations were self-reported drinking to cope, high perceived job demands and social support at work. Day-by-day associations were analysed using Spearman correlations. There were substantial individual-differences in associations between mood and daily alcohol, coffee and tea consumption. Overall, alcohol intake was associated with high positive and low anxious mood. This effect was not present among participants with high drinking to cope ratings. Coffee and tea drinking were not consistently related to mood across the entire sample. However, job demands influenced the association between coffee consumption and anxious mood in men, and those who experienced high job demands drank more coffee on days on which they felt anxious. In contrast, women but not men who enjoyed high social support at work felt more relaxed on days on which they drank more tea. These results indicate that people vary widely in the extent to which mood is related to the drinking of alcohol, coffee and tea. The strength of associations is influenced by gender, motivational factors, and by stress and coping resources.

Adaptation, Psychological↗
PubMed1999

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.

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.

Adult↗
PubMed2005

Daily tea drinking is associated with a low level of depressive symptoms in the Finnish general population.

Tea drinking has been suggested to be beneficial in neurodegenerative diseases where depressive mood is a common symptom. Nevertheless, it is not known whether there are any associations between tea drinking and depression in general populations. In this study we investigated these associations in a sample of the Finnish general population (n = 2011) using a postal questionnaire and the Beck Depression Inventory (BDI). Those who reported drinking tea daily were less depressed than the others. They had a lower mean BDI score and also a lower prevalence of depression. None of those whose daily tea intake was five cups or more had depression. Several potential confounding factors were included in the final sex- and age-adjusted multivariate logistic regression model which suggested that those who drink tea daily may have a significantly reduced risk of being depressed (adjusted odds ratio 0.47, 95% confidence interval 0.27-0.83). In conclusion, an inverse relationship between daily tea drinking and the risk of being depressed was found in a relatively large general population sample. Nevertheless, the underlying mechanisms are unresolved and further studies are needed.

Adult↗
PubMed2005

Antimutagenic properties of green tea.

In this work biological effects of two common kinds of green tea (Chinese Gunpowder and Japanese Sencha) were analyzed using three independent tests of antimutagenicity: 1) the Ames test with Salmonella typhimurium TA98, 2) cytogenetic analysis of peripheral blood lymphocytes (CAPL), and 3) test with Saccharomyces cerevisiae D7. Tea extracts were allowed to be antimutagenic based on their ability to inhibit the mutagenic effect of standard mutagens. Amounts of (-)catechin and (-)catechin gallate in tea extracts were determined by high performance liquid chromatography on reversed phase (RP-HPLC). Antioxidant capacity was found using total radical-trapping antioxidant parameter (TRAP) method. Extracts from Gunpowder and Sencha exhibited high antimutagenic activity in the Ames test (24.7+/-3.7% and 34.1+/-2, 1% of inhibition without metabolic activation; 74.9+/-1.7% and 62.7+/-4.3% of inhibition with metabolic activation, respectively) as well as in S. cerevisiae D7 test (Gunpowder: 62.7+/-5.7% of Trp convertants inhibition and 52.6+/-5.3% of Ilv revertants inhibition; Sencha: 45.6+/-4.2% of Trp convertants inhibition, 50.0+/-4.8% of Ilv revertants inhibition). In the CAPL method reduced number of abberant cells as well as decreased number of chromosome breaks was observed using both green tea extracts. Antioxidant capacity and antimutagenicity of green tea extracts was higher than activity of tea catechins and flavonoids.

Antimutagenic Agents↗
PubMed1993

Gastro-intestinal availability of aluminium from tea.

The in vitro speciation of aluminium (Al) in black tea infusion (pH 4.8) was assessed using 3000, 10,000 and 30,000 Da cut-off ultrafilters, and the effect of adding human gastric juice (pH 2.3) and then raising the pH to 6.5 were also studied. 78% Al in the tea infusion passed through the 3000-Da ultrafilter; this percentage increased to more than 90% with the addition of gastric juice at pH 2.3, but then reduced to approximately 5% when the incubate was adjusted to pH 6.5. The breakdown of tea-derived polyphenols to low molecular weight phenols in vivo was measured using high-resolution 1H nuclear magnetic resonance spectroscopic analysis of ileostomy effluent, but there was no evidence of low molecular weight breakdown products from the polyphenols of ingested tea in this effluent. These results suggest that only a small proportion of Al in tea is potentially available for absorption throughout the small bowel. It may be misleading to estimate systemic Al absorption from tea drinking simply from total urinary aluminium excretion as has been done previously.

Aluminum↗
PubMed1995

Preventive effects of green tea against liver oxidative DNA damage and hepatotoxicity in rats treated with 2-nitropropane.

Male rats were given 2% green tea as their drinking water for 2 wk before a single ip injection of the carcinogen 2-nitropropane (2NP) (100 mg/kg body weight) and liver nuclear 8-hydroxydeoxyguanosine (8-OHdG) levels and hepatotoxicity parameters were determined 6 or 15 hr thereafter. The increase of 8-OHdG adducts in liver nuclear DNA caused by 2NP was depressed 50% at both time points with the green tea pretreatment. The time-dependent elevations of serum aminotransferases and lactate dehydrogenase values by 2NP were also effectively prevented. However, green tea had no obvious effects on the falls in serum lipid peroxide and triglyceride levels associated with carcinogen exposure. Increases of hepatic lipid peroxide levels with 2NP were depressed 100 and 30%, at 6 and 15 hr, respectively, by green tea and the decrease in hepatic glycogen content at 6 hr was clearly alleviated. Histopathological examination revealed effective protection against induction of hepatic degenerative changes by 2NP at 15 hr. Drinking crude catechin extract solution with the same concentration of (-)epigallocatechin gallate as green tea provided protection at 6 hr, but with only half the effectiveness. These findings demonstrate that green tea can effectively block oxidative DNA damage to the liver as well as hepatotoxicity in rats treated with 2NP.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1995

Effect of green tea rich in gamma-aminobutyric acid on blood pressure of Dahl salt-sensitive rats.

gamma-Aminobutyric acid (GABA) is known to be involved in the regulation of blood pressure by modulating the neurotransmitter release in the central and peripheral sympathetic nervous systems. This study investigated the antihypertensive effect of green tea rich in GABA (GABA-rich tea) in young and old Dahl salt-sensitive (S) rats. GABA-rich tea was made by fermenting fresh green tea leaves under nitrogen gas. In experiment 1, 21 11-month-old rats, fed a 4% NaCl diet for 3 weeks, were given water (group W), an ordinary tea solution (group T), or a GABA-rich tea solution (group G) for 4 weeks. The average GABA intake was 4.0 mg/rat per day. After 4 weeks of the treatment, blood pressure was significantly decreased in group G (176 +/- 4; P < .01) compared with group W (207 +/- 9) or group T (193 +/- 5 mm Hg). Plasma GABA levels were more elevated in group G (111 +/- 54) than in group W (not detectable) or group T (14 +/- 8 ng/mL; P < .01 v G). In experiment 2, 21 5-week-old rats, fed a 4% NaCl diet, were divided into groups W, T, and G. The average GABA intake was 1.8 mg/rat per day. Body weight or chow and beverage consumption did not differ significantly among the three groups. After 4 weeks of the treatment, although blood pressure was comparable in groups W and T (165 +/- 3 v 164 +/- 5 mm Hg, mean +/- SE), it was significantly lower in group G (142 +/- 3 mm Hg) than in the other groups (P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Green tea supplementation in rats of different ages mitigates ethanol-induced changes in brain antioxidant abilities.

Oxidative stress induced by chronic ethanol consumption, particularly in aging subjects, has been implicated in the pathophysiology of many neurodegenerative diseases. Antioxidants with polyphenol structures, such as those contained in green tea, given alone for 5 weeks in liquid Lieber de Carli diet followed by administration with ethanol for 4 weeks with ethanol have been investigated as potential therapeutic antioxidant agents in the brain in rats of three ages (2, 12, and 24 months). Ethanol consumption caused age-dependent decreases in brain superoxide dismutase, glutathione peroxidase, glutathione reductase, and catalase activities. In addition, ethanol consumption caused age-dependent decreases in the levels of GSH, selenium, vitamins, E, A and C, and beta-carotene and increases in the levels of oxidized glutathione (GSSG). Changes in the brain's antioxidative ability were accompanied by enhanced oxidative modification of lipids (increases in lipid hydroperoxides, malondialdehyde, and 4-hydroxynonenal levels) and proteins (increases in carbonyl groups and bistyrosine). Reduced risk of oxidative stress and protection of the central nervous system, particularly in young and adult rats, after green tea supplementation were observed. Green tea partially prevented changes in antioxidant enzymatic as well as nonenzymatic parameters induced by ethanol and enhanced by aging. Administration of green tea significantly protects lipids and proteins against oxidative modifications in the brain tissue of young and adult rats. The beneficial effect of green tea can result from the inhibition of free radical chain reactions generated during ethanol-induced oxidative stress and/or from green tea-induced increases in antioxidative abilities made possible by increases in the activity/concentration of endogenous antioxidants.

Aging↗
PubMed2004

Green tea catechins inhibit neointimal hyperplasia in a rat carotid arterial injury model by TIMP-2 overexpression.

OBJECTIVE: Although it has been demonstrated that the antioxidant properties of tea catechins reduce atherosclerotic lesions in various animal models of hyperlipidemia, it is not yet clear whether these catechins prevent hyperlipidemia-independent arterial remodeling induced by balloon angioplasty. We evaluated the influence of the administration of the tea extract on vascular remodeling in a rat carotid artery balloon-injury model. METHODS AND RESULTS: Male Wistar rats were supplied drinking water with or without green tea extract (1 mg/ml) supplement. Administration of the tea extract reduced the area of the intima (30%) and the ratio of the intimal area to the medial area (36.2%) in injured arteries compared with those of control rats at 14 days after the injury. Real-time RT-PCR, Western blot, and gelatin zymography revealed a significant increase in tissue inhibitor of matrix metalloproteinase (MMP)-2 (TIMP-2) expression as well as a significant reduction of gelatinolytic net activity and activated MMP-2 levels in the injured arteries as a result of the administration of the tea extract compared with those of control group. Similarly, epigallocatechin-3-gallate, a major constituent of green tea catechins, significantly upregulated TIMP-2 expression in cultured smooth muscle cells. Immunohistochemical analysis showed that the increase of TIMP-2 protein occurred preferentially in the developing neointima. CONCLUSION: These results indicate that catechins inhibit intimal hyperplasia in a rat balloon-injury model through the upregulation of TIMP-2 expression to modulate MMP activity.

Angioplasty, Balloon↗
PubMed2005

Analytical separation of tea catechins and food-related polyphenols by high-speed counter-current chromatography.

High-speed counter-current chromatography (HSCCC) using the type-J coil planet centrifuge was applied to compositional analysis of tea catechins and separation of other food-related polyphenols. The HSCCC separation of nine different standard compounds and those from extracts of commercial tea leaves was performed with a two-phase solvent system composed of tert-butyl methyl ether-acetonitrile-0.1% aqueous trifluoroacetic acid (TFA) (2:2:3, v/v/v) by eluting the upper organic phase at a flow rate of 2 ml/min. The main compounds in the extract of non-fermented green tea were found to be monomeric catechins, their galloylated esters and caffeine. In addition to these compounds, oxidized pigments, such as hydrophobic theaflavins (TFs) and polar thearubigins (TRs) were also separated and detected from the extracts of semi-fermented oolong tea and fermented black tea. Furthermore, several food-related polyphenols, such as condensed catechin oligomers (procyanidins), phenolic acids and flavonol glycosides were clearly separated under the same HSCCC condition. These separation profiles of HSCCC provide useful information about the hydrophobic diversity of these bioactive polyphenols present in various types of teas and food products.

Biflavonoids↗
PubMed2004

Oolong tea increases plasma adiponectin levels and low-density lipoprotein particle size in patients with coronary artery disease.

BACKGROUND: Oolong tea has been studied for its effect on cardiovascular disease and obesity. Plasma adiponectin levels are reduced in obesity, in patients with type 2 diabetes mellitus and in coronary artery disease (CAD). OBJECTIVE: To investigate prospectively, whether intake of Oolong tea influences plasma adiponectin levels, low-density lipoprotein (LDL) particle size, total cholesterol, high-density lipoprotein (HDL) cholesterol, LDL cholesterol, serum triglyceride and plasma glucose levels in patients with CAD. METHODS: Twenty two patients in our study consumed Oolong tea (1000 ml) or water for 1 month in our randomized cross-over study design. RESULTS: There was a significant difference in plasma adiponectin levels before and after 1 month intake of Oolong tea (6.26 +/- 3.26 microg/ml versus 6.88 +/- 3.28 microg/ml, P < 0.05), and in plasma level LDL particle size (25.02+/-0.67 nm versus 25.31+/-0.60 nm, P < 0.01). The water-consuming control group showed no changes (6.28+/-3.28 microg/ml versus 6.23+/-3.21 microg/ml) in adiponectin levels or LDL particle sizes (25.03+/-0.70 nm versus 25.02+/-0.72 nm). We also observed a significant difference in hemoglobin A1c levels (7.23 +/- 4.45% versus 6.99 +/- 4.30%, P < 0.05) before and after intake of Oolong tea. CONCLUSION: Oolong tea may have beneficial effects on the progression of atherosclerosis in patients with CAD.

Adiponectin↗
PubMed2004

Black tea polyphenol theaflavins inhibit aromatase activity and attenuate tamoxifen resistance in HER2/neu-transfected human breast cancer cells through tyrosine kinase suppression.

The aromatase enzyme, which converts androstenedione to oestrone, regulates the availability of oestrogen to support the growth of hormone-dependent breast tumours. In this study, we investigated the inhibitory effects of black tea polyphenols on aromatase activities. We found that black tea polyphenols, TF-1, TF-2 and TF-3, significantly inhibited rat ovarian and human placental aromatase activities. In addition, using an in vivo model, these black tea polyphenols also inhibited the proliferation induced by 100 nM dehydroepiandrosterone (DHEA) in MCF-7 cells. Transfection of HER2/neu in MCF-7 breast cancer cells appeared to be associated with an increased resistance of the cells to hormonal therapy. Interestingly, unlike the selective oestrogen receptor modulator (SERM) tamoxifen, black tea polyphenols had antiproliferation effects in breast cancer cells with hormonal resistance. The inhibitory effect of black tea polyphenols on hormone-resistant breast cancer cells suppressed the basal receptor tyrosine phosphorylation in HER2/neu-overexpressing MCF-7 cells. These findings suggest the use of black tea polyphenols may be beneficial in the chemoprevention of hormone-dependent breast tumours and represent a possible remedy to overcome hormonal resistance of hormone-independent breast tumours.

Animals↗