Research Database

Author: Anais Gondoin and Dominic Grussu and Derek Stewart and Gordon J. McDougall

Green, white and black teas were assayed for inhibition of pancreatic lipase activity in vitro. White tea proved to be more effective than green tea with black tea showing little inhibition even at 200 μg GAE/ml. The EC50 values for inhibition were 22 μg/ml for white tea and 35 μg/ml for green tea; both easily achievable from normal infusions of tea. Liquid chromatography-mass spectroscopy analysis showed that white and green teas had essentially equal amounts of flavan-3-ols but green tea had higher levels of flavonols. White tea had higher levels of 5-galloyl quinic acid, digalloyl glucose, trigalloyl glucose and the tannin, strictinin. After chromatography on Sephadex LH-20, the main inhibitory fraction was enriched in strictinin and fractions enriched in other components were ineffective. This suggests that strictinin content may be crucial for inhibition of pancreatic lipase. However, the possibility of synergies between the polyphenols cannot be disregarded.

 

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Author: Amar K. Chandra and Neela De

Catechins are flavonoids found in abundance in green tea, have elicited high interest due to their beneficial effects on health. Though flavonoids have been reported to have an antithyroid effect and also to be goitrogenic there have been no reports about the effect of green tea on rat thyroid. The present study was designed to examine whether high doses of green tea has any harmful effect on thyroid physiology. For this purpose green tea extract was administered orally to male albino rats for 30 days at doses of 1.25 g%, 2.5 g% and 5.0 g%, respectively. Similarly, pure catechin was administered at doses of 25, 50 and 100 mg/kg body weight which is equivalent to above doses of green tea extract. Lower body weight gain associated with marked hypertrophy and/or hyperplasia of the follicles was noted in the high dose of green tea and catechin treated groups. Decreased activity of thyroid peroxidase and 5′-deiodinase I and substantially elevated thyroidal Na,K + ATPase activity have been observed. Moreover, serum T3 and T4 levels were found to reduce followed by significant elevation of serum TSH. Taken together, these results suggest that catechin present in green tea extract might behave as antithyroid agent and possibly the consumption of green tea at high dose could alter thyroid function adversely.

 

 

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Author: Qi Dai and Xiao-Ou Shu and Honglan Li and Gong Yang and Martha J. Shrubsole and Hui Cai and Butian Ji and Wanqing Wen and Adrian Franke and Yu-Tang Gao and Wei Zheng

Background Studies have found that tea polyphenols inhibit aromatase. Because of the substantial difference in levels of estrogens between premenopausal and postmenopausal women, the relationship between tea consumption and breast cancer risk may depend on menopausal status. Methods We examined this hypothesis in the Shanghai Women's Health Study, a population-based cohort study of 74,942 Chinese women. Results We found a time-dependent interaction between green tea consumption and age of breast cancer onset (p for interaction, 0.03). In comparison with non-tea drinkers, women who started tea-drinking at 25 years of age or younger had a hazard ratio (HR) of 0.69 (95% confidence interval [CI]: 0.41–1.17) to develop premenopausal breast cancer. On the other hand, compared with non-tea drinkers, women who started tea drinking at 25 years of age or younger had an increased risk of postmenopausal breast cancer with an HR of 1.61 (95% CI: 1.18–2.20). Additional analyses suggest regularly drinking green tea may delay the onset of breast cancer. Conclusions Further studies are needed to confirm our findings.

 

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Author: Qiong Li and Haifeng Zhao and Ming Zhao and Zhaofeng Zhang and Yong Li

As the organism ages, production of reactive oxygen species (ROS) increases while antioxidants defense capability declines, leading to oxidative stress in critical cellular components, which further enhances ROS production. In the brain, this vicious cycle is more severe as brain is particularly vulnerable to oxidative damage. In our study, 14-month-old female C57BL/6J mice were orally administered 0.05% green tea catechins (GTC, w/v) in drinking water for 6 months. We found that GTC supplementation prevented the decrease in total superoxide dismutase and glutathione peroxidase activities in serum as well as reduced the thiobarbituric acid reactive substances and protein carbonyl contents in the hippocampus of aged mice. The activation of transcriptional factor nuclear factor-kappa B and lipofuscin formation in pyramidal cells of hippocampal CA1 region, which are all related to oxidative stress, was also reduced after GTC treatment. We also found that long-term GTC treatment prevented age-related reductions of two representative post-synaptic proteins post-synaptic density 95 and N-methyl-d-aspartate receptor 1 in the hippocampus. These results demonstrated that chronic 0.05% green tea catechins administration may prevent oxidative stress related brain aging in female C57BL/6J mice.

 

 

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Author: Shigeki Yanagi and Kazuaki Matsumura and Akira Marui and Manabu Morishima and Suong-Hyu Hyon and Tadashi Ikeda and Ryuzo Sakata

Objective Ischemia–reperfusion injury is among the most serious problems in cardiac surgery. Epigallocatechin-3-gallate, a major polyphenolic component of green tea, is thought to be cardioprotective through its antioxidant activities. We investigated cardioprotective effects of oral epigallocatechin-3-gallate pretreatment against ischemia–reperfusion injury in isolated rat hearts and considered possible underlying mechanisms. Methods Rats were given epigallocatechin-3-gallate solution orally at 0.1, 1, or 10 mmol/L (n = 12 per group) for 2 weeks; controls (n = 12) received tap water alone for 2 weeks. Subsequently, Langendorff-perfused hearts were subjected to global ischemia for 30 minutes, followed by 60 minutes of reperfusion. Results Recoveries at 60 minutes after reperfusion of left ventricular developed pressure and maximum positive and minimum negative first derivatives of left ventricular pressure were significantly higher in 1-mmol/L group than in 0.1-mmol/L (P < .0001), 10-mmol/L (P < .05), and control (P < .0001) groups. Oxidative stress after reperfusion, as reflected by 8-hydroxy-2′-deoxyguanosine index, was lower in 1-mmol/L group than in control (P < .01) and 0.1-mmol/L (P < .05) groups. Western blot analysis after reperfusion showed p38 activation and active caspase-3 expression to be lower in 1-mmol/L group than in control group (P < .05). Conclusions Oral pretreatment with epigallocatechin-3-gallate preserved cardiac function after ischemia–reperfusion, an effect that may involve its antioxidative, antiapoptotic properties, although a high dose did not lead to dramatic improvement in cardiac function. Oral epigallocatechin-3-gallate pretreatment may be a novel and simple cardioprotective method for preventing perioperative cardiac dysfunction in cardiac surgery.

 

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Author: Yoon Woo Koh and Eun Chang Choi and Sung Un Kang and Hye Sook Hwang and Mi Hye Lee and JungHee Pyun and RaeHee Park and YoungDon Lee and Chul-Ho Kim

Hepatocyte growth factor (HGF) and c-Met have recently attracted a great deal of attention as prognostic indicators of patient outcome, and they are important in the control of tumor growth and invasion. Epigallocatechin-3-gallate (EGCG) has been shown to modulate multiple signal pathways in a manner that controls the unwanted proliferation and invasion of cells, thereby imparting cancer chemopreventive and therapeutic effects. In this study, we investigated the effects of EGCG in inhibiting HGF-induced tumor growth and invasion of oral cancer in vitro and in vivo. We examined the effects of EGCG on HGF-induced cell proliferation, migration, invasion, induction of apoptosis and modulation of HGF/c-Met signaling pathway in the KB oral cancer cell line. We investigated the antitumor effect and inhibition of c-Met expression by EGCG in a syngeneic mouse model (C3H/HeJ mice, SCC VII/SF cell line). HGF promoted cell proliferation, migration, invasion and induction of MMP (matrix metalloproteinase)-2 and MMP-9 in KB cells. EGCG significantly inhibited HGF-induced phosphorylation of Met and cell growth, invasion and expression of MMP-2 and MMP-9. EGCG blocked HGF-induced phosphorylation of c-Met and that of the downstream kinases AKT and ERK, and inhibition of p-AKT and p-ERK by EGCG was associated with marked increases in the phosphorylation of p38, JNK, cleaved caspase-3 and poly-ADP-ribose polymerase. In C3H/HeJ syngeneic mice, as an in vivo model, tumor growth was suppressed and apoptosis was increased by EGCG. Our results suggest that EGCG may be a potential therapeutic agent to inhibit HGF-induced tumor growth and invasion in oral cancer.

 

 

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Author: Karl J. Siebert and Atsushi A. Maekawa and P.Y. Lynn

Samples of dilute HCl intended to result in mixtures with saliva with pH levels below, near and above the level of maximum protein–polyphenol interaction were presented to panelists. Significant differences in astringency were seen, but no evidence of a decline in astringency with stronger acid. Panelists abstained from tea drinking for some time, then drank two or more cups of green tea per day for some days, and finally omitted tea drinking for a period. Salivary polyphenol levels were determined throughout the experiment. Drinking green tea resulted in a highly significant (p < 0.01) increase in salivary polyphenol levels that persisted for some days. Very dilute HCl solutions (0, 0.005, 0.006 and 0.007 N) were presented to panelists before, during and after the period of tea drinking and rated for astringency and sourness. Astringency and sourness intensity ratings increased significantly (p < 0.01) during the period of tea drinking. It appears that there is a metabolic pool of polyphenol that is influenced by dietary habits. It appears likely that the salivary polyphenol level influences perception of astringency caused by acids.

 

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Author: Dominik Kmiecik and Józef Korczak and Magdalena Rudzińska and Joanna Kobus-Cisowska and Anna Gramza-Michałowska and Marzanna Hęś

Author: Giselle Lehrke and Laura Hernaez and Sandra L. Mugliaroli and Mariana von Staszewski and Rosa J. Jagus

Acid tolerance of two strains of Listeria innocua as single strain culture and co-culture, were evaluated in liquid cheese whey after exposure to nisin, Microgard™ and green tea. Inorganic and organic acids were applied after natural antimicrobials treatments and microbial counts were made to analyze the bacterial response. The results have demonstrated that natural antimicrobials like nisin, Microgard™ and green tea, present in the liquid cheese whey, did not produce any cross-protection effects. On the contrary, in most of the cases, the antimicrobial treatment increased the susceptibility of L. innocua to acid stress, particularly in the treatment with nisin or green tea extract and organic acids. These results were corroborated by different techniques, including transmission electron microscopy.

 

 

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Author: Mark E. Stearns and Min Wang

We have examined whether epigallocatechin-3-gallate (EGCG), and extract of green tea, in combination with taxane (i.e., paclitaxel and docetaxel), exerts a synergistic activity in blocking human prostate PC-3ML tumor cell growth in vitro and in vivo. Growth assays in vitro revealed that the IC50 values were ∼30 μM, ∼3 nM, and ∼6 nM, for EGCG, paclitaxel and docetaxel, respectively. Isobolograms generated from the data clearly indicated that EGCG in combination with paclitaxel or docetaxel had an additive effect in blocking tumor cell growth. EGCG combined with taxane also had an additive effect to increase the expression of apoptotic genes, (p53, p73, p21, and caspase 3) and the percent apoptosis observed in vitro and in tumor modeling studies in severe combined immunodeficient mice. The tumor modeling studies clearly showed that EGCG plus taxane injected intraperitoneally (i.p.) induced a significant increase in apoptosis rates (TUNEL assays) and eliminated preexisting tumors generated from PC-3ML cells implanted i.p., increasing disease-free survival rates to greater than 90%. More importantly, the combination therapy (i.p. biweekly) blocked metastases after intravenous injection of PC-3ML cells through the tail vein. In mice treated with EGCG plus taxane, the disease-free survival rates increased from 0% (in untreated mice) to more than 70% to 80% in treated mice. Taken together, these data demonstrate for the first time that EGCG in combination with taxane may provide a novel therapeutic treatment of advanced prostate cancer.

 

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