Research Database

Author: Wenping Tang and Shiming Li and Yue Liu and Mou-Tuan Huang and Chi-Tang Ho

Tea is one of the most popular beverages worldwide. The variety of tea and tea extracts in the market has different polyphenol profiles, which are the bioactive chemical entities. In searching for efficacious molecules from tea against hyperglycaemia, we performed a direct comparison between green tea extracts (GTE) and black tea extracts (BTE), which have been chemically well-characterized by HPLC, in a type 2 diabetic mouse model combining low dose streptozotocin (STZ) with high fat (HF) diet. The results revealed that both GTE and BTE in drinking water substantially lowered blood glucose levels and ameliorated glucose intolerance, but GTE was more effective in anti-hyperglycaemic activity and in lowering body weight gain. GTE was also more effective than BTE in reversing histological deterioration of liver in the diabetic mice. Serum insulin levels significantly increased in BTE group but not in GTE group, suggesting that they might exert their hypoglycaemic effects through different pathways. We explored the possible mechanisms by homeostatic model assessment (HOMA), and results showed that the predominant mechanism for the anti-diabetic effect of GTE was through insulin resistance, while for BTE it was through insulin secretion.

 

 

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Author: Chia-Fang Tsai and Yu-Wen Hsu and Hung-Chih Ting and Chun-Fa Huang and Cheng-Chieh Yen

 

The in vivo antioxidant and antifibrotic properties of green tea (Camellia sinensis, Theaceae) were investigated with a study of carbon tetrachloride (CCl4)-induced oxidative stress and hepatic fibrosis in male ICR mice. Oral administration of green tea extract at doses of 125, 625 and 1250 mg/kg for 8 weeks significantly reduced (p < 0.05) the levels of thiobarbituric acid-reactive substances (TBARS) and protein carbonyls in the liver by at least 28% compared with that was induced by CCl4 (1 mL/kg) in mice. Moreover, green tea extract administration significantly increased (p < 0.05) the activities of catalase, glutathione peroxidase (GSH-Px) and glutathione reductase (GSH-Rd) in the liver. Our study found that oral administration of green tea extract prevented CCl4-induced hepatic fibrosis, as evidenced by a decreased hydroxyproline level in the liver and a reduced incidence of hepatic fibrosis by histological observations. These results indicate that green tea exhibits potent protective effects against CCl4-induced oxidative stress and hepatic fibrosis in mice by inhibiting oxidative damage and increasing antioxidant enzyme activities.

 

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Author: Lucie Trnková and Daniela Ricci and Caterina Grillo and Gianni Colotti and Fabio Altieri

Background Green tea is a rich source of polyphenols, mainly catechins (flavanols), which significantly contribute to the beneficial health effects of green tea in the prevention and treatment of various diseases. In this study the effects of four green tea catechins on protein ERp57, also known as protein disulfide isomerase isoform A3 (PDIA3), have been investigated in an in vitro model. Methods The interaction of catechins with ERp57 was explored by fluorescence quenching and surface plasmon resonance techniques and their effect on ERp57 activities was investigated. Results A higher affinity was observed for galloylated cathechins, which bind close to the thioredoxin-like redox-sensitive active sites of the protein, with a preference for the oxidized form. The effects of these catechins on ERp57 properties were also investigated and a moderate inhibition of the reductase activity of ERp57 was observed as well as a strong inhibition of ERp57 DNA binding activity. Conclusions Considering the high affinity of galloylated catechins for ERp57 and their capability to inhibit ERp57 binding to other macromolecular ligands, some effects of catechins interaction with this protein on eukaryotic cells may be expected. General significance This study provides information to better understand the molecular mechanisms underlying the biological activities of catechins and to design new polyphenol-based ERp57-specific inhibitors.

 

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Author: S.P.J. Namal Senanayake

Green tea is one of the most popular and extensively used dietary supplement in the United States. Diverse health claims have made for green tea as a trendy ingredient in the growing market for nutraceuticals and functional foods. Green tea extract contains several polyphenolic components with antioxidant properties, but the predominant active components are the flavanol monomers known as catechins, where epigallocatechin-3-gallate and epicatechin-3-gallate are the most effective antioxidant compounds. Additional active components of green tea extract include the other catechins such as epicatechin and epigallocatechin. Among these, epigallocatechin-3-gallate is the most bioactive and the most scrutinized one. Green tea polyphenols are also responsible for distinctive aroma, color and taste. Green tea extract can also be used in lipid-bearing foods to delay lipid oxidation and to enhance the shelf-life of various food products. This review outlines the chemistry, flavour components, antioxidant mechanism, regulatory status, food applications, and stability of green tea extract in food.

 

 

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Author: Arpita Basu and Nancy M. Betts and Afework Mulugeta and Capella Tong and Emily Newman and Timothy J. Lyons

Green tea, a popular polyphenol-containing beverage, has been shown to alleviate clinical features of the metabolic syndrome. However, its effects in endogenous antioxidant biomarkers are not clearly understood. Thus, we tested the hypothesis that green tea supplementation will upregulate antioxidant parameters (enzymatic and nonenzymatic) in adults with the metabolic syndrome. Thirty-five obese participants with the metabolic syndrome were randomly assigned to receive one of the following for 8 weeks: green tea (4 cups per day), control (4 cups water per day), or green tea extract (2 capsules and 4 cups water per day). Blood samples and dietary information were collected at baseline (0 week) and 8 weeks of the study. Circulating carotenoids (α-carotene, β-carotene, lycopene) and tocopherols (α-tocopherol, γ-tocopherol) and trace elements were measured using high-performance liquid chromatography and inductively coupled plasma mass spectroscopy, respectively. Serum antioxidant enzymes (glutathione peroxidase, glutathione, catalase) and plasma antioxidant capacity were measured spectrophotometrically. Green tea beverage and green tea extract significantly increased plasma antioxidant capacity (1.5 to 2.3 μmol/L and 1.2 to 2.5 μmol/L, respectively; P < .05) and whole blood glutathione (1783 to 2395 μg/g hemoglobin and 1905 to 2751 μg/g hemoglobin, respectively; P < .05) vs controls at 8 weeks. No effects were noted in serum levels of carotenoids and tocopherols and glutathione peroxidase and catalase activities. Green tea extract significantly reduced plasma iron vs baseline (128 to 92μg/dL, P < .02), whereas copper, zinc, and selenium were not affected. These results support the hypothesis that green tea may provide antioxidant protection in the metabolic syndrome.

 

 

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Author: Marcia da Silva Pinto

Although among the five main types of teas (white, green, oolong, black and pu-erh), black tea is the most consumed worldwide, an impressive number of scientific publications have been focused on green tea and its major compounds, flavan-3-ols (“catechins”). However, besides flavan-3-ols, there are other compounds present in tea that could be accounted as potential bioactive compounds. Therefore, the objective of the present review is to provide a new perspective on the health benefits associated with tea consumption by critically analyzing the available literature on the potential tea bioactive compounds and the current level of scientific evidence for these health benefits. Until now the exact mechanisms of action or compounds responsible for the health benefits associated with tea consumption have only been poorly investigated. It is important to consider that tea compounds will be extensively metabolized to different metabolites that will, most likely, be the compounds circulating in blood and potentially reaching the different sites of action.

 

 

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Author: Pooja Bhardwaj and Deepa Khanna

Green tea, Camellia sinensis (Theaceae), a major source of flavonoids such as catechins, has recently shown multiple cardiovascular health benefits through various experimental and clinical studies. These studies suggest that green tea catechins prevent the incidence of detrimental cardiovascular events, and also lower the cardiovascular mortality rate. Catechins present in green tea have the ability to prevent atherosclerosis, hypertension, endothelial dysfunction, ischemic heart diseases, cardiomyopathy, cardiac hypertrophy and congestive heart failure by decreasing oxidative stress, preventing inflammatory events, reducing platelet aggregation and halting the proliferation of vascular smooth muscle cells. Catechins afford an anti-oxidant effect by inducing anti-oxidant enzymes, inhibiting pro-oxidant enzymes and scavenging free radicals. Catechins present anti-inflammatory activity through the inhibition of transcriptional factor NF-κB-mediated production of cytokines and adhesion molecules. Green tea catechins interfere with vascular growth factors and thus inhibit vascular smooth muscle cell proliferation, and also inhibit thrombogenesis by suppressing platelet adhesion. Additionally, catechins could protect vascular endothelial cells and enhance vascular integrity and regulate blood pressure. In this review various experimental and clinical studies suggesting the role of green tea catechins against the markers of cardiovascular disorders and the underlying mechanisms for these actions are discussed.

 

 

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Author: K. Ide and N. Wakamiya and M. Park and N. Takuma and S. Fujii and A. Nakahara and T. Suzuki and J. Nakase and Y. Ukawa and Y.M. Sagesaka and H. Yamada

Background: In rapidly aging societies worldwide, the number of patients with disorders marked by cognitive dysfunction, such as Alzheimer's disease, is gradually increasing; however, thus far, no fundamental curative therapy has been established. Green tea, whose major constituents are catechins and theanine, is known to have various health benefits for humans. However, the effects of green tea consumption on cognitive dysfunction remain to be clinically verified. Objective: To conduct a clinical study to investigate the effects of green tea consumption on cognitive dysfunction. Patients and methods: Twelve elderly nursing home residents (2 men, 10 women; mean age, 88 years) with cognitive dysfunction (Mini Mental State Examination [MMSE] score: <28) were recruited. Written informed consent was obtained from the patients and caregivers. The patients were asked to consume green tea powder (2 g/day [containing 227 mg of catechins and 37 g of theanine]; manufactured by ITO EN Ltd., Tokyo) for 3 months. Cognitive function was assessed by performing MMSE, and serum lipid levels were measured. Results: The MMSE scores (mean ± S.D.) significantly improved after the intervention (before intervention, 15.3 ± 7.7; after intervention, 17.0 ± 8.2; p = 0.025), especially for the category recent memory. Regarding serum lipid levels, low-density lipoprotein (LDL)-cholesterol levels remained unaltered, but triglyceride levels decreased significantly (before intervention, 124 ± 80 mg/dL; after intervention, 103 ± 57 mg/ dL; p = 0.041). Conclusion: These results suggest that green tea consumption may be effective in improving cognitive function, and additional confirmatory long-term controlled studies are needed. 

 

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Author: Abdul-Lateef Molan

 

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Author: Sha-Sha BAI and Zhi LI and Xiao-Huan ZANG and Chun WANG and Zhi WANG

A novel analytical method was developed for the extraction and determination of five chloroacetanilide herbicides (alachlor, acetochlor, metolachlor, butachlor and pretilachlor) in water and green tea samples by graphene-based magnetic solid phase extraction and dispersive liquid-liquid microextraction followed by gas chromatography-flame ionization detection (GC-FID). Some important experimental parameters that could influence the extraction efficiency were investigated. Under the optimum conditions, as high as 3399 to 4002 fold enrichment factors for the herbicides were achieved. A good linearity was obtained in the range of 0.1–50.0 μg L−1 for all the five herbicides with the correlation coefficients (r) varying from 0.9973 to 0.9993. The limits of detection ranged from 0.01 to 0.03μg L−1. The method was applied to the analysis of the chloroacetanilide herbicides in environmental water and green tea samples with a satisfactory result. The recoveries of the method for the analytes were in the range from 80.2% to 105.3%, and the relative standard deviations were between 3.8% and 5.8%.

 

 

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