Beneficial effects of tea and its polyphenols against prostate cancer

Tea, next to water, is the most widely consumed beverage in the world. Depending upon the level of fermentation, tea can be categorized into three types: green (unfermented), oolong (partially fermented), and black (highly to fully fermented). In general, green tea has been found to be superior to black and oolong tea in terms of antioxidant and health promoting benefits owing to the higher content of (-)-epigallocatechin-3-gallate. Tea polyphenols comprise about one-third of the weight of the dried leaf, and they exhibit biochemical and pharmacological activities including antioxidant activities, inhibition of cell proliferation, induction of apoptosis, cell cycle arrest and modulation of carcinogen metabolism. Several studies demonstrate that most tea polyphenols exert their effects by scavenging reactive oxygen species (ROS) since excessive production of ROS has been implicated in the development of a variety of ailments including cancer of the prostate gland (CaP). Using cell culture and animal model systems, molecular targets for these remarkable beneficial effects of green tea drinking on CaP prevention and therapy have been defined. Geographical and case-control studies are showing that green tea drinking could afford CaP chemopreventive effects in human population. In this review we attempt to summarize the experimental as well as the epidemiological basis for the possible role of tea and its polyphenols for chemoprevention and chemotherapy of CaP.     

The effect of ascorbic acid,citric acid and low pH on the extraction of green tea: How to get most out of it

Green tea seems to have a positive impact on health due to the therein-found flavanols. The amounts of these substances depend on tea preparation. In this paper, the influence of steeping time (3–7 min) and temperature (70–100 °C) on the content of the main flavanols in green tea (epicatechin EC, epicatechin gallate ECg, epigallocatechin EGC, and epigallocatechin gallate EGCg) is presented. Furthermore, additives (phosphate buffers, ascorbic acid in different amounts, and citric acid) are used to investigate the influence of pH, antioxidative, and chelating agents, simulating the addition of lemon juice or pure vitamin C.     

Effect of green tea flavonoids on Maillard browning in UHT milk

The ability of green tea flavonoids to control Maillard browning was investigated. Epicatechin (EC) and epigallocatechin gallate (EGCG) were added at levels of 0.l and 1.0 mmol/l to a glucose/glycine model system as well as into milk that was then thermally processed in a Microthermics processing system. Samples were assessed with (1) front-face fluorescence spectroscopy for Maillard browning, (2) Hunter L*, a*, and b*; and (3) sensory analysis. In the model gluocose/glycine system, EC and EGCG reduced Maillard fluorescence at the 0.1 mmol/l level, while fluorescence was negligible with added flavonoids at 1.0 mmol/l. When these flavonoids were added to milk, they reduced the production of Maillard associated fluorescence with UHT processing. EC and EGCG also reduced the ΔE (Total color difference) during thermal processing. Throughout shelf-life testing, these compounds reduced Maillard associated fluorescence in milk. Milk samples processed with these extracts were monitored by sensory analysis during extended storage. The sensory evaluation found the green tea milk samples to be of similar liking to the control milk. These flavonoids may be of use to the food industry to control Maillard browning.     

A minireview of effects of green tea on energy expenditure

In recent years, individuals have begun to tend more frequently to some natural and herbal products to be used alone or as a combination with diet and exercise for ensuring the weight loss. Green tea is the leading one of these products. In some studies, it is reported that the green tea causes an increase in thermogenesis and substrate with fat oxidation by affecting on the sympathetic nervous system. It is reported that green tea has two main components that are associated with energy expenditure. One of them is caffeine and the other is catechin content. Each of these two components has an impact on energy mechanism separately. In this minireview article, mechanisms of action and effects of caffeine and catechin, which are found in green tea composition, on energy expenditure are assessed.     

复合酶对绿茶饮料质量影响的研究

在初步确立绿茶饮料生产工艺的基础上,对几种酶进行复合后应用于绿茶饮料的最佳作用参数、作用效果及对绿茶饮料的感观、理化品质的影响进行了探讨.     

Selenium-containing green tea has higher antioxidant and prebiotic activities than regular green tea

The effects of selenium-containing green tea (SGT; 1.4 mg selenium/kg) and China green tea (CGT; 0.13 mg selenium/kg) on the in vitro growth of lactobacilli and bifidobacteria were investigated using pure and mixed cultures. SGT had significantly higher phenolic contents (TPC), higher reducing activity, higher DPPH free-radical scavenging activity, and higher ferrous-ion chelating activity (P < 0.05–0.0001) than CGT. The addition of aqueous extracts from CGT to Mann-Rogosa-Sharpe (MRS) broth at 10% and 25% (v/v) resulted in small but nonsignificant (P > 0.05) increases in the numbers of Lactobacillus rhamnosus and Bifidobacterium breve over the control incubations (without tea). Addition of 10% and 25% of SGT extract resulted in a significant increase (P < 0.05–0.0001) in the number of lactobacilli and bifidobacteria recovered from batch fermentation while CGT did not increase the number of bifidobacteria. The higher prebiotic activity of SGT over CGT may be related to the higher TPC or minerals, notably selenium or a combination of these factors. To test whether selenium itself has an effect on bacterial growth, Na-selenite and Na-selenate were added alone or in combination with CGT to the MRS broth containing pure culture of L. rhamnosus. Growth of this bacterium was enhanced relative to the control incubation of MRS only. When added in combination with CGT, Na-selenate was more effective at enhancing the growth of L. rhamnosus than Na-selenite. The prebiotic effect of SGT could be largely explained by its selenium content.     

Formation of damascenone derived from glycosidically bound precursors in green tea infusions

Damascenone is well-known for its potent flavour with an extremely low odour threshold. Several glycosidically bound precursors of damascenone have been isolated from several plants, but little is known about their occurrences in green tea infusions. In this work, three major glycosidic precursors of damascenone, 9-O-β-d-glucopyranosyl-megastigma-6,7-dien-3,5,9-triol (1a), 9-O-β-d-glucopyranosyl-3-hydroxy-7,8-didehydro-β-ionol (2a), and 3-O-β-d-glucopyranosyl-3-hydroxy-7,8-didehydro-β-ionol (2b) were isolated and identified in green tea infusions, and the stereochemistries at C-3 and C-9 positions of aglycone parts of the three glycosidic precursors were determined as (3S, 9R)-1a, (3R, 9R)-2a, and (3R, 9R)-2b, respectively. Compounds 1a, 2a, and 2b as well as 3-O-β-d-glucopyranosyl-megastigma-6,7-dien-3,5,9-triol (1b) were hydrolysed to form damascenone in a model system with strong acidic conditions (pH 2.0) and at high temperature (90 °C). In contrast to hydrolysis of 2a and 2b, more damascenone was transformed from 1a and 1b. Furthermore, the β-d-glucosyl moiety at the C-3 position gave a higher dehydration rate from megastigma-6,7-dien-3,5,9-triol to 3-hydroxy-7,8-didehydro-β-ionol than compound 1a carrying the sugar residue at C-9 position. Interestingly, the four glycosidic precursors of damascenone were not hydrolysed to give damascenone under slightly acidic conditions (pH 5.4 and 120 °C for 10 min), but they could be transformed to damascenone in the presence of green tea infusions even under the equal conditions.     

Characterisation of polysaccharides from green tea of Huangshan Maofeng with antioxidant and hepatoprotective effects

This study was to examine the hepatoprotective effects of polysaccharides from green tea of Huangshan Maofeng (HMTP) against CCl₄-induced oxidative damage in mice. HMTP is an acidic heteropolysaccharide with galactose (35.0%, mol.%), arabinose (28.9%) and galacturonic acid (11.3%) being the main monosaccharide components. HMTP (400 and 800 mg/kg·bw) administered orally daily for 14 days before CCl₄ administration significantly reduced the impact of CCl₄ toxicity on the serum markers of liver damage, alanine aminotransferase, aspartate aminotransferase, total-cholesterol and triglycerides. This method of HMTP administration also markedly restrained hepatic lipid peroxidation formation of malondialdehyde and 15-F_2t isoprostanes, and elevated the antioxidant levels of hepatic glutathione and superoxide dismutase. These results together with liver histopathology indicated that HMTP exhibited hepatoprotection against CCl₄-induced injury, which was found to be comparable to that of biphenyldicarboxylate. The hepatoprotective effects of HMTP may be due to both the inhibition of lipid peroxidation and the increase of antioxidant activity.     

发酵型绿茶黄瓜酸乳的研制

以绿茶、黄瓜、全脂奶粉、蔗糖为主要原料,通过保加利亚乳酸杆菌和嗜热链球菌发酵,研制出一种新型的绿茶黄瓜酸乳。确定了黄瓜护色的最佳条件为Zn(COOH)2浓度0.2g/L,护色温度90℃,时间2min。采用正交实验法筛选出最佳工艺条件黄瓜汁10%、蔗糖量6%、茶叶量0.3%、接种量2.5%,发酵时间5h,发酵温度43℃。实验结果表明产品各项理化指标都符合国家卫生标准。     

Molecular mechanisms of green tea polyphenols with protective effects against skin photoaging

Whereas green tea has historically been consumed in high quantities in Northeast Asia, its popularity is also increasing in many Western countries. Green tea is an abundant source of plant polyphenols exhibiting numerous effects that are potentially beneficial for human health. Accumulating evidence suggests that green tea polyphenols confer protective effects on the skin against ultraviolet (UV) irradiation-induced acceleration of skin aging, involving antimelanogenic, antiwrinkle, antioxidant, and anti-inflammatory effects as well as prevention of immunosuppression. Melanin pigmentation in the skin is a major defense mechanism against UV irradiation, but pigmentation abnormalities such as melasma, freckles, senile lentigines, and other forms of melanin hyperpigmentation can also cause serious health and aesthetic issues. Furthermore, UV irradiation initiates the degradation of fibrillar collagen and elastic fibers, promoting the process of skin aging through deep wrinkle formation and loss of tissue elasticity. UV irradiation-induced formation of free radicals also contributes to accelerated photoaging. Additionally, immunosuppression caused by UV irradiation plays an important role in photoaging and skin carcinogenesis. In this review, we summarize the current literature regarding the antimelanogenic, antiwrinkle, antioxidant, and immunosuppression preventive mechanisms of green tea polyphenols that have been demonstrated to protect against UV irradiation-stimulated skin photoaging, and gauge the quality of evidence supporting the need for clinical studies using green tea polyphenols as anti-photoaging agents in novel cosmeceuticals.     

绿茶饮料的制备及品质控制

研究了影响绿茶色香味因素，探讨了绿茶饮料沉淀形成了变色的机理，得出茶水比1：100，浸提温度85℃，浸提时间10in为最佳萃取工艺条件，同时采用茶汁pH值为5．5，木瓜蛋白酶添加量为0.05g/100ml茶汁，β－CD添加量1.0g/500ml,Vc0.1g/500ml,D-葡萄糖酸－δ－内脂0.1g/500ml，可有效防止沉淀的产生和色泽的变化，得到满意的产品质量。     

Comparison of bioactive components in GABA tea and green tea produced in Taiwan

The aim of this study is to investigate the bioactive components of GABA (γ-aminobutyric acid) tea as compared with green tea produced in Taiwan. Using in total 56 tea samples (28 green tea and 28 GABA tea), moisture content, Hunter L, a and b values, phenolic compounds, amino acids including GABA, fatty acids and ascorbic acid were determined. The results showed that moisture, total free amino acids, crude fat, Hunter L value, total nitrogen, free fatty acids and reducing sugar did not differ significantly between GABA tea and green tea. However, GABA tea had higher Hunter a and b values, while green tea had higher total catechin and ascorbic acid contents (p < 0.05). Of major catechins, epicatechin and epigallocatechin gallate were found to be lower in GABA tea than in green tea. For free amino acids, GABA, alanine, ammonia, lysine, leucine and isoleucine were found to be significantly higher in GABA tea, while the glutamic acid, aspartic acid, and phenylalanine were higher in green tea (p < 0.05). Theanine, tryptophan, valine, threonine and methionine were not found to be different between the two kinds of tea.     

不同温湿度与包装条件对茶叶干品贮藏的影响

通过短时间的模拟实验，研究了不同温度、湿度条件及包装材料对茶叶贮藏的影响。茶叶的考察指标为维生素C、茶多酚及色差和主要感官变化。结果表明，茶叶在环境湿度下冷藏就可以达到较高的贮藏要求，包装材料以玻璃瓶为宜。     

Hydrolysis of epigallocatechin gallate using a tannase from Paecilomyces variotii

Epigallocatechin (EGC) and gallic acid (GA) were prepared by the degalloylation of an epigallocatechin gallate (EGCG) extract from green tea. EGCG was entirely hydrolyzed using a tannase (from Paecilomyces variotii) at pH 6.0, incubating at 40 °C for 30 min. The antiradical properties and the reducing power of these samples were assessed using the DPPH and FRAP assays, respectively. This work established a relationship between the antioxidant effects of epigallocatechin gallate and the enzymatic reaction products (epigalocatechin and gallic acid). The enzymatic reaction products showed higher scavenging activity and antioxidant capacity when compared to epigallocatechin gallate.     

胡萝卜绿茶酸乳工艺研究

以胡萝卜、绿茶、牛乳、蔗糖为主要原料，进行发酵工艺实验，通过正交实验确定了酸乳原料的最佳配方：茶叶0．5％、胡萝卜汁15％、蔗糖7％，菌种选用保加利亚乳杆菌和嗜热链球菌（1：1），接种量3％。     

绿茶中表没食子儿茶素没食子酸酯生物活性研究进展

表没食子儿茶素没食子酸酯（EGCG）是从绿茶中提取的多酚物质含量最高的一种水溶性活性成分,在茶叶中约占到茶叶毛质量的7%～13%,也是茶多酚类物质中最具生理活性的物质。在现阶段植物和植物衍生物因其具有低副作用和在自然界中具有高可用性,作为发现和开发新抗菌和抗病毒药物的天然来源而备受关注。该综述总结了近几年绿茶中EGCG在抗病毒、抗菌、抗肿瘤、抗炎等方面的研究进展,为我国茶叶在健康产业中的应用提供理论支撑。     

Epimerisation of tea polyphenols in tea drinks

The present study was carried out to quantify green tea epicatechin (GTE) derivatives and to investigate the origin of epicatechin epimers present in 18 selected canned or bottled tea drinks. The major GTEs present in tea are (?)‐epigallocatechin gallate (EGCG), (?)‐epigallocatechin (EGC), (?)‐epicatechin gallate (ECG) and (?)‐epicatechin (EC). HPLC analysis showed that the content of total GTEs was lower (16.4–268.3 mg l^?1) in the canned and bottled tea drinks than in tea traditionally prepared as a beverage in a cup or teapot (3–5 g l^?1). The major finding was that they contained higher levels of epicatechin epimers, namely (?)‐gallocatechin gallate (GCG), (?)‐gallocatechin (GC), catechin gallate (CG) and (?)‐catechin (C), than of GTEs, ranging from 7.6 to 331.8 mg l^?1. To investigate the origin of these epimers, GTEs were extracted from longjing green tea and autoclaved at various temperatures for 10–60 min. It was found that at least 50% of GTEs were epimerised to their corresponding epimers when autoclaved at 120 °C for 20 min. It is concluded that epicatechin epimers in tea drinks are not originally present in green tea leaf but are instead derived from thermal conversion of GTEs. Copyright © 2003 Society of Chemical Industry