茶多酚和TBHQ对花生油、花生大豆调和油抗氧化作用的对比研究

利用对比试验和强制氧化方法研究了茶多酚和特丁基对苯二酚(TBHQ)等抗氧化剂对压榨一级花生油、花生大豆调和油的抗氧化作用。     

茶树花多酚提取工艺的研究

用常规水浴浸提法和超声波辅助浸提法来提取茶树花中的多酚，研究了浸提温度、时间、料液比等因素对多酚得率的影响，比较得出超声波辅助浸提用时短，温度低的优点；通过正交试验设计，研究了各因素对多酚浸提影响的主次顺序，确定了最佳提取参数。实验结果采用统计软件（SPSS）进行分析，影响超声波辅助浸提各因素的主次顺序为料液比、温度、浸提时间,超声波辅助浸提最佳工艺为：温度50℃、提取时间10min、料液比1：30，在此工艺条件下多酚浸提得率75．13ms／g干花。为茶树花资源深度研究开发提供依据。     

Changes in content of organic acids and tea polyphenols during kombucha tea fermentation

Kombucha tea is a fermented tea beverage produced by fermenting sugared black tea with tea fungus (kombucha). Tea polyphenols which includes (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG) and theaflavin (TF) have been reported to possess various biological activities. The present study focused on changes in content of organic acid and tea polyphenols in kombucha tea prepared from green tea (GTK), black tea (BTK) and tea manufacture waste (TWK) during fermentation. Concentration of acetic acid has reached maximum up to 9.5 g/l in GTK on 15th day and glucuronic acid concentration was reached maximum upto 2.3 g/l in BTK on 12th day of fermentation. Very less concentration of lactic acid was observed during the fermentation period and citric acid was detected only on 3rd day of fermentation in GTK and BTK but not in TWK. When compared to BTK and TWK very less degradation of EGCG (18%) and ECG (23%) was observed in GTK. TF and thearubigen (TR) were relatively stable when compared to epicatechin isomers. The biodegradation of tea catechins, TF and TR during kombucha fermentation might be due to some unknown enzymes excreted by yeasts and bacteria in kombucha culture.     

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.     

Mechanisms of hypolipidemic and anti-obesity effects of tea and tea polyphenols

Among the health-promoting effects of tea and tea polyphenols, the cancer-chemopreventive effects in various animal model systems have been intensively investigated; meanwhile, the hypolipidemic and antiobesity effects in animals and humans have also become a hot issue for molecular nutrition and food research. It has been demonstrated that the body weights of rats and their plasma triglyceride, cholesterol, and LDL-cholesterol have been significantly reduced by feedings of oolong, black, pu-erh, and green tea leaves to the animals. It has been suggested that the inhibition of growth and suppression of lipogenesis in MCF-7 breast cancer cells may be through down-regulation of fatty acid synthase gene expression in the nucleus and stimulation of cell energy expenditure in the mitochondria. The experimental data indicated that the molecular mechanisms of fatty acid synthase gene suppression by tea polyphenols (EGCG, theaflavins) may invite down-regulation of EGFR/PI3K/Akt/Sp-1 signal transduction pathways.     

Antioxidant activities of crude tea polyphenols, polysaccharides and proteins of selenium-enriched tea and regular green tea

The crude tea polyphenols, polysaccharides and proteins of regular green tea and Se-enriched green tea were investigated in vitro for antioxidant activities by auto-oxidation test (AAPH) and α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging method. Results showed that crude tea polyphenols of Se-enriched green tea provided the highest antioxidant activity by DPPH assay and the antioxidant activity was decreased in the order: crude tea polyphenols > crude tea proteins > tea polysaccharides. The crude protein of Se-enriched green tea was found to exhibit the highest antioxidant activity by AAPH method and the antioxidant activity was decreased in the order: crude tea proteins > tea polyphenols > tea polysaccharides. Tea polyphenols and tea polysaccharides of Se-enriched green tea presented significantly higher antioxidant activities than that of regular green tea. No significant difference of antioxidant activities was found between crude tea proteins of Se-enriched green tea and regular green tea. The combinations of Se with tea polyphenols and tea polysaccharides were responsible for the higher antioxidant activities of Se-enriched green tea than regular green tea.     

茶多酚中微量铝的测定

采用改进的铬天青S分光光度法测定了茶多酚中的微量铝。铝标准溶液浓度在1．0-11．0μg／mL之间线性关系，回归方程Y=0．10267＋0．0225X，相关系数r=0．9997，RSD=0．2％，加标回收率在95．15％-106．12％之间。本法用于茶多酚中微量铝的测定简便、快速，结果准确，令人满意。     

茶多酚分离制备的新工艺

茶叶用８０％乙醇水溶液在５０℃恒温浸提两次，每次３０ｍｉｎ，浓缩浸提液，经Ｔ３５２复合物溶液进行脱色、乙酸乙酯提纯、柠檬酸水溶液洗涤后，减压浓缩回收乙酸乙酯，茶多酚得率为１３．００％，茶多酚的纯度及咖啡因含量分别为９６．４２％、３．６６％。     

Isolation and characterization of melanic pigments derived from tea and tea polyphenols

The dark brown pigments derived from tea and tea polyphenols were studied. Physical and chemical properties revealed that pigments directly extracted from tea leaves and derived from tea polyphenols were similar to typical melanins. Further investigation showed that both melanic pigments possessed similar antioxidant capability, due to their chelating and scavenging properties. The inhibitory effect of melanic pigments, either from tea or tea polyphenols, was significantly stronger than that of non-treated tea polyphenols. According to these properties, we have extracted melanin from tea. In addition, oxidation of tea polyphenols also provided an alternative method to maximize the yields. The extracted melanin is an antioxidant, which interrupted free radical reactions at a step in the development chain by its scavenging properties and, at the step of initiation, by its ability to chelate metals.     

脂溶性茶多酚抗氧化性能的研究及应用

利用溶剂法、乳化法和分子修饰法等技术对茶多酚进行改性,以制备具有较好脂溶性的改性茶多酚一直是国内外研究的热点之一。本文就目前用于茶多酚改性的三种方法及其优缺点,以及改性后的脂溶性茶多酚的抗氧化性能与机理进行综述和总结,并例举普丽美地生物科技(杭州)有限公司生产的脂溶性茶多酚在油脂、烘培食品、肉制品、调味品、宠物食品等领域的应用。     

Stability of tea polyphenols solution with different pH at different temperatures

Although tea polyphenols possess a variety of biological activities, the oxidative stability of tea polyphenols limits its application in the diet as preventive medicine. To enlarge biological activity of tea polyphenols, we investigated changes of tea polyphenols with different pH (3, 4, 5, 6, and 7) at different temperatures (4, 25, and 100°C). Changes in transmittance, deterioration, color values, and contents of catechins were evaluated. The results showed that tea polyphenols with a pH of 3–6 remained stable at 4 and 25°C. With increase of temperature, the tea polyphenol solutions became darker and less green, but deeper yellow in color. When the heating temperature was 100°C, a significant reduction in both total catechins and transmittance was observed. Individual catechins undergo epimerization in this process. Not only temperature and pH, but also heating time influenced the epimerization. Total contents of catechins incubated in pH 3, 4, 5, 6, and 7 citrate buffer solutions for 24 h declined by 15, 24, 41, 57, and 96% at 100°C, respectively. Therefore, tea polyphenols were pH-sensitive: the lower the pH, the more stable the tea polyphenols during storage. Storing at low temperature and acidic pH conditions did not significantly affect the characteristics of tea polyphenols.