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.     

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.     

从热溶性绿茶粉中提取茶多酚的试验研究

试验以热溶性茶粉为原料制备高纯度茶多酚,比较了不同浸提时间、不同乙醇浓度、不同乙醇体积的条件下,茶多酚产品的提取率;并分析了茶多酚在各个工序中的损失情况,认为乙酸乙酯萃取工序中茶多酚损失最严重;采用正交试验方法确定了茶多酚提取的最佳工艺条件为浸提时间15min、乙醇浓度65%、绿茶粉与乙醇质量体积比为1∶10。     

Physical properties and antioxidant activity of an active film from chitosan incorporated with green tea extract

An active film from chitosan incorporated with aqueous green tea extract (GTE) was developed. The effects of GTE concentrations including 2, 5, 10 and 20% (w/v) of green tea in the film-forming solution on the film properties were determined by measuring physical properties, total polyphenolic content and antioxidant activity of the active films. Fourier Transform Infrared (FTIR) spectrometry was carried out to observe the potential modifications of the chitosan films when incorporated with GTE. The results suggested that incorporation of GTE into chitosan films improved mechanical and water vapor barrier properties and enhanced polyphenolic content and antioxidant activity of the films. Changes in the FTIR spectra of the chitosan films were observed when GTE was incorporated, suggesting some interactions occurred between chitosan and the polyphenols from GTE. This study showed the benefits of incorporation of GTE into chitosan films and the potential for using the developed film as an active packaging.     

龙井绿茶茶多酚提取工艺研究

为了提高茶多酚的得率和纯度,以龙井绿茶为原料,对茶多酚进行乙醇溶液提取、超声波和微波辅助提取。醇提的最佳条件为乙醇浓度50％,浸提4次,每次45min,温度为70℃,液固比为20：1,最大浸提率为24．45％。微波辅助提取最佳条件为预浸30min,乙醇浓度40％,微波解冻档浸提4min,浸提2次,液固比为40：1,最大浸提率为24．70％。超声波辅助浸提最佳条件为乙醇浓度80％,浸提温度50℃,浸提时间25min,浸提2次,液固比为14：1,最大浸提率为24．72％。结果表明：微波与超声波提取率稍高于醇提,但三者差别不大。     

绿茶饮料中茶多酚稳定性的研究

应用分光光度法研究了绿茶饮料中茶多酚的稳定性,证明添加L-抗坏血酸1.0g/L、半胱氨酸1.0g/L、无水亚硫酸钠0.5g/L,既能在贮存过程中保持绿茶饮料特有的汤色,又能稳定其营养成分茶多酚的含量。     

茶多酚提取纯化工艺研究进展

茶多酚是一种理想的食品天然抗氧化剂,具有抗癌治病、防衰老、防辐射、消除人体自由基等多种生理功效,广泛用于食品、油脂、医药、化工等行业。近年来,对于茶多酚的提取纯化方法多见于报道,本文就国内外茶多酚提取纯化方法的研究进展情况作一综述。     

Influence of green tea polyphenols on the colloidal stability and gelation of WPC

Green tea extracts are being widely used in food products due to their health-promoting properties. Polyphenols can interact with food proteins leading to the formation of soluble or insoluble complexes; therefore they could alter functional properties of proteins. The objective of the present work was to study the colloidal stability and gelation characteristics of a whey protein concentrate (WPC) in the presence of green tea polyphenols. Mixtures of WPC35 (8 and 30% w/v) and green tea polyphenols (0.25–1% w/v) were prepared at pH 4.5 and 6.0. The size of particles formed was analyzed by light scattering, while gelation was characterized by means of dynamic rheometry and texture analysis of gels. At pH 6.0, the particles were smaller and had a higher net charge than at pH 4.5, which accounted for by a less precipitation of the system at pH 6.0. The G′ parameters of gels upon cooling at 35 °C increased with increasing polyphenols concentration at both pH values. However, the relative viscoelasticity decreased. The texture analysis indicated that the addition of polyphenols improved the firmness and adhesiveness of the gels at pH 6.0, while no significant differences were seen at pH 4.5. The results obtained in this work indicate that pH-dependent interaction between green tea polyphenols and WPC induces the formation of aggregates that modifies the viscoelastic and texture properties of the gels.     

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.     

微波辅助双水相提取绿茶中茶多酚的研究

采用微波辅助乙醇-磷酸氢二钾双水相体系提取绿茶中的茶多酚,对乙醇体积分数、磷酸氢二钾用量、提取时间、液料比和微波功率等影响因素作了详细研究与优化。实验结果表明,最佳工艺条件为:乙醇体积分数50%,磷酸氢二钾用量7.0 g,液料比50 m L·g^-1,微波功率370 W,提取时间30 s,在此条件下,茶多酚得率可达38.98%。研究结果可应用于绿茶中茶多酚的提取和绿茶品质分析。      

茶多酚对假单胞菌抑菌机理研究

以假单胞菌为研究对象,考察茶多酚的抑菌作用及其抑菌机理。首先通过平板法确定茶多酚对假单胞菌最小抑菌浓度。然后采用滤纸片法确定不同浓度的茶多酚对假单胞菌的抑菌效果。通过生化检测研究茶多酚对假单胞菌的抑菌机理。结果表明:茶多酚对假单胞菌最小抑菌浓度为0.3%;茶多酚对假单胞菌有很强的抑菌作用;当茶多酚作用于菌体细胞后,能够逐步破坏其细胞壁的完整性,使得碱性磷酸酶渗出,继而使细胞膜的通透性增加,导致金属离子、蛋白质的渗漏使细胞代谢发生紊乱,逐渐破坏细胞结构,从而起到抑菌作用。     

复合酶辅助浸提绿茶多酚工艺条件优化

采用纤维素酶+果胶酶的复合酶法在较适温度下辅助浸提绿茶多酚,以茶多酚浸提率为考察指标,通过单因素和正交实验优化了酶添加量、料液比、浸提温度和浸提时间等四个浸提条件因素,确定了最佳浸提工艺条件为:纤维素酶和果胶酶分别添加0.3%,料液比1∶40 g/m L,浸提温度50℃,浸提时间45 min;在此条件下茶多酚浸提率可达21.36%,明显高于传统水提法的茶多酚浸提率17.41%。      

茶多酚纳米脂质体对明胶膜性能的影响

以鱼皮明胶为基质,添加茶多酚纳米脂质体,制备了复合明胶膜,研究了茶多酚纳米脂质体的加入对明胶膜结构、力学性能、通透性、光吸收特性、抗氧化性能的影响。结果表明,茶多酚纳米脂质体的加入明显改变了明胶膜的结构,降低了明胶膜的拉伸强度和透湿系数,提高了断裂伸长率和透氧系数;此外,茶多酚纳米微粒的添加提高了明胶膜对鱼油的抗氧化保护效果及对DPPH自由基的清除率。      

茶叶中污染微生物分析及茶多酚抑菌性研究

对茶饮料中茶叶原料的微生物种类进行了分析、鉴定,并对茶多酚对茶叶中污染微生物的抑菌性进行了研究。结果表明,茶叶中主要污染微生物是枯草芽孢杆菌、阴沟肠杆菌和黑曲霉。当茶饮料中茶多酚含量大于0.6g/L时对枯草芽孢杆菌有很好的抑制作用,而茶多酚含量小于1.2g/L时对阴沟肠杆菌、黑曲霉无抑制作用。实验表明正常的杀菌条件可将阴沟肠杆菌和黑曲霉杀死。因此为保障产品安全,建议茶饮料的茶多酚含量大于0.6g/L。     

茶多酚测定研究进展

茶多酚是茶叶中特有的天然抗氧化物质,具有清除自由基、抗癌症突变、辅助治疗等多种功效,在食品与药品领域有着良好的应用与发展前景。不同茶叶产品中茶多酚成分组成和含量差异与其功效的发挥程度有着密不可分的关系,以茶多酚作为主要功效成分的功能性产品或药品都需要测定茶多酚含量作为其功效或疗效的依据,因此,茶多酚含量的测定十分重要。本文综述了近年来国内外茶多酚测定方法的研究进展,介绍了光谱法、色谱法、电位分析法、流动注射技术等方法在茶多酚检测中的应用现状,分析了茶多酚检测中值得关注和研究的问题,并展望了未来发展和应用的趋势。     

In vitro antioxidative and anticancer activities of tea glycoprotein in green tea

In this paper, the antioxidative and anticancer activities of tea glycoprotein (TGP) in green tea were studied. TGP was extracted from coarse old green tea and purified by Sephadex G-100 gel filtration, and its purity was determined by high performance gel permeation chromatography (HPGPC). The antioxidative activity of the TGP was evaluated by determining the change of the values of the heat-induced oxidation in a linoleic acid system with β-carotene, the decoloration of the 1,1-diphenyl-2-picrylhydrazyl (DPPH), and the superoxide generated from autoxidation of pyrogallol. The results show that the TGP possesses distinctive antioxidative activity. Furthermore, the anticancer activity of the TGP at different concentrations was evaluated by the MTT assay using two kinds of colon cancer cell lines (HCT-15, Caco-2). Dose-dependently TGP exhibited good antiproliferation activity to HCT-15, whereas exhibited very weak antiproliferation activity to Caco-2. Only at a very high concentration (409.6 μmol L⁻¹), the TGP obviously inhibited the proliferation of Caco-2. Whether there is a correlation between the antioxidative and the anticancer activity of the TGP, should be studied further.     

绿茶多酚对马铃薯淀粉壳聚糖复合膜影响研究

为开发新型抗氧化活性包装材料,以马铃薯淀粉壳聚糖复合膜为基材,研究添加绿茶多酚对复合膜抗氧化能力、物理性能和化学结构影响。结果表明:添加绿茶多酚显著（p<0.05）提高了复合膜DPPH自由基清除能力,添加2%绿茶多酚的复合膜在3 min内自由基清除率达到94.48%,绿茶多酚添加也显著（p<0.05）地增强了复合膜的阻湿性。但添加绿茶多酚增加了复合膜红色和黄色、水溶性,降低了膜的柔韧性,红外光谱显示添加绿茶多酚影响了-O-H键的弯曲和伸缩振动,干扰了复合膜体间的氢键相互作用。研究结果表明添加0.5%绿茶多酚既能提高复合膜的抗氧化能力,又可使复合膜拥有较好的柔韧性。      

茶多酚调节肠道菌群及抗肥胖作用研究进展

茶是世界上最受欢迎的饮料之一,其含有丰富的茶多酚,近来,茶多酚对肠道菌群的调节作用引起了学术界的关注。肥胖可以导致心血管疾病、糖尿病、癌症等慢性疾病,因此抗肥胖物质的研究与开发也是当下的研究热点之一,茶多酚的抗肥胖作用也是其中的重要领域。本综述总结了茶多酚、肠道菌群以及肥胖三者的作用关系,并对近5年相关的非临床以及临床研究进行了总结分析。总结发现茶多酚可以调节肠道菌群组成,而肠道菌群也可以影响茶多酚的吸收与代谢。茶多酚可以通过增加益生菌的丰度以及调节能量消耗、营养物质消化吸收、脂质分解代谢和抑制脂肪细胞合成等方式发挥抗肥胖作用。目前对于茶多酚调节肠道菌群和抗肥胖作用的研究以动物模型为主,且大多实验结果证实了茶多酚的肠道菌群调节作用及抗肥胖作用,但是作用剂量尚不明确,且茶多酚剂量毒性研究不足。另外该领域临床研究不足,需要在未来进行更大样本量和更长时间的研究,以实现茶渣等副产物的高价值利用并减少肥胖相关疾病。