红茶、绿茶、乌龙茶活性成分抗氧化性研究

目的与方法：通过醇提得到各种茶多酚提取液,酒石酸亚铁法测定了多酚的含量;水提得到各种茶多糖提取液,用硫酸- 苯酚法测定其中多糖的含量。通过DPPH·法、水杨酸法及邻苯三酚法测定不同茶叶中多酚、多糖含量对自由基的清除作用的影响,对比研究八种茶叶的抗氧化能力。结果：不同茶叶中多糖的含量从2.19%增大到2.89% (半发酵乌龙茶＞红茶＞绿茶),抗氧化能力：红茶＞绿茶＞乌龙茶(DPPH·法);红茶＞绿茶＞乌龙茶(水杨酸法);红茶＞乌龙茶＞绿茶(邻苯三酚法);不同茶叶中多酚的含量从1.71% 增大到9.75% (绿茶＞半发酵乌龙茶＞红茶);结论：茶多糖和多酚是茶叶的主要抗氧化成分。绿茶的抗氧化作用主要来自茶多酚,红茶的抗氧化作用主要来自茶多糖。除乌龙茶多糖提取液外,两种抗氧化成分的抗氧化能力与其含量成量效关系。     

凤凰单枞乌龙茶抗氧化特性研究

本文研究了凤凰单枞乌龙茶、绿茶(龙井和碧螺春)以及红茶(滇红和英德红茶)水浸出物的抗氧化特性。结果表明凤凰单枞乌龙茶具有较多的水浸出物,并富含茶多酚、氨基酸、可溶性糖;同时表现出较高的DPPH、超氧阴离子和羟自由基清除能力和抑制油脂过氧化特性,与绿茶水浸出物的抗氧化能力相似,显著高于红茶。这与凤凰单枞乌龙茶的水浸出物中存在较高含量的茶多酚、茶黄素和茶红素,特别是与其中的儿茶素类密切相关。     

Effect of consecutive steeping on antioxidant potential of green,oolong and black tea

After water, tea is considered to be one of the most consumed drinks worldwide. To get the maximum benefit from the whole‐leaf teas, the manufacturers provide instruction that these teas can be steeped 2–3 times over 6–8 h. In this study, the effect of consecutive steeping on radical‐scavenging ability of whole leaf green tea (unfermented), oolong tea (partially fermented) and black tea (fully fermented) was determined. Green tea showed the highest level of antioxidant activity, total phenolic and flavonoid content followed by oolong tea and black tea irrespective of the number of steeping done. The result also demonstrated that re‐steeping reduced the antioxidant potential of teas. Moreover, it was revealed that green tea is the best candidate for re‐steeping followed by oolong and then black tea.     

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.     

Analysis of metabolic markers of tea origin by UHPLC and high resolution mass spectrometry

Tea is an infusion made from the dried leaves of Camellia sinensis L. and is the second most consumed beverage in the world. It has been shown that factors such as fermentation methods, cultivar, geographical origin and season can affect the biochemical composition of tea. In this study, the biochemical composition of green, oolong and black commercial tea samples from around the world was studied using a non-targeted method utilising reversed phase ultra high pressure liquid chromatography (UHPLC) and high resolution mass spectrometry. Principal component analysis of green, oolong and black tea extracts clearly showed that fermented tea can be resolved from non-fermented tea. When the non-targeted data were combined with the supervised multivariate technique, partial least squares discriminant analysis, the method was able to clearly distinguish ‘country of origin’ within green tea and to a lesser extent within a black tea sample set, plus provide indicative marker ions for the country of origin. Many of the significant components detected in this study are unknowns, emphasising the importance of un-biased non-targeted analytical techniques. This study highlights the potential efficacy of non-targeted UHPLC–mass spectrometry when combined with multivariate statistics to differentiate fermented from non-fermented tea and provide potential indicators of provenance of tea samples for further examination.     

Tea and Its Consumption: Benefits and Risks

The recent convention of introducing phytochemicals to support the immune system or combat diseases is a centuries’ old tradition. Nutritional support is an emerging advancement in the domain of diet-based therapies; tea and its constituents are one of the significant components of these strategies to maintain the health and reduce the risk of various malignancies. Tea is the most frequently consumed beverage worldwide, besides water. All the three most popular types of tea, green (unfermented), black (fully fermented), and oolong (semifermented), are manufactured from the leaves of the plant Camellia sinensis. Tea possesses significant antioxidative, anti-inflammatory, antimicrobial, anticarcinogenic, antihypertensive, neuroprotective, cholesterol-lowering, and thermogenic properties. Several research investigations, epidemiological studies, and meta-analyses suggest that tea and its bioactive polyphenolic constituents have numerous beneficial effects on health, including the prevention of many diseases, such as cancer, diabetes, arthritis, cardiovascular disease (CVD), stroke, genital warts, and obesity. Controversies regarding beneficialts and risks of tea consumption still exist but the limitless health-promoting benefits of tea outclass its few reported toxic effects. However, with significant rise in the scientific investigation of role of tea in human life, this review is intended to highlight the beneficial effects and risks associated with tea consumption.     

Determination of catechins and flavonol glycosides in Chinese tea varieties

A standardised profiling method based on high performance liquid chromatography combined with ultraviolet (UV) and mass spectrometric detection (MS) was established to analyse the phenolic compounds of selected tea varieties used for manufacturing of green, black and oolong teas. The composition and content of 24 tea constituents were analysed, including catechins, flavonol and flavones glycosides, phenolic acids and purine alkaloids. Each tea variety had a unique chemical profile. The compositions of catechins were lower in the tea varieties for green tea manufacturing, while the content of myricetin glycosides was the lowest in the tea variety for oolong tea manufacturing. The content of individual phenolic compounds in the selected tea varieties is highly variable. However, the content of total catechins is proposed to be helpful to classify tea according to the future application as non fermented green and fermented oolong or black tea.     

Retardation of lipid oxidation in blue sprat by hot water tea extracts

The blue sprat is a small fish belonging to the family Clupeidae. Deterioration of its freshness after catching is so rapid that the fish is cooked in simple ways and consumed locally. The prooxidant activity of the skin, dark meat and ordinary meat was much higher than that of other fishes such jack mackerel. Suppression of lipid peroxidation in blue sprat was attempted using hot‐water extracts of five types of Taiwanese tea with different degrees of fermentation, ie Longjing‐type green tea, Shy Jih Chuen oolong tea, Tungting oolong tea, Pouchong tea and black tea. All the tea extracts showed antioxidant activity on oxidation of linoleic acid induced by the extracts of blue sprat's tissues. The antioxidant activity of each tea extract showed a positive correlation with the contents of total catechins, especially with that of epigallocatechin gallate, but a poor correlation with the contents of total polyphenols. The Tungting oolong tea together with Chinese green tea effectively suppressed the prooxidant activities of the dark meat and skin of blue sprat. Impregnation of blue sprat in the extract of the Tungting oolong tea retarded the lipid oxidation in fish meat assessed by peroxide value and carbonyl value during refrigeration. Copyright © 2005 Society of Chemical Industry     

饮茶和食管癌关系的研究进展

茶是除水以外消耗最多的一种饮料,在日常生活中随处可见。茶多酚是茶叶中主要的活性成分之一,研究表明,茶多酚具有抗氧化、抗肿瘤等作用,可作为癌症的保护因素。而喜食烫食可能会损伤食管黏膜,使食道上皮细胞脱落、更新加快,从而增加食管癌的发病风险。关于饮茶与食管癌关系的研究至今还没有得到一致的结论。本文主要从茶的消耗量、茶的种类、饮茶温度3 方面对近年来茶和食管癌关系的研究进行综述,并对未来的研究重点进行展望。     

高效液相色谱法分析武夷岩茶中的生物碱含量

选取10种典型武夷岩茶(5种肉桂和5种水仙)作为研究对象,以绿茶、铁观音和红茶为对照,通过高效液相色谱法检测样品叶片及冲泡茶汤中的可可碱、茶碱和咖啡碱含量,并依据各样品的生物碱含量进行主成分分析。试验结果发现,武夷岩茶叶片中的咖啡碱、可可碱和茶碱含量分别约占茶叶干重的2.341%,0.065%,0.011%,低于绿茶、铁观音和红茶;茶叶经过60s沸水冲泡后,约46.56%,46.36%,50.15%的咖啡碱、可可碱和茶碱溶于茶汤中。此外,通过主成分分析发现,武夷岩茶的3种生物碱含量与绿茶、铁观音和红茶的生物碱含量有显著差异。     

六大茶类对部分肠道致病菌抑菌效果的研究

对比分析六大茶类的抑菌效果,探讨饮茶预防肠道病的可能性。采用倍比稀释法和牛津杯法,对绿茶、红茶、乌龙茶、黄茶、白茶和黑茶六大茶类抑制肠道致病菌大肠埃希氏菌和金黄色葡萄球菌的作用进行测定。结果显示,6种茶的水浸液在浓度24mg/mL对金黄色葡萄球菌均有抑菌作用;在浓度48mg/mL对大肠杆菌均有抑菌作用,且浓度越高,抑制作用越强;绿茶、乌龙茶、黄茶、白茶水浸液在低于饮用浓度(6mg/mL)对金黄色葡萄球菌仍有抑菌作用;六大茶类中,以绿茶水浸液的抑菌效果最好,红茶的最差,黄茶、白茶的抑菌效果优于黑茶和红茶。说明六大茶类对肠道致病菌均有抑菌效果,抑菌效果与其内含成分有关。      

Effects of potassium and magnesium nutrition on the quality components of different types of tea

In field experiments, the effects of potassium and magnesium nutrition on the quality components of different types of tea, including black tea, oolong tea and green tea, were studied. The results show that K and Mg fertilizer application increased the contents of free amino acids and caffeine of the various tea types with the maximum increase found in the treatment including both nutrients. The content of polyphenols in tea leaves was also increased by K application. The effect of Mg on polyphenol content was inconsistent. In general, Mg apparently decreased the content of polyphenols and only in case the soils were depleted of plant available K and Mg, a slight increase could be observed. The contents of theaflavins and thearubigins, important quality components of brewed black tea, were also increased by K application. Flavour compounds in brewed oolong tea were considerably improved by K and Mg application. © 1999 Society of Chemical Industry     

Overview of antibacterial, antitoxin, antiviral, and antifungal activities of tea flavonoids and teas

Tea leaves produce organic compounds that may be involved in the defense of the plants against invading pathogens including insects, bacteria, fungi, and viruses. These metabolites include polyphenolic compounds, the six so-called catechins, and the methyl-xanthine alkaloids caffeine, theobromine, and theophylline. Postharvest inactivation of phenol oxidases in green tea leaves prevents oxidation of the catechins, whereas postharvest enzyme-catalyzed oxidation (fermentation) of catechins in tea leaves results in the formation of four theaflavins as well as polymeric thearubigins. These substances impart the black color to black teas. Black and partly fermented oolong teas contain both classes of phenolic compounds. A need exists to develop a better understanding of the roles of polyphenolic tea compounds in food and medical microbiology. This overview surveys and interprets our present knowledge of activities of tea flavonoids and teas against foodborne and other pathogenic bacteria, virulent protein toxins produced by some of the bacteria, virulent bacteriophages, pathogenic viruses and fungi. Also covered are synergistic, mechanistic, and bioavailability aspects of the antimicrobial effects. Further research is suggested for each of these categories. The herein described findings are not only of fundamental interest, but also have practical implications for nutrition, food safety, and animal and human health.     

信阳产地不同茶类抗氧化活性的研究

目的 探讨信阳产地传统茶(信阳毛尖1、2和信阳红1、2)与新试制茶(奇岩、奇白和奇红)的抗氧化活性。方法 通过高效液相色谱仪和紫外分光光度计检测7种茶中6种儿茶素单体、茶多酚等13个指标;然后利用1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)法和糖尿病小鼠模型检测这些茶的体外和体内抗氧化活性。结果 不同茶中所含主要抗氧化成分含量及组成存在差异,受茶树品种、鲜叶采摘标准、季节和制作工艺等因素综合影响。通过计算7种茶清除DPPH自由基的半抑制浓度(half maximal inhibitory concentration, IC₅₀)值,得出抗氧化强弱为绿茶>乌龙茶>白茶>红茶。相关性分析, IC₅₀值与茶多酚、维生素C、儿茶素总量及其6个单体成显著负相关(P<0.05、P<0.01),与黄酮和没食子酸成极显著正相关(P<0.01)。体内抗氧化检测10个处理中,信阳毛尖2处理丙二醛(malonaldehyde, MDA)最低,信阳红2处理MDA最高。信阳毛...     

Chemoprevention of lung cancer by tea

Tea is the second only to water as the most consumed beverage in the world. Both green and black teas have been studied for their health benefits for a variety of diseases, particularly cancer. Lung cancer is the predominant cause of cancer mortality in developed countries. Smokers' risk of lung cancer is 20 times that of persons who have never smoked. Epidemiological studies on the cancer-preventive effects of tea produce inconsistent results, which could in part be attributed to the lack of a universal standard for tea preparations. However, most animal studies indicate that tea has strong chemopreventive effects against lung tumorigenesis. The reported mechanisms for chemopreventive activity of green tea are antioxidation, induction of phase II enzymes, inhibition of TNFalpha expression and release, inhibition of cell proliferation, and induction of apoptosis. Cell cycle arrest and apoptosis induced by green tea are probably the two most significant factors. Future studies are needed to determine how green tea affects the genes associated with cell cycle regulation and apoptosis during the mouse lung carcinogenesis process.     

On-line high-performance liquid chromatography analysis of the antioxidant activity of phenolic compounds in green and black tea

Teas represent a rich source of dietary antioxidants. This paper describes analysis of the antioxidant potential of individual tea phenolics using an on-line high-performance liquid chromatography (HPLC) method. Tea phenolics from Kenyan green and black teas were identified using liquid chromatography--mass spectrometry (LC-MS(n)) in conjunction with the analysis of their 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS+) radical scavenging ability. Antioxidant potential of flavan-3-ols, caffeoylquinic acids, flavonols, and theaflavins was assessed in comparison to the synthetic vitamin E analogue Trolox. (-)-Epigallocatechin gallate was identified as the most potent antioxidant with a Trolox equivalent antioxidant capacity (TEAC) value of 3.0, contributing approximately 30% of the total antioxidant capacity of green tea. Theaflavins retained antioxidant capacity similar to that of (-)-epicatechin monomers whilst conjugated flavonols did not contribute significantly to the antioxidant capacity of either green or black tea. After HPLC analysis of the antioxidant capacity of phenolics in black tea some 80% of antioxidant activity remained unaccounted for indicating the potential importance of thearubigens as antioxidants in black teas.     

Comparison of the antioxidant capacity and the antimicrobial activity of black and green tea

Tea is a common beverage. The green tea is preferentially recommended for its strong antioxidant properties and also for its antimicrobial activity. The antioxidant capacities of 30 samples (black and green tea) were determined by the chemiluminescent Trolox equivalent antioxidant capacity (TEAC) determination. The average value of TEAC of the non-fermented (green tea) and semi-fermented tea samples was 1.43 mM and the average value of TEAC of the fermented teas (black tea) samples was 1.43 mM. All samples were stored in freezer (?20 °C) and the TEAC determination was repeated after a year. The average values of TEAC of non-fermented and semi-fermented tea samples were twofold lower in comparison to fermented tea samples and only 20% of average value of TEAC of the fresh tea infusion. The parallel determinations of minimal inhibitory concentration (MIC) on gram-positive and gram-negative bacterial strains (Enterococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli) were done. Also the MIC was possible to determine after a year. The assumed prevailing antioxidant and antimicrobial activities of non-fermented tea infusions were not confirmed as well as the dominant antioxidant and antimicrobial properties of specific type of tea infusion.     

牛奶对茶汤纳米聚集体茶多酚分布特性的影响

茶汤纳米聚集体是茶多酚和蛋白质等自组装而成的纳米胶粒,是各组分介于游离分子与沉淀颗粒的中间状态。为探究牛奶对茶汤茶多酚分布特性的影响,本研究以云南大叶种蒸青绿茶、红茶为原料,以1:50茶水比浸提茶汤,按不同比例添加全脂、半脱脂和脱脂牛奶,利用超滤离心技术分离茶汤纳米聚集体,采用动态光散射技术分析各组茶汤纳米聚集体的总光强和平均直径,采用福林酚法分析其茶多酚浓度和分布率,比较研究牛奶添加比例、脂肪含量和茶类等因素对纳米聚集体物理化学特性和茶多酚分布特性的影响。结果表明:添加不同脂肪含量的牛奶均会促使部分牛奶纳米胶粒与茶汤纳米聚集体结合,导致茶汤超过90%的茶多酚富集于纳米聚集体,使绿茶和红茶的游离茶多酚比例分别降低78%和67%。初步证实:添加牛奶会促进绿茶、红茶的茶多酚参与分子聚集,使游离茶多酚比例大幅降低。