As tea is one of the most popular beverages consumed worldwide, it is important for customers and business investigators to develop an easy and reliable method to discriminate between different types of teas from each other. A total of eighty-seven types of various white, green, oolong, black and Puer teas were collected from the major tea estates in China, and their catechin contents and volatile compounds were compared by high performance liquid chromatograph and gas chromatograph mass spectrometer. It was found green tea contained the highest concentrations of total catechins, ())-epicatechin gallate (ECG) and ())-epigallocatechin gallate (EGCG), while oolong teas contained the highest concentrations of ())-epigallocatechin (EGC) among these five types of teas. The aroma composition and their quantities in different types of teas varied quite widely. The concentration of ECG, EGCG, pentanal, hexanal, methyl jasmonate, indole, (E,E)-2,4-hexadienal and 1,2,3-trimethoxybenzene was shown to be different and could be used to discriminate white, green, oolong, black and Puer teas. The result showed that different types of teas could be partially classified by cluster analysis using index of individual catechins and volatile components.

The green tea polyphenol epigallocatechin-3-gallate (EGCG) is widely consumed as a dietary supplement. Its potential properties include slowing aging and extending lifespan, although how exactly this is achieved remains unclear. Here, we report that EGCG promoted healthy lifespan in Caenorhabditis elegans when administered throughout or only at early-to-mid adulthood. Specifically, EGCG extended lifespan in an inverted U-shaped dose-response manner. The life-extending mechanism was stimulated by EGCG-induced production of reactive oxygen species (ROS). Additionally, EGCG triggered mitochondrial biogenesis to restore mitochondrial function. The EGCG-induced increase in lifespan depends on known energy sensors such as AMPK/AAK-2, as well as SIRT1/SIR-2.1 and FOXO/DAF-16. Interestingly, aging decreased the response to EGCG and progressively neutralized its beneficial effects on longevity. Collectively, our findings link EGCG to the process of mitohormesis and suggest an inducible, AMPK/SIRT1/FOXO-dependent redox signaling module that could be invoked in different contexts to extend healthy lifespan. Its effectiveness is higher in younger adults and declines with age.

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Properties of leaf and infusion colours, chemical components and volatile flavour compounds of oolong teas and their correlation with perceived quality score given by tea-tasting panel were analysed. The scores for appearance and infused leaf correlated strongly with concentrations of chlorophyll a (chl a), chlorophyll (chl b) and chlorophyll (chl) (r = 0.355-0.433, P < 0.05) and the total quality score (TQS) positively correlated with concentrations of chl a, chl b and chl (r = 0.517-0.533, P < 0.01). The perceived taste score and TQS positively correlated with the concentration of total free amino acid (r = 0.514, 0.694, P < 0.01) and theanine (r = 0.500, 0.684, P < 0.01). The volatile composition and their quantities varied widely among oolong tea samples. Nerolidol, indole, benzeneacetaldehyde, linalool, linalool oxide I, hexanal, benzyl nitrile, geraniol and 1-penten-3-ol were prevailing volatile compounds detected in most of oolong tea samples. Principal component analysis screened ten principal components with the first three (glutamic acid, total catechins and benzeneacetaldehyde) explaining 27.86%, 20.00% and 14.46% of the total variance, respectively. Regression analysis upon the ten principal components formulated a prediction model on the total quality score with 78.5% probability. The result showed that oolong teas could be partially classified by cluster analysis based on principal components.

The present study examined the effects of black tea (Camellia sinensis) extracts (BTE) in Caenorhabditis elegans under various abiotic stressors. Results showed BTE increased nematode resistance to osmosis, heat, and UV irradiation treatments. However, BTE could not increase nematodes' lifespan under normal culture conditions and MnCl2-induced toxicity at concentrations we used. Further studies showed that BTE decreased reactive oxygen species and up-regulated some antioxidant enzymes, including GSH-PX, and genes, such as gsh-px and sod-3. However, only a slight extension in mev-1 mutants mean lifespan was observed without significance. These results indicated that the antioxidant activity of BTE might be necessary but not sufficient to protect against aging to C. elegans. Moreover, BTE increased the mRNA level of stress-response genes such as sir-2.1 and sek-1. Our finding demonstrated BTE might increase heat and UV stress resistance in a sir.2.1-dependent manner. Taken together, BTE enhanced stress resistance with multiple mechanisms in C. elegans.

Fuzhuan brick tea (FBT) is traditionally consumed by the ethnic group in the border region of northwest China. The unique yellow fungal (Eurotium cristatum) growth phase is considered to be the key process point in the manufacture of the brick tea. The fungi from FBT are not only strongly correlated to the quality of brick tea, but also have the potential function of preventing obesity. The water extract of fungi (100 μg/mL) can significantly inhibit fat deposition in 3T3-L1 adipocyte and Caenorhabditis elegans. Furthermore, the inhibition of 3T3-L1 adipocyte formation was not due to the suppression on cell viability.

The growth inhibition and cytotoxic effects of theaflavins mixture and pure theaflavins [theaflavin, theaflavins-3-gallate, theaflavins-3′-gallate and theaflavin-3, 3′-digallate] from black tea on human liver cancer HepG2 cells, gastric cancer SGC-7901 cells, lung cancer A549 cells and acute promyelocytic leukemia K562 cells were investigated. The four major theaflavins were obtained from enzymatically oxidized catechins mixture using preparative high-performance liquid chromatography (HPLC). The purity and the structures of the isolated compounds were confirmed by Journal of Food Biochemistry ISSN 1745-4514

The quality of Congou black tea fluctuates greatly with the changing seasons.However, variations in the taste quality of Congou black tea manufactured during a single spring season are far from clear. Here, we analyzed the taste quality of HuangJinCha (HJC) Congou black tea using sensory evaluation and found the taste quality of black tea manufactured in the early spring was better than that manufactured in the late spring. Principal component analysis (PCA) and cluster analysis for the data from the electronic tongue confirmed the variation and revealed that April 4 may be the critical time point at which variations in taste quality become apparent.The contents of tea polyphenols (TP), total catechins (TC), total flavones, (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate (ECG), and gallic acid (GA) showed increasing trends, whereas total amino acids (TAA) declined over time. Moreover, the variations in total amino acids (r = 0.846) and total flavones (r = -0.858) were highly significantly correlated with the average taste quality score (p < .01), suggesting these compounds were the primary factors responsible for the fluctuation in taste quality of Congou black tea processed during a single spring season. K E Y W O R D Sblack tea, electronic tongue, sensory evaluation, spring season, taste quality