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Tea drinking impacts aging and aging-related diseases. However, knowledge of anti-aging molecules other than the major catechins in complex tea extracts remains limited. Here we used Caenorhabditis elegans to analyze the longevity effects of tea extracts and constituents comprehensively. We found that the hot water extract of green tea prolonged lifespan and heathspan. Further, the MeOH fraction prolonged lifespan significantly longer than other fractions. Correlation analysis between mass spectroscopic data and anti-aging activity suggests that ester-type catechins (ETCs) are the major anti-aging components, including 4 common ETCs, 6 phenylpropanoid-substituted ester-type catechins (PSECs), 5 cinnamoylated catechins (CCs), 7 ester-type flavoalkaloids (ETFs), and 4 cinnamoylated flavoalkaloids (CFs). CFs (200 μM) are the strongest anti-aging ETCs (with the longest 73% lifespan extension). Green tea hot water extracts and ETCs improved healthspan by enhancing stress resistance and reducing ROS accumulation. The mechanistic study suggests that they work by multiple pathways. Moreover, ETCs modulated gut microbial homeostasis, increased the content of short-chain fatty acids, and reduced fat content. Altogether, our study provides new evidence for the anti-aging benefits of green tea and insights into a deep understanding of the chemical truth and multi-target mechanism. • Ester-type catechins (ETCs) are the major anti-aging components in green tea. • Cinnamoylated flavoalkaloids extend lifespan >70% in C. elegans. • Lifespan extension is attributed to daf-2 , age-1, daf-16 , sir-2.1 , s kn-1 , aak-2, hsf-1, and eat-2. • ETCs improve intestinal microbes homeostasis and increase content of SCFA. [ABSTRACT FROM AUTHOR]

The high catechin content in summer-to-autumn tea leaves often results in strong, unpleasant tastes, leading to significant resource waste and economic losses due to lignification of unpicked leaves. This study aims to improve the taste quality of summer-to-autumn green teas by combining fine manipulation techniques with hyperspectral observation. Fine manipulation notably enhanced infusion taste quality, particularly in astringency and its aftertaste (aftertasteA). Using Partial Least Squares Discriminant Analysis (PLSDA) on hyperspectral data, 100% prediction accuracy was achieved for dry tea appearance in the near-infrared spectrum. Astringency and aftertasteA correlated with hyperspectral data, allowing precise estimation with over 90% accuracy in both visible and near-infrared spectrums. Epicatechin gallate (ECG) emerged as a key taste compound, enabling non-invasive taste prediction. Practical applications in processing and quality control are demonstrated by the derived equations (Astringency = −0.88 × ECG + 45.401, AftertasteA = −0.353 × ECG + 18.609), highlighting ECG's role in shaping green tea taste profiles. [Display omitted] • Fine-manipulation enhances green tea taste quality from summer-to-autumn leaves. • Near-infrared hyperspectral imaging achieves 100% accuracy in process distinction. • The hyperspectral observation facilitates the estimation of infusion taste. • ECG emerges as a critical compound linking tea appearance to infusion taste. • Astringency = −0.88 × ECG (μg/mL) + 45.401, AftertasteA = −0.353 × ECG (μg/mL) + 18.609. [ABSTRACT FROM AUTHOR]

Kombucha was fermented by the pure cultured tea fungus, and the changes of functional compounds and their transformation were explored. After fermentation, the contents of total polyphenols, total flavonoids, quercetin, kaempferol and catechins respectively enhanced by 77.14%, 69.23%, 89.11%, 70.32% and 45.77% compared with the control, while flavonol glycosides reduced by 38.98%. The bioavailability of polyphenols and flavonoids respectively increased by 29.52% and 740.6%, and DPPH and ABTS respectively increased by 43.81% and 35.08% compared with the control. Correlation analysis showed that microorganisms and the antioxidant activity were highly positive correlation with total polyphenols, total flavonoids, EGC, EC, EGCG, ECG, quercetin and kaempferol, and negative correlation with kaempferol-3-glucoside. The constructed models confirmed that organic acids were more likely to damage the structure of tea leaves, and enzymes (polygalacturonidase and tannase) and solvents (acids, alcohols and esters) had a synergistic effect on the biotransformation of functional compounds. Graphical abstract [Display omitted] • Improving the contents of main functional compounds in kombucha by the tea fungus • Increasing the bioavailability of total polyphenols and total flavonoids in kombucha • Revealing the relationship of the compounds with antioxidant activity and tea fungus • Exploring the biotransformation mechanism of polyphenols and flavonoids [ABSTRACT FROM AUTHOR]

• Steamed green tea had higher concentrations of sucrose and free amino acids. • Steaming retained more compounds associated with sweet and fresh tastes, such as free amino acids. • Frying produced more compounds with bitter tastes, such as catechin. Fixation is a crucial step in green tea processing that can impact quality. In this study, we explored the differences in the chemical components of steamed and fried green teas made from the same batch of fresh tea leaves using different fixing methods. Results showed that concentrations of sucrose and free amino acids were significantly higher in steamed green tea. Abundances of 12 compounds including purine nucleoside, pyrimidine nucleoside derivatives, and catechins were higher in fried green tea, while 34 compounds such as amino acids and their derivatives, benzofurans and flavonoids were higher in steamed green tea. Thus, steaming retained more compounds associated with sweet and fresh tastes, such as free amino acids, while frying produced more compounds with bitter tastes, such as catechin. This might explain why steamed green tea is mellower than fried tea. [ABSTRACT FROM AUTHOR]

[Display omitted] • The first electroanalytical method for the estimation of total phenolic and alkaloid contents in tea samples. • The method utilized catechin and caffeine oxidation signals. • A boron-doped diamond electrode was employed. • Through the analysis of black and green tea samples, the applicability was demonstrated. This work outlines the simultaneous estimation of the total phenolic and alkaloid contents in the tea samples by using catechin (C) and caffeine (CAF) oxidation signals at a non-modified boron-doped diamond (BDD) electrode. Two irreversible oxidation peaks, about + 1.03 (for C) and + 1.45 V (for CAF) vs Ag/AgCl in acetate buffer solution at pH 4.7, were seen in the cyclic voltammetric profile of the binary mixtures of C and CAF. In optimal conditions and utilizing the square-wave mode, the BDD electrode allows for simultaneous quantification of C and CAF within the concentration ranges of 5.0–100.0 µg mL−1 (1.72 × 10-5 − 3.45 × 10-3 mol/L) and 1.0–50.0 µg mL−1 (5.15 × 10-6 − 2.57 × 10-4 mol/L) respectively. The corresponding detection limits are 1.22 µg mL−1 (4.21 × 10-6 mol/L) for C and 0.11 µg mL−1 (5.66 × 10-7 mol/L) for CAF. Other phenolic compounds (like tannic acid, gallic acid, epicatechin, and epigallocatechin gallate) and other alkaloids (theophylline and theobromine) present in tea samples were examined for selectivity assessment. Ultimately, the applicability of the proposed approach was demonstrated by estimating the total phenolic and alkaloid contents in the black and green tea samples, expressed as C and CAF equivalents. The results obtained were contrasted against those acquired using UV–Vis spectrometry. [ABSTRACT FROM AUTHOR]

• 124 volatile compounds during the storage of organic green tea by SDE-GC–MS were identified. • Variations of volatile compounds in organic green tea during storage (1–16 years) were explored. • Key volatile compounds related to the storage years were screened. • The content of six volatile compounds showed good predictive ability for the storage years. In the present study, the volatile compounds in organic green tea with a continuous storage period (ranging from 1 to 16 years) were comprehensively analyzed and compared through SDE-GC–MS and chemometrics. The results revealed that the total of 124 volatiles were identified, and their total amount was increased with the prolongation of the storage years. Ketones, alcohols, esters, and aromatic hydrocarbons were the main types of volatiles in organic green tea, among which 26 volatile compounds were significantly correlated with storage years, and six volatile compounds that were most seriously affected by the storage years. The results of the support vector machine classification combined with multiple linear regression analysis showed that the content-period prediction model for the six volatile compounds can accurately predict the storage years of organic green tea. Therefore, this study offers novel insights into volatile compounds changes during the storage of green tea. [ABSTRACT FROM AUTHOR]

• Six tea categories could be distinguished based on differences in compound accumulation. • Fermentation significantly reduced total polyphenols, catechins, and theanine content in tea. • The amounts of compounds in tea samples were closely related to the geographical origins. • Amino acids in green tea accumulate more in spring, while polyphenols more in summer and autumn. The processing techniques, geographical origins, and harvesting seasons have a significant impact on tea compound accumulation, leading to different flavor characteristics and consumer preferences for tea. Herein, six categories of tea involving 1329 samples revealed the distribution characteristics via compound accumulation, as well as the impact of production regions and harvesting seasons on flavor chemicals. With the increasing fermentation degree, the average content of tea polyphenols, catechins, and theanine in dark tea decreased by 57.78%, 94.64%, and 98.57% compared to green tea, respectively. The compounds in tea fluctuate with the geographical origins and seasons, with theanine and free amino acids being more accumulated in the Jiangnan tea region in spring tea, while total polyphenols and catechins were more abundant in Southwest China's tea region in summer and autumn tea. This study comprehensively understands the accumulation characteristics of tea compounds corresponding to processing techniques and the geographical origins of Chinese tea. [ABSTRACT FROM AUTHOR]

Highlights • Roasting of green tea decrease astringency by catechin oligomerization. • Spectroscopic studies suggested the presence of sugar units in the oligomers. • Model experiments using 13C-labeled glucose confirmed the participation of sugars. • Model experiments were performed using tea catechin and phloroglucinol. • Reactions of carbonyl groups with catechin A-rings causes the oligomerization. Abstract Roasting of green tea causes oligomerization of tea catechins, which decreases the astringency. The aim of this study was to elucidate the oligomerization mechanism. The 13C NMR spectrum of the oligomer fraction showed signals arising from catechin and sugar residues. Heating of epigallocatechin-3- O -gallate with 13C-labeled glucose (150 °C for 2 h) suggested that condensation of sugars with catechin A-rings caused the oligomerization. The dimeric product obtained by heating for a shorter period (30 min) suggested cross-linking occurred between sugars and catechin A-rings. Furthermore, heating of phloroglucinol, a catechin A-ring mimic, with glucose, methylglyoxal, and dihydroxyacetone, confirmed that the basic mechanism included reaction of the catechin A-ring methine carbons with carbonyl carbons of glucose and their pyrolysis products. [ABSTRACT FROM AUTHOR]

Bitterness and astringency are two important quality attributes of green tea infusion, and catechins are the main contributor to the bitterness and astringency. The aim of this work was to quantitatively analyse the bitterness and astringency of green tea infusion according to the concentrations of catechins. The concentration–taste curves of catechins showed a pattern that fit the cubic functions, and their R 2 values were higher than 0.956. The bitterness of green tea was highly correlated with the concentrations of (−)-epigallocatechin gallate and (−)-epicatechin gallate (ECG) ( R 2  = 0.7769, p  < 0.01), and the astringency ( R 2  = 0.7878, p  < 0.01) was highly correlated with the concentrations of ECG and flavonol glycosides (myricetin 3- O -galactoside and quercetin-3- O -rutinoside). Taste interactions between different catechins and between catechins and other substances were determined. These results may enhance the understanding of tea chemistry for improving the taste of products from green tea. [ABSTRACT FROM AUTHOR]

There are eight most abundant green tea catechins (GTCs) existing in four pairs of eipimers, and carbon-3 configuration represents the only steric difference within each pair. This study aimed to use a new kinetic approach to elucidate the effect of stereochemical changes on the antioxidant activity. A mixture of eight GTCs was treated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) prepared in a series of concentrations, their relative reaction rates towards scavenging DPPH were revealed by the recently introduced parameter, i.e. D m . The 3- R configuration in (−)-epicatechin, (−)-epigallocatechin and (−)-epigallocatechin gallate gave lower D m values demonstrating faster kinetics as opposed to their 3- S counterparts, with the only exception of the pair of (−)-catechin gallate and (−)-epicatechin gallate in which 3- S configuration was faster. These results suggested that the kinetic approach adopted in this study could reflect the different antioxidant activity of GTCs attributed by minor steric changes. [ABSTRACT FROM AUTHOR]

This is the first study to investigate the extent of reduction in acrylamide formation during baking with the addition of (−)-epigallocatechin gallate (EGCG) extracted from green tea, and to determine whether EGCG influences the texture and colour attributes of bread, or interacts with other ingredients. EGCG powders were added to white bread formulations at the concentrations of 3.3, 6.6 and 9.9 g·kg −1 . The amount of acrylamide in the bread was analysed using liquid chromatography-mass spectrometry. EGCG addition significantly reduced the acrylamide formation by 37% compared to the control and decreased the moisture content of the bread by 6%. It did not affect its texture attribute, but increased the lightness and the yellowness and decreased the redness of bread crust (with contrasting results in crumb). It also decreased granule size and porosity. In conclusion, EGCG fortification is a feasible method to decrease acrylamide formation in baked bread. [ABSTRACT FROM AUTHOR]

The degradation of catechins and other phenolics in green tea infusions were monitored using fast HPLC/MS separation. The final separation was performed within 2.5 min using Ascentis Express C18 column (50 mm × 2.1 mm i.d.) packed with 2 μm porous shell particles. Degradation was studied in relation to the temperature of water (70, 80, 90 °C) and the standing time of the infusion (up to 6 h). Along with chromatographic separation, the antioxidant properties of the infusions were monitored using two spectrophotometric methods. During staying of green tea infusion, the degradation of some catechins probably to gallic acid was observed. Finally, the influence of tea bag storage on antioxidant properties of green tea was evaluated. Rapid degradation of antioxidants after 3 weeks was observed. The principal component analysis, factor analysis and discriminant analysis were used for the statistical evaluation of obtained experimental data. [ABSTRACT FROM AUTHOR]

The levels of N ε -(carboxymethyl)lysine (CML) and N ε -(carboxyethyl)lysine (CEL) in 99 tea samples from 14 geographic regions, including 44 green, 7 oolong, 41 black, and 7 dark teas were determined by liquid chromatography-tandem mass spectrometry (LC–MS/MS). The CML and CEL contents varied from 11.0 to 1701 μg/g tea and 4.6 to 133 μg/g tea, respectively. Dark tea presented the highest levels of CML and CEL, whereas green and oolong teas presented the lowest levels. Five kinds of catechins in the tea were also analyzed, and spearman’s correlation coefficients showed that all the catechins negatively correlated with CML and CEL. The results suggested that withering, fermentation and pile fermentation may facilitate the formation of CML and CEL. Catechins might inhibit the formation of CML and CEL, but their inhibitory effects may be affected by tea processing. The results of this study are useful for the production of healthier tea. [ABSTRACT FROM AUTHOR]

Major green tea catechin, epigallocatechin-3-gallate (EGCG), binds non-covalently to numerous dietary proteins, including beta-lactoglobulin of cow’s milk. The effects of glycation of proteins via Maillard reaction on the binding capacity for polyphenols and the antiradical properties of the formed complexes have not been studied previously. Binding constant of BLG glycated by milk sugar lactose to EGCG was measured by the method of fluorophore quenching. Binding of EGCG was confirmed by CD and FTIR. The antioxidative properties of the complexes were examined by measuring ABTS radical scavenging capacity, superoxide anion scavenging capacity and total reducing power assay. Glycation of BLG does not significantly influence the binding constant of EGCG for the protein. Conformational changes were observed for both native and glycated BLG upon complexation with EGCG. Masking effect of polyphenol complexation on the antioxidative potential of the protein was of the similar degree for both glycated BLG and native BLG. [ABSTRACT FROM AUTHOR]

Molecular integrations between green tea catechins and milk fat globules in a cheese matrix were investigated using solid-state magic angle spinning nuclear magnetic resonance spectroscopy. Full-fat cheeses were manufactured containing free catechin or free green tea extract (GTE), and liposomal encapsulated catechin or liposomal encapsulated GTE. Molecular mobility of the carbon species in the cheeses was measured by a wide-line separation technique. The 1 H evolution frequency profile of the 13 C peak at 16 ppm obtained for the control cheese and cheeses containing encapsulated polyphenols (catechin or GTE) were similar, however, the spectrum was narrower for cheeses containing free polyphenols. Differences in spectral width indicates changes in the molecular mobility of –-CH 3 – or –C–C–PO 4 – species through hydrophobic and/or cation–π associations between green tea catechins and cheese fat components. However, the similar spectral profile suggests that encapsulation protects cheese fat from interaction with catechins. [ABSTRACT FROM AUTHOR]

Flavour determinants in tea infusions and their changes during manufacturing processes were studied using Camellia sinensis cultivars ‘Bai-Sang Cha’ (‘BAS’) possessing significant floral scents and ‘Fuding-Dabai Cha’ (‘FUD’) with common green tea odour. Metabolite profiling based on odour activity threshold revealed that ‘BAS’ contained higher levels of the active odorants β-ionone, linalool and its two oxides, geraniol, epoxylinalool, decanal and taste determinant catechins than ‘FUD’ ( p < 0.05). Enhanced transcription of some terpenoid and catechin biosynthetic genes in ‘BAS’ suggested genetically enhanced production of those flavour compounds. Due to manufacturing processes, the levels of linalool and geraniol decreased whereas those of β-ionone, linalool oxides, indole and cis -jasmone increased. Compared with pan-fire treatment, steam treatment reduced the levels of catechins and proportion of geraniol, linalool and its derivatives, consequently, reducing catechin-related astringency and monoterpenol-related floral scent. Our study suggests that flavour determinant targeted modulation could be made through genotype and manufacturing improvements. [ABSTRACT FROM AUTHOR]

The determination of putative chemical interactions between the milk fat globule membrane and green tea catechins provided useful information about the role of milk fat globules (MFGs) in high-fat dairy systems, such as cheese, and containing bioactive compounds, such as tea catechins. Catechins from green tea (125–1000 ppm), including (+)-catechin, (−)-epigallocatechin gallate, and green tea extract were added to washed MFGs to examine possible interactions. The addition of catechins gave a significant change in the size and ζ-potential of MFGs. The recovery of different catechins from the milk fat globule suspensions was found to vary, suggesting selective association with the milk fat globule membranes. The interactions were further investigated using transmission electron microscopy and Fourier transform infra-red spectroscopy. It is suggested that catechins are localised in association with milk fat globule membrane domains as they contain both hydrophobic and hydrophilic moieties with potential points of molecular interaction. [ABSTRACT FROM AUTHOR]

Transformation from green tea leaves into black tea involves oxidation of catechins into theaflavins and other complex phenolics by endogenous enzymes in tea leaves. By employing tyrosinase and laccase, both from Agaricus bisporus , on green tea catechins, the oxidation process was directed towards a higher theaflavins content, which is considered an important quality parameter in tea. The main tea catechins were incubated with tyrosinase and laccase, and product formation was monitored by RP-UHPLC–PDA-ESI-MS. The kind of catechin, their substitution with a galloyl group, and the type of oxidase used were important factors determining theaflavin concentrations. In particular, incubation of epicatechin with epigallocatechin with tyrosinase gave a high, stable theaflavin content. In a green tea extract, tyrosinase increased the proportion of theaflavins by twofold compared to black tea. Laccase mainly formed insoluble complexes. Our results indicate that the phenolic profile of tea can be modulated by using commercially available exogenous oxidases. [ABSTRACT FROM AUTHOR]

A novel paper-based Nanoceria Reducing Antioxidant Capacity (NanoCerac) assay for antioxidant detection (Sharpe, Frasco, Andreescu, & Andreescu, 2012), has been adapted for the first time as a high-throughput method, in order to measure the effect of brewing conditions and re-infusion on the antioxidant capacity of twenty-four commercial green teas. The oxygen radical absorbance capacity (ORAC) assay, frequently applied to complex foods and beverages, was used as a comparator measure of antioxidant capacity. A novel measure of sustained antioxidant capacity, the total inherent antioxidant capacity (TI-NanoCerac and TI-ORAC) was measured by infusing each tea six times. Effects of brewing conditions (temperature, brew time, etc.) were assessed using one popular tea as a standard. Both NanoCerac and ORAC assays correlated moderately ( R 2 0.80 ± 0.19). The average first-brew NanoCerac, TI-NanoCerac, first-brew ORAC and TI-ORAC were: 0.73 ± 0.1 GAE/g tea; 2.4 ± 0.70 mmol GAE/g tea; 1.0 ± 0.3 mmol TE/g tea and 2.1 ± 0.71 mmol TE/g tea respectively. Brewing conditions including water temperature and infusion time significantly affected antioxidant capacity. The high-throughput adaptation of the original NanoCerac assay tested here offered advantages over ORAC, including portability and rapid analysis. [ABSTRACT FROM AUTHOR]

Green tea catechins are potent inhibitors of enzymes for carbohydrate digestion. However, the potential of developing low glycaemic index bakery food using green tea extract has not been investigated. Results of this study showed that addition of green tea extract (GTE) at 0.45%, 1%, and 2% concentration levels significantly reduced the glycaemic potential of baked and steamed bread. The average retention levels of catechins in the baked and steamed bread were 75.3–89.5% and 81.4–99.3%, respectively. Bread fortified with 2% GTE showed a significantly lower level of glucose release during the first 90 min of pancreatic digestion as well as a lower content of rapidly digested starch (RDS) content. A significantly negative correlation was found between the catechin retention level and the RDS content of bread. The potential of transforming bread into a low GI food using GTE fortification was proven to be promising. [ABSTRACT FROM AUTHOR]

Tea cream is prevalent in various types of tea, yet a comparison of the mechanism of creaming in different teas remains uncertain. Here, we compared physicochemical characteristics, phytochemical composition, and simulated digestive profiles of green tea and black tea cream, looking to exploit their concentration and structure based mechanisms and in vitro bioaccessibility. Green tea cream particles were roughly one order of magnitude larger than those of black tea in size. Moreover, creaming concentrations of catechins, proteins and methylxanthines of green tea were dramatically higher than black tea. As major creaming components, gallated catechins, theaflavins, thearubigins, theabrownines, proteins and methylxanthines also exhibited high creaming affinities. Green tea cream particles, which were completely destroyed by simulated digestion, had few impacts on digestive recoveries of catechins and methylxanthines. In comparison, black tea cream particles were more stable under mimicking digestion, and clarification remarkably decreased the in vitro bioaccessibility of catechins and methylxanthines. [ABSTRACT FROM AUTHOR]

• Epicatechins were all significantly lost during OP. • Non-galloylated catechins were lost through dimerization and epimerization. • Galloylated catechins were lost through hydrolysis, complexation, or dimerization. • EGCG was the least stable of the epicatechins, whereas EC the most. • EGCG was susceptible to pH condition, mucin, and esterase, in human oral cavity. Oral processing (OP), referring to the whole process of food digestion in human mouth, has a major influence on food flavor perception. This study focused on the compositional changes of the four green tea epicatechins (viz., EC, EGC, ECG, EGCG) during OP, based on targeted and nontargeted metabolomics. It was found that the four epicatechins were all extensively lost through transformation undergoing OP, among which EC was the most stable one, whereas EGCG the least. EGCG was further revealed to be susceptible to human oral cavity in the simulated OP in vitro. It could be converted physically by precipitating with mucin in saliva, and chemically through hydrolysis and dimerization, mediated mainly by the neutral pH condition. The OP of epicatechins also caused salivary composition changes possibly involving health benefits of green tea. These findings could raise awareness of the interactions between epicatechins, or any other food materials, with human mouth. [ABSTRACT FROM AUTHOR]

Highlights: [•] NIRS was used to determine caffeine and nine catechins in tea leaves. [•] Reference contents of caffeine and nine catechins were determined by RP-HPLC-DAD. [•] Average contents of caffeine and total catechins were 16.8 and 88.4mg/g of the whole data set. [•] Determination of caffeine, EGC, C, EGCG, EC, ECG, and total catechins can be predicted with reliable accuracy using NIRS. [ABSTRACT FROM AUTHOR]

Highlights: [•] Green tea antioxidants were efficiently trapped within liposomes in cheese. [•] Encapsulation efficiency of green tea antioxidants within liposomes was high. [•] Adding green tea catechins elevated the phase transition of liposomes to >50°C. [ABSTRACT FROM AUTHOR]

Highlights: [•] Application of SPE and LLE for sample clean-up and enrichment of EGCG. [•] A stability and purity-indicating analysis protocol for EGCG in nutraceutical preparations. [•] The use of gallic acid as an internal standard to overcome the scarcity of EGCG standard. [•] A validated, stability-indicating TLC densitometric assay for analysis of EGCG. [ABSTRACT FROM AUTHOR]

Highlights: [•] Development of a rapid HPLC procedure based on the use of monolithic column. [•] The use of microwave assisted extraction for the isolation of the catechin compounds. [•] Application of the methods for the determination of catechins in various types of teas. [ABSTRACT FROM AUTHOR]

Highlights: [•] Catechins have effects based on preclinical and clinical trials studies. [•] Catechins exhibit both pro- and antioxidant activities. [•] Catechins multiple uses in cancer therapy. [•] Catechins are involved in alternative splicing. [Copyright &y& Elsevier]

• This study is to non-destructively estimate catechin concentrations in green tea shoots using spectral imagery. • Hyperspectral image sensor is used to extract the spectral attributes of green tea shoots. • Catechin concentrations grown in commercial or organic fertilizers are estimated. • The possibility of developing a year-invariant model is presented with mutual prediction. • The direction for model improvement is proposed by comparing the weights of variables. Hyperspectral imagery was applied to estimating non-galloyl (EC, EGC) and galloyl (ECG, EGCG) types of catechins in new shoots of green tea. Partial least squares regression models were developed to consider the effects of commercial fertilizer (CF) and organic fertilizer (OF). The models could explain each type of catechin with a precision of more than 0.79, with a few exceptions. When the CF model was applied to the OF hyperspectral reflectance and the OF model was applied to the CF hyperspectral reflectance for mutual prediction, the prediction accuracy was better with the OF models than CF models. The prediction models using both CF and OF data (hyperspectral reflectances, and concentrations of catechins) had a precision of more than 0.76 except for the non-galloyl-type catechins as a group and EGC alone. These results provide useful data for maintaining and improving the quality of green tea. [ABSTRACT FROM AUTHOR]

• UPLC-Q-TOF/MS was developed for LC-MS metabolomics analysis in tea of Xinyang Region. • PCA, HCA and OPLS-DA could completely divide those teas into green and white tea. • 110 Relevant metabolites conduced to the identification of production season. • The Prolonged withering convert catechins and phenolic acids into theaflavins. • Kaempferol and taxifolin might contribute to DPPH scavenging ability of white tea. Contents of 20 bioactive compounds in 12 teas produced in Xinyang Region were determined by high performance liquid chromatography. Ultra-high performance liquid chromatography-quadrupole time of flight-mass spectrometry was developed for untargeted metabolomics analysis. Antioxidant activities were measured by 4 various assays. Those teas could be completely divided into green and white tea through principal component analysis, hierarchical cluster analysis and orthonormal partial least squares-discriminant analysis (R2Y = 0.996 and Q2 = 0.982, respectively). The prolonged withering generated 472 differentiated metabolites between white and green tea, prompted significant decreases (variable importance in the projection > 1.0, p-value < 0.05 and fold change > 1.50) of most catechins and 8 phenolic acids to form 4 theaflavins, and benefited for the accumulation of 17 flavonoids and flavonoid glycosides, 8 flavanone and their derivatives, 20 free amino acids, 12 sugars and 1 purine alkaloid. Additionally, kaempferol and taxifolin contributed to 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging ability of white tea. [ABSTRACT FROM AUTHOR]

Abstract: Green tea seems to have a positive impact on health due to the catechins-found as flavanols. Thus, the present study was aimed to develop a low cost reversed phase high performance liquid chromatographic (HPLC) method for simultaneous determination of flavanol contents, namely catechin (C), epicatechin (EC), epigallocatechin (EGC), epicatechin 3-gallate (ECG) and epigallocatechin 3-gallate (EGCG) and caffeine in 29 commercial green tea samples available in a Saudi Arabian local market. A C-18 reversed-phase column, acetonitrile–trifluoroacetic acid as a mobile phase, coupled with UV detector at 205nm, was successfully used for precise analysis of the tested analytes in boiled water of digested tea leaves. The average values of N (No. of theoretical plates), HETP (height equivalent of theoretical plates) and R s (separation factor) (at 10μgml−1 of the catechins EC, EGC, EGCG and ECG) were 2.6×103 ±1.2×103, 1.7×10−3 ±4.7×10−4 cm and 1.7±5.53×10−2, respectively. The developed HPLC method demonstrated excellent performance, with low limits of detection (LOD) and quantification (LOQ) of the tested catechins of 0.004–0.05μgml−1 and 0.01–0.17μgml−1, respectively, and recovery percentages of 96–101%. The influence of infusion time (5–30min) and temperature on the content of the flavanols was investigated by HPLC. After a 5min infusion of the tea leaves, the average concentrations of caffeine, catechin, EC, EGC, ECG and EGCG were found to be in the ranges 0.086–2.23, 0.113–2.94, 0.58–10.22, 0.19–24.9, 0.22–13.9 and 1.01–43.3mgg−1, respectively. The contents of caffeine and catechins followed the sequence: EGCG>EGC>ECG>EC>C>caffeine. The method was applied satisfactorily for the analysis of (+)-catechin, even at trace and ultra trace concentrations of catechins. The method was rapid, accurate, reproducible and ideal for routine analysis. [Copyright &y& Elsevier]

Abstract: Green tea (Camellia sinensis) is one of the most widely consumed beverages in the world. The cancer chemopreventive qualities of green tea have been well documented. Epigallocatechin gallate (EGCG) is often described as the most potently chemopreventive green tea catechin; however, the low bioavailability of EGCG is a limiting factor for its biological effect. Thus, the aim of this work was to test the chemopreventive potential of green tea extract and EGCG after tannase-mediated hydrolysis. The results showed that the biotransformed compounds retained most of the beneficial properties of the original compounds, and some beneficial properties were improved in the biotransformed compounds. Biotransformation of EGCG decreased its toxicity without affecting its antiproliferative effects. Furthermore, human cells gene expression profiling showed that the biotransformed compounds modulated the expression of several genes related to carcinogenesis. These results demonstrate the benefits of the biotechnological modification of natural food molecules, allowing the improvement of the nutraceutical potential of a beverage as green tea. [Copyright &y& Elsevier]

Abstract: The variations in the contents of catechins and purine alkaloids in relation to the chlorophyll contents in albino tea cultivar ‘Anji baicha’ and normal cultivar ‘Longjing 43’, grown in Anji and Guilin, were determined. The results showed that, compared to ‘Anji baicha’, ‘Longjing 43’ had significantly higher (−)-epigallocatechin (EGC), (−)-epicatechin (EC), (−)-epicatechin gallate (ECG), theobromine and caffeine contents in Anji, and significantly higher (+)-catechin (C), ECG and caffeine contents in Guilin. ‘Anji baicha’ only had C content significantly higher than ‘Longjing 43’ in Anji. Correlation analysis indicated that C, EGC and (−)-epigallocatechin gallate (EGCG) were significantly and negatively correlated with chlorophyll contents, suggesting that chlorophylls might play vital roles in the regulation of catechin biosynthesis. Moreover, no significant correlation was observed between purine alkaloids and chlorophylls, indicating that the biosynthesis of purine alkaloids might be affected by genotypic factors other than chlorophyll biosynthesis. [Copyright &y& Elsevier]

Abstract: A sulfated-β-cyclodextrin (s-β-CD) modified reduced flow micellar electrokinetic chromatography (RF-MEKC) method was developed and validated for the determination of catechins in green tea. The optimal electrolyte consisted of 0.2% triethylamine, 50mmol/L SDS and 0.8% s-β-CD (pH=2.9), allowing baseline separation of five catechins in 4min. The samples and standards were injected at 0.6psi for 5s under constant voltage of −30kV. Sample preparation simply involved extraction of 2g of tea with 200mL water at 95°C under constant stirring for 5min. The method demonstrated excellent performance, with limits of detection (LOD) and quantification (LOQ) of 0.02–0.1 and 0.1–0.5μg/mL, respectively, and recovery percentages of 94–101%. The method was applied to six samples of Brazilian green tea infusions. Epigallocatechin gallate (23.4–112.4μg/mL) was the major component, followed by epigallocatechin (18.4–78.9μg/mL), epicatechin gallate (5.6–29.6μg/mL), epicatechin (4.6–14.5μg/mL) and catechin (3.2–8.2μg/mL). [Copyright &y& Elsevier]

Abstract: Eight green and three black teas have been analysed using square-wave voltammetry at a glassy-carbon electrode, at pH 2 and square-wave frequency 100Hz. The SWV response of teas consisted of two partially resolved anodic peaks: peak 1 at around 0.372V, and peak 2 around 0.491V. First anodic peak was due to oxidation of pyrogallol catechins, i.e. epigallocatechin gallate (EGCG) and epigallocatechin (EGC), and peak 2 can be associated with oxidation of ortho-hydroquinone and galloyl groups in catechins, gallic acid, theaflavins, and other catechol-type phenolics present in tea. Peak 1 has been chosen for quantification purposes, and concentrations of catechins were calculated from the calibration plot constructed for EGC used as external standard. Amounts of catechins in green teas obtained by SWV were in good agreement with those obtained using reverse-phase high-performance liquid chromatography with electrochemical detection (RP-HPLC-ECD). For black tea samples the detector response of peak 1 was diminished due to interferences of coexisting polyphenols, and SWV obtained results were something lower than those obtained by HPLC-ECD. [Copyright &y& Elsevier]

Abstract: The effect of a green tea marinade on the formation of heterocyclic aromatic amines (HAs) was examined in pan-fried beef cooked at 180–200°C for 4min each side. Different marinating times were assayed and unmarinated samples cooked in similar conditions provided reference HAs levels. A green tea marinade catechin rich was prepared taking 1g of green tea and infusing with 125ml of boiling tap water during 10min. Four HAs were quantified in unmarinated and marinated meat samples during 1, 2, 4 and 6h at 5°C. Compared with the unmarinated samples, marinating in green tea resulted in a significant decrease (p <0.05) of levels of PhIP and AαC. Person correlation indicated that the reduction of the levels of these HAs in meat marinated with the increase of marinating time was significant (respectively, r =−0.799, p <0.0001; r =−0.631, p <0.05). No reduction was observed for 4,8-DiMeIQx and MeIQx. The beef samples were tested for descriptive sensory analysis by two trained sensory panels to evaluate the influence of the green tea marinade in meat organoleptic characteristics. Analysis of results obtained through the t-test, revealed no significant differences (p <0.05) between control samples and tea marinated samples for all the thirteen attributes evaluated. [Copyright &y& Elsevier]

Abstract: The antioxidant activity of catechins isolated from green tea against peroxyl radicals, hydroxyl radicals, and peroxynitrite was determined using the total oxy-radical scavenging capacity (TOSC) assay. (−)-Epicatechin, (−)-epigallocatechin, (−)-epicatechin-3-gallate, and (−)-epigallocatechin-3-gallate were isolated and their structures were characterised based on their physical and spectral properties, and by comparison of these results with similar data in the literature. (−)-Epigallocatechin showed the highest TOSC value, and (−)-epicatechin-3-gallate was the least effective among the catechins tested. These results indicated that the presence of a gallate group at the three position plays a critical role in their antioxidant activity. However, additional insertion of a hydroxyl group at the 5′ position in the B ring attenuates the oxy-radical scavenging capacity of catechins. These results suggest that the antioxidant activity of catechins is dependent on the reactivity of both the original catechins and their products generated during reaction with oxy-radicals. [Copyright &y& Elsevier]

Abstract: Flavanoids are known to interact with proteins to form complexes whose properties depend on the structure of both the flavanoids and the protein. In this study, the fluorescent probe binding method (fluorimetry analysis) and isothermal titration calorimetry (ITC) analysis were used to characterize binding interactions of green tea (GT) flavanoids and milk proteins. The hydrophobicity of the surface sites of milk proteins was estimated using the reconstituted milk–green tea and casein–green tea systems. Reconstituted milk–green tea and casein–green tea samples were prepared with different solid-non-fat (SNF) and casein (Cn) concentrations, respectively. It was observed that the number of surface hydrophobic sites decreased in the presence of GT flavanoids for all SNF and Cn concentrations. The decrease in protein surface hydrophobicity was explained by the hydrophobic binding between milk proteins and GT flavanoids. The binding enthalpies obtained from ITC analysis implied that interaction was non-covalent between catechin and β-casein. [Copyright &y& Elsevier]

Abstract: We tested in mice the hypothesis that iron fortificants may exert oxidative activity on colon tissue homogenates (CTH), depending on the antioxidant capacity of infusions received with their diet. CTH were obtained from mice receiving daily by gavage 0.1mL of infusion (8g/100mL water) from green tea or white tea or Pelargonium purpureum or catechin (0.01g/100mL) or water (control) for five days. All CTH had higher total antioxidant capacity than the control and lower susceptibility to oxidation induced by the retentates of in vitro digests of ferrous lactate, ferrous gluconate, ferrous sulfate and NaFeEDTA. Ferrous sulfate and NaFeEDTA exhibited higher oxidative effect on CTH than ferrous gluconate or ferrous lactate. These results are in support of our hypothesis and suggest that infusions received with diet may protect the colon from a potential oxidative effect of non-absorbed iron. [Copyright &y& Elsevier]

Abstract: Green tea powder was used to substitute 0%, 10%, 20%, and 30% of wheat flour to make sponge cakes, called the control, GT10, GT20, and GT30, respectively. The viscosity and specific gravity in cake batter, and hardness, gumminess, chewiness, crumb a value, protein, total dietary fibre, ash, and various catechin content of baked cakes increased with increasing green tea levels whereas the volume, cohesiveness, adhesiveness, springiness, resilience, crust L, a, b and crumb L, b values of samples showed a reverse trend. No differences were found in all hedonic sensory results for control, GT10, and GT20 whereas GT30 were rated lower in all sensory results. Green tea cake contained a greater variety of catechins, and had good antioxidant activity, reducing power, scavenging ability on 1,1-diphenyl-2-picrylhydrazyl radicals and chelating ability on ferrous ions. Overall, green tea cake could be developed as a food with more effective antioxidant properties. [Copyright &y& Elsevier]

Abstract: The formation of green tea cream and its chemical components were investigated. The green tea infusions were processed from different parts of new shoots: the bud and the first leaf, the second leaf and its implicative stem, the third leaf and its implicative stem, and the fourth leaf and its implicative stem, which were named as first part, second part, third part and fourth part, respectively. The results showed that the formation of tea cream and its settlement slowed down gradually from the first part to the fourth part, and that the amount of tea cream also decreased accordingly. The amount of tea cream was influenced remarkably by the chemical components in the green tea infusion. The main components of green tea cream were polyphenols (29.86 –78.66%), total sugar (14.47–27.62%) and caffeine (2.35–10.43%). Catechins (12.8–42.5%) were the main components of polyphenols which participated in tea cream formation. The main components in the catechins were found to be (−)-epigallocatechin (EGC), (−)-epigallocatechin gallate (EGCG), (−)-epicatechin (EC) and (−)-epicatechin gallate (ECG). Seven minerals were found in the tea cream, including Ca2+, K+, Mg2+, Mn2+, Na+, Zn2+ and Ni2+. [Copyright &y& Elsevier]

Abstract: This paper reported the results of simultaneous analysis of main catechins (i.e., EGC, EC, EGCG and ECG) contents in green tea by the Fourier transform near infrared reflectance (FT-NIR) spectroscopy and the multivariate calibration. Partial least squares (PLS) algorithm was conducted on the calibration of regression model. The number of PLS factors and the spectral preprocessing methods were optimised simultaneously by cross-validation in the model calibration. The performance of the final model was evaluated according to root mean square error of cross-validation (RMSECV), root mean square error of prediction (RMSEP) and correlation coefficient (R). The correlations coefficients (R) in the prediction set were achieved as follows: R =0.9852 for EGC model, R =0.9596 for EC model, R = 0.9760 for EGCG model and R = 0.9763 for ECG model. This work demonstrated that NIR spectroscopy with PLS algorithm could be used to analyse main catechins contents in green tea. [Copyright &y& Elsevier]