Albumin causes a synergistic increase in the antioxidant activity of green tea catechins in oil-in-water emulsions

Model oil-in-water emulsions containing epicatechin (EC) and epigallocatechin gallate (EGCG) showed a synergistic increase in stability in emulsions containing added albumin. EGCG showed a stronger synergy (35%) with ovalbumin than did EC. Oxidation of the oil was monitored by determining peroxide values and hexanal contents. The effect of bovine serum albumin (BSA) on model oil-in-water emulsions containing each of the green tea catechins [epicatechin gallate (ECG), EGCG, EC and epigallocatechin (EGC)] was studied during storage at 30 °C. The green tea catechins showed moderate antioxidant activity in the emulsions with the order of activity being ECG ≈ EGCG > EC > EGC. Although BSA had very little antioxidant activity in the absence of phenolic antioxidants, the combination of BSA with each of the catechins showed strong antioxidant activity. BSA, in combination with EC, EGCG or EGC, showing the strongest antioxidant activity with good stability after 45 days storage. Model experiments with the catechins stored with BSA in aqueous solutions confirmed that protein–catechin adducts with antioxidant activity were formed between the catechins and protein. The antioxidant activity of the separated protein–catechin adducts increased strongly with storage time and was stronger for EGCG and ECG than for EC or EGC.     

H NMR-based metabolomic characterization during green tea (Camellia sinensis) fermentation

The metabolic behavior of green tea (Camellia sinensis) during tea fermentation was characterized by ¹H NMR spectroscopy coupled with multivariate statistical analysis to provide comprehensive information on changes in metabolites induced by tea fermentation. Fourteen tea metabolites of epicatechin (EC), epigallocatechin (EGC), epicatechin-3-gallate (ECG), epigallocatechin-3-gallate (EGCG), theanine, alanine, acetate, quinate, glutamate, caffeine, sucrose, glucose, and gallate, as identified by ¹H NMR spectroscopy, were responsible for metabolic differentiation between green tea and fermented tea by principal component analysis. During tea fermentation, levels of EC, EGC, ECG, EGCG, quinate, caffeine, and sucrose were decreased, whereas gallate and glucose levels were increased. In particular, unique changes in caffeine and gallate levels were observed during tea fermentation, which caffeine and gallate levels have been shown to vary after tea fermentation among many reports to date. This study highlights that metabolomics with global profiling and a highly reliable and reproducible ¹H NMR spectroscopic data set can provide a better understanding of unique changes in tea metabolites during tea fermentation.     

Common tea formulations modulate in vitro digestive recovery of green tea catechins

Epidemiological evidence suggests a role for tea catechins in reduction of chronic disease risk. However, stability of catechins under digestive conditions is poorly understood. The objective of this study was to characterize the effect of common food additives on digestive recovery of tea catechins. Green tea water extracts were formulated in beverages providing 4.5, 18, 23, and 3.5 mg per 100 mL epicatechin (EC), epigallocatechin (EGC), epigallocatechin-gallate (EGCG), and epicatechin-gallate (ECG), respectively. Common commercial beverage additives; citric acid (CA), BHT, EDTA, ascorbic acid (AA), milk (bovine, soy, and rice), and citrus juice (orange, grapefruit, lemon, and lime) were formulated into finished tea beverages at incremental dosages. Samples were then subjected to in vitro digestion simulating gastric and small intestinal conditions with pre- and post-digestion catechin profiles assessed by HPLC. Catechin stability in green tea was poor with <20% total catechins remaining post-digestion. EGC and EGCG were most sensitive with less, not double equals 10% recovery. Teas formulated with 50% bovine, soy, and rice milk increased total catechin recovery significantly to 52, 55, and 69% respectively. Including 30 mg AA in 250 mL of tea beverage significantly (p<0.05) increased catechin recovery of EGC, EGCG, EC, and ECG to 74, 54, 82, and 45% respectively. Juice preparation resulted in the highest recovery of any formulation for EGC (81-98%), EGCG (56-76%), EC (86-95%), and ECG (30-55%). These data provide evidence that tea consumption practices and formulation factors likely impact catechin digestive recovery and may result in diverse physiological profiles.     

ANTIOXIDANT PROPERTIES OF POLYPHENOLS EXTRACTED FROM GREEN AND BLACK TEAS

The catechins, including epicatechin gallate (ECG), epigallocatechin (EGC), and epigallocatechin gallate (EGCG), and the theaflavins, including theaflavin (TF), theaflavin monogallate (TF-1), and theaflavin digallate (TF-2), were extracted from green tea and black tea, respectively. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging ability, superoxide-scavenging efficiency, and lipid oxidation-inhibition ability of the pure compounds listed above as well as epicatechin (EC), carnosol, carnosic acid, and butylated hydroxytoluene (BHT) were investigated.
The DPPH radical-scavenging ability of the catechins was EGCG > ECG > EGC > EC and of the theaflavins was TF-2 > TF-1 > TF. EGCG, ECG, EGC, TF-2, TF-1, and TF showed higher DPPH radical- and superoxide-scavenging abilities than carnosol, carnosic acid, and BHT. EGCG, ECG, EGC, carnosol, and carnosic acid showed higher lipid oxidation-inhibition activity, as measured by the Rancimat method, than BHT and theaflavins.     

GREEN TEA CATECHINS AS INHIBITORS OF OXIDATION OF MEAT LIPIDS

Antioxidant activity of green tea catechins, namely, epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG) and epigallocatechin gallate (EGCG) was evaluated in a meat model system. The inhibitory effect on 2-thiobarbituric acid (TBA) values of catechins was concentration dependent, being highest at 200 mg/kg. At 200 mg/kg, the antioxidant activity of catechins as evaluated by TBA values was EGCG ≈ ECG > EGC > EC. The hexanal and pentanal contents in the headspace volatiles of meats treated with catechins at 200 mg/kg was also evaluated. These results indicated that EGCG was most active followed by ECG and EGC; EC was least effective. In comparison with α-tocopherol, catechins were generally more effective in controlling oxidation of meat lipids. Based on TBA results, butylated hydroxytoluene (BHT) was less effective, but exerted a better effect than catechins in prevention of oxidation as evidenced by the hexanal/pentanal data.     

A novel technique for chitosan microparticle preparation using a water/silicone emulsion: green tea model

Many effective methods such as spray drying, coacervation, ionic gelation, solvent evaporation and sieving have been suggested for entrapping bioactive compounds into micro‐ or nanoparticles. However, those methods still have some limitations owing to high temperature requirement, difficulty in particle harvesting or low entrapment for uncharged molecules. In this study, a novel chitosan microparticle preparation method was developed using water‐in‐silicone emulsion technique with green tea extract as a model active compound. Chitosan microparticles of diameter <5 μm were obtained from 2% chitosan solution with tripolyphosphate (TPP) solution as the hardening agent. The size and properties of the particles appeared to depend on several parameters such as TPP, emulsifier concentrations and pH. High concentration of emulsifier led to low encapsulation and particle aggregation. Entrapment efficiency of chitosan microparticles was improved with lower pH of the tripolyphosphate solution [59.94 ± 3.97 of epigallocatechin gallate (EGCG)] while slowing release of catechins. Epigallocatechin and epicatechin were released almost completely within 2 h under acidic condition whereas EGCG and epicatechin gallate were slowly released. In neutral condition, release of catechins depended on their molecular stabilities. The stabilities of catechins loaded in chitosan microparticles were varied under various temperatures. The degradation of tea catechins increased with temperature. However, the degradation of tea catechins loaded in chitosan microparticles was less than that of free catechins. Thus, the new technique for preparing chitosan microparticles containing heat‐sensitive water soluble green tea extract was successfully developed. The technique is suitable for micro‐encapsulation of hydrophilic compounds into chitosan microparticles with the ease of harvesting technique.     

SEPARATION OF INDIVIDUAL CATECHINS FROM GREEN TEA USING SILICA GEL COLUMN CHROMATOGRAPHY AND HPLC

Crude catechin mixtures from green tea were separated into six fractions using a silica gel column chromatography and a chloroform-methanol-water (65:35:10, v/v/v, lower phase) solvent system. Fraction I was free of catechins, fraction II contained epicatechin (EC), fraction III had epicatechin and epigallocatechin (EGC), fraction IV possessed EGC, fraction V contained EGC, epicatechin gallate (ECG) and epigallocatechin gallate (EGCG), and fraction VI had EGCG. EC and EGC were separated from fractions II, III and IV using HPLC with a RP-18 semipreparative column and a water-dimethylformamide-methanol-acetic acid (157:40:2:1, v/v/v/v) solvent system. For isolation of EGC, ECG and EGCG from fractions V and VI a water-acetonitrile-methanol-acetic acid (159:36:4:1, v/v/v/v) solvent system was employed. Chemical structures of purified catechins were further confirmed by ESI-MS.     

Effects of cosolvents on the decaffeination of green tea by supercritical carbon dioxide

Due to the adverse effects of the caffeine in a variety of plant products, many methods have been explored for decaffeination, in efforts to remove or reduce the caffeine contained in plant materials. In this study, in order to remove caffeine from green tea (Camellia sinensis) leaves, we have employed supercritical carbon dioxide (SC–CO₂), which is known to be an ideal solvent, coupled with a cosolvent, such as ethanol or water. By varying the extraction conditions, changes not only in the amount of caffeine, but also in the quantities of the principal bioactive components of green tea, including catechins, such as epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG) and epicatechin (EC), were determined. The extraction conditions, including temperature, pressure and the cosolvent used, were determined to affect the efficacy of caffeine and catechin extraction. In particular, the type and concentration of a cosolvent used constituted critical factors for the caffeine removal, combined with minimal loss of catechins, especially EGCG. When the dry green tea leaves were extracted with SC–CO₂ modified with 95% (v/v) ethanol at 7.0 g per 100 g of CO₂ at 300 bar and 70 °C for 120 min, the caffeine content in the decaffeinated green tea leaves was reduced to 2.6% of the initial content. However, after the SC–CO₂ extraction, a substantial loss of EGCG, as much as 37.8% of original content, proved unavoidable.     

Taste characterisation of green tea catechins

There has been interest in biological activities of green tea catechins. However, little is known about the taste characteristics of catechins. To assess the taste characteristics of catechins ((?)–epicatechin (EC), (?)–epicatechin gallate (ECg), (?)–epigallocatechin (EGC) and (?)–epigallocatechin gallate (EGCg)), sensory evaluations were performed. The taste intensity increased with increased catechins concentration. Among them, ECg showed the strongest taste. Catechins had tastes that consisted primarily of astringency and bitterness. Therefore, taste palatability decreased with increasing catechin concentrations. In line with taste intensity, taste palatability of ECg was the lowest. Taste sensor analysis and mouse behavioural assays showed same results. EC and ECg were more stable in Ringer’s solution than EGC and EGCg. Furthermore, taste cell responses to ECg that had the strong taste and better stability among catechins used were recorded. Some taste cells responded to ECg. This result suggests that ECg might be recognised by taste cells.     

Polyphenolic composition and in vitro antioxidant activities of native‐ and tannase‐treated green tea extracts

The antioxidant activities of native‐ and tannase‐treated green tea extracts along with their major polyphenol components were investigated. The polyphenolic content and composition of the tea before and after tannase treatment were determined by liquid chromatography coupled with mass spectrometry (LC‐MS). Approximately 99% of the (?)‐epigallocatechin gallate (EGCG) and (?)‐epicatechin gallate (ECG) in green tea extract were converted by tannase to (?)‐epigallocatechin (EGC) and (?)‐epicatechin (EC), respectively, after 30 min. Biotransformed green tea exhibited a significantly higher DPPH˙ radical scavenging activities than native green tea (EC₅₀ value of 0.024 ± 0.001 and 0.044 ± 0.001 mg mL^?1, respectively). Kinetic parameters such as scavenging rate and stoichiometry were calculated. The rate of DPPH˙ radical scavenging activities for tannase‐treated green tea extract was shown to be higher than native green tea extract.     

Green Tea Formulations with Vitamin C and Xylitol on Enhanced Intestinal Transport of Green Tea Catechins

The effect of green tea formulated with vitamin C and xylitol on intestinal cell transport of gallated and nongallated catechin was studied. The transport of catechins from both apical to basolateral and basolateral to apical directions was measured. The effect of vitamin C (4, 10, 20 ppm), xylitol (11, 27.5, 55 ppm), and combinations of both on the intestinal transport rate of catechins was examined. The efflux value (Pb→a/Pa→b) of (–)‐epigallocatechin (EGC), (–)‐epigallocatechin gallate (EGCG), (–)‐epicatechin (EC), and (–)‐epicatechin gallate (ECG) was 0.26, 0.22, 1.22, and 0.17, respectively, indicating that EC appeared to be less absorbed compared with other catechins. The addition of xylitol (11, 27.5, 55 ppm) and vitamin C (4, 10, 20 ppm) and in combination enhanced transport rate of nongallated catechins such as EC and EGC. For EC, vitamin C was revealed to be the most effective on intestinal transport, implying the inhibition of the efflux transport mechanism of EC. Intestinal transport of gallated catechins significantly increased from catechins formulated with vitamin C and xylitol in a dose‐dependent manner compared to the catechin‐only formulation. Results provide a potential strategy to enhance the delivery and bioavailability of catechins in humans by modulating green tea formulation with vitamin C and xylitol.     

Comparison of catechins and volatile compounds among different types of tea using high performance liquid chromatograph and gas chromatograph mass spectrometer

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.     

Antiviral activity of green tea catechins against feline calicivirus as a surrogate for norovirus

In this study, several medicinal plant extracts including spices, herb teas, and medical herbs were screened for antiviral activity against feline calicivirus (FCV), a surrogate of norovirus. Among them, a methanolic extract of green tea, Camellia sinensis, only exhibited a significant antiviral activity against FCV. The methanolic extract was further fractionated with several solvents such as methanol (MeOH), n-hexane, chloroform (CHCl₃), ethyl acetate (EtOAc), n-butanol (n-BuOH), and water. EtOAc-soluble fraction exhibited the highest antiviral activity against FCV. Moreover, the analysis of the most active fraction using a HPLC led to the identification of 4 known catechins: (-)-epigallocatechin (EGC), (-)-epicatechin (EC), (-)-epigallocatechin gallate (EGCG), and (-)-epicatechin gallate (ECG). Among the catechins tested in this study, EGCG exhibited the most effective antiviral activity (EC₅₀, 12 mg/mL) with relatively low cytotoxicity (CC₅₀, 320 mg/ mL), resulting relatively high selectivity index value 26.67. To our knowledge, this is the first experimental verification showing antiviral activity of catechins from green tea against FCV.     

不同季节信阳毛尖茶主要生化成分及其矿质元素差异性分析

目的 基于不同季节信阳毛尖茶的生化成分和矿质元素,探究多元统计分析方法对不同季节信阳毛尖茶的有效区分。方法 采用高效液相色谱法等化学方法对64种信阳毛尖茶主要生化成分及其矿质元素进行检测分析,结合正交矫正偏最小二乘法判别分析获取不同季节茶样的组间差异。结果 研究结果表明游离氨基酸、黄酮类物质、水溶性碳水化合物、非酯型儿茶素、表儿茶素(epicatechin,EC)、表没食子儿茶素(epigallocatechin,EGC)、没食子酸(gallic acid,GA)及矿质元素均存在季节性显著差异。判别分析可将信阳毛尖春茶和夏秋茶明显区分,并鉴定出黄酮类物质、游离氨基酸、GA、儿茶素(catechin,C)、EC、EGC、Mg和Zn 8种判别不同季节信阳毛尖茶的重要差异化合物。热图分析结果进一步证实,茶多酚、游离氨基酸、C、表儿茶素没食子酸酯(epicatechin gallate,ECG)和GA等物质主要在春茶中积累,黄酮类物质、EGC、表没食子儿茶素没食子酸酯(epigallocatechin gallate,EGCG)、Mg、Fe、Zn和Se等物质主要在夏秋茶上积累。结论 本研究鉴别了不同季节信阳毛尖茶的特征性差异化合物,为信阳毛尖茶的季节识别提供理论基础。     

The development of a suitable manufacturing process for ‘Benifuuki’ green tea beverage with anti‐allergic effects

Epigallocatechin‐3‐O‐(3‐O‐methyl) gallate (EGCG3″Me) has been reported to inhibit type I allergy better than epigallocatechin gallate (EGCG), a major catechin in tea leaves (Camellia sinensis L). We examined the effects of extraction and sterilization on the catechin content and histamine release from mast cells, as a representative reaction of early phase allergy, in the manufacture of ‘Benifuuki’ green tea beverage. Among various varieties of tea, the cultivar ‘Benifuuki’ contains approximately 2% of EGCG3″Me. Ester‐type catechins and their epimers increased with the increased extraction temperature of the tea. A tea infusion, extracted at 90 °C, strongly inhibited histamine release from mast cells. Furthermore, sterilization affected the catechin content in the manufactured green tea beverage. Sterilization at high temperature promoted the isomerization of catechins and the sterilized green tea beverage had a strong inhibitory effect. When EGCG3″Me, EGCG, epicatechin‐3‐O‐gallate (ECG) and their epimers, GCG3″Me (gallocatechin‐3‐O‐(3‐O‐methyl) gallate), GCG (gallocatechin‐3‐O‐gallate) and CG (catechin‐3‐O‐gallate) were compared, the anti‐allergic effect of GCG3″Me was strongest, and the order of activity was GCG3″Me > EGCG3″Me > GCG > EGCG. We consequently suggest that it was necessary to extract components from tea at the highest temperature possible, and to pasteurize under retort conditions (118.1 °C, 20 min), to manufacture functional green tea beverage with an anti‐allergic action. Copyright © 2005 Society of Chemical Industry     

Epimerisation of tea polyphenols in tea drinks

The present study was carried out to quantify green tea epicatechin (GTE) derivatives and to investigate the origin of epicatechin epimers present in 18 selected canned or bottled tea drinks. The major GTEs present in tea are (?)‐epigallocatechin gallate (EGCG), (?)‐epigallocatechin (EGC), (?)‐epicatechin gallate (ECG) and (?)‐epicatechin (EC). HPLC analysis showed that the content of total GTEs was lower (16.4–268.3 mg l^?1) in the canned and bottled tea drinks than in tea traditionally prepared as a beverage in a cup or teapot (3–5 g l^?1). The major finding was that they contained higher levels of epicatechin epimers, namely (?)‐gallocatechin gallate (GCG), (?)‐gallocatechin (GC), catechin gallate (CG) and (?)‐catechin (C), than of GTEs, ranging from 7.6 to 331.8 mg l^?1. To investigate the origin of these epimers, GTEs were extracted from longjing green tea and autoclaved at various temperatures for 10–60 min. It was found that at least 50% of GTEs were epimerised to their corresponding epimers when autoclaved at 120 °C for 20 min. It is concluded that epicatechin epimers in tea drinks are not originally present in green tea leaf but are instead derived from thermal conversion of GTEs. Copyright © 2003 Society of Chemical Industry     

Comparison of catechins and purine alkaloids in albino and normal green tea cultivars (Camellia sinensis L.) by HPLC

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.     

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.     

高效液相色谱法对“黄金菊”茶中儿茶素和氨基酸组分含量的测定

为进一步研究江西特色茶树资源的生化成分,以“黄金菊”、安吉白茶、福鼎大白茶等茶树为试验材料,用高效液相色谱(high performance liquid chromatography,HPLC)法,对不同茶叶中儿茶素组分和氨基酸组分进行检测和对比分析。结果显示,“黄金菊”茶中儿茶素组分和氨基酸组分比较丰富,没食子酸酯儿茶素(gallate catechin,GC)、表没食子儿茶素(epigallocatechin,EGC)、儿茶素(catechin,C)、表儿茶素(epicatechin,EC)、表没食子儿茶素没食子酸酯(epigallocatechin gallate,EGCG)、没食子儿茶素没食子酸酯(gallocatechin gallate,GCG)、表儿茶素没食子酸酯(epicatechin gallate,ECG)、儿茶素没食子酸酯(catechin gallate,CG)含量分别为0.05%、1.21%、0.53%、0.99%、7.91%、0.23%、2.63%、0.01%;共检测出17种氨基酸组分,分别比安吉白茶、福鼎大白茶多检出1、3种氨基酸,检测出的成分含量与安吉白茶比较接近。试验结果说明,"黄金菊"茶树中儿茶素组分、氨基酸组分丰富,同时特征成分明显。     

儿茶素的分析比较研究

本文首先研究了采用不同标样儿茶素(C)，表儿茶素(EC)和没食子儿茶素没食子酸酯(EGCG)对样品茶多酚中总儿茶素含量分光光度法测定带来的影响，其测定结果儿茶素纯度分别为51．98％，49．59％和82．39％，相对标准偏差分别为0．65％，1.79％和2．28％，回收率分别为94．19％，93．46％和102．4％。结果表明使用异构体C和EC作标样测定结果相近，而采用分子量较大的EGCG作标样时结果偏高。最后本文采用高效液相色谱法(HPLC)对样品茶多酚进行了定性定量研究，结果表明C、EC、EGC(表没食子儿茶素)、ECG(表儿茶素没食子酸酯)和EGCG等五种儿茶素单体的含量分别为5．05％、10．38％，、25．96％、1．98％，和10．18％，总儿茶素含量为53．5％，其测定结果与分光光度法(以C为标样）所测结果相一致。