Main Catechin Research Articles

Geography and the therapeutic effect of matcha tea in drinks

Camellia sinensis belonging to family Theaceae, commonly called as tea is the most widely used refreshing beverage accepted globally. It has two variety such as Green tea and black depending upon its method of cultivation. Green teas are non-fermented minimally oxidized variety of tea. Green tea has also attracted the research limelight because of its variety of Phenols with versatile pharmacology and health effects. There are wide range of green tea some are Biluochun, Gunpowder, Genmaicha, Matcha, Sencha. Matcha which commonly originates in Japan and is a type of powdered green tea, cultivated and produced in a traditional way. Shading of the plants during the growth period enhances the processes of accumulation and synthesis of biologically active compounds, including caffeine, theanine, chlorophyll and various types of catechins. Retention of chlorophyll results in soothing green colour of tea and theanine for it non bitter taste. Green tea contains four main catechins, i.e., (−)-epicatechin-3-gallate (ECG), (−)-epicatechin (EC), (−)-epigallocatechin-3-gallate (EGCG) and (−)-epigallocatechin (EGC), of which (−)-epigallocatechin-3-gallate (EGCG) is the most active and is present in abundance and matcha is their best condensed source. Matcha tea is considered as highest quality tea Due to its unique chemical composition and texture, which also sets it apart from other tea beverages. Its high content of antioxidant and anti-inflammatory substances attributes the various health-promoting properties. Due to its potential for preventing many diseases and illness, regular consumption of matcha may have a positive effect on both physical and mental health. The aim of this review was to compile the native origin and health benefits of matcha tea along with its side effects.

Comparison of migration disturbance potency of epigallocatechin gallate (EGCG) synthetic analogs and EGCG PEGylated PLGA nanoparticles in rat neurospheres

Epigallocatechin gallate (EGCG), the main catechin of green tea, is described to have potential health benefits in several fields like oncology, neurology or cardiology. Currently, it is also under pre-clinical investigation as a potential therapeutic or preventive treatment during pregnancy against developmental adverse effects induced by toxic substances. However, the safety of EGCG during pregnancy is unclear due to its proven adverse effects on neural progenitor cells' (NPCs) migration. As lately several strategies have arisen to generate new therapeutic agents derived from EGCG, we have used the rat ‘Neurosphere Assay’ to characterize and compare the effects of EGCG structurally related compounds and EGCG PEGylated PLGA nanoparticles on a neurodevelopmental key event: NPCs migration. Compounds structurally-related to EGCG induce the same pattern of NPCs migration alterations (decreased migration distance, decreased formation of migration corona, chaotic orientation of cellular processes and decreased migration of neurons at higher concentrations). The potency of the compounds does not depend on the number of galloyl groups, and small structure variations can imply large potency differences. Due to their lower toxicity observed in vitro in NPCs, 4,4′-bis[(3,4,5-trihydroxybenzoyl)oxy]-1,1′-biphenyl and EGCG PEGylated PLGA nanoparticles are suggested as potential future therapeutic or preventive alternatives to EGCG during prenatal period.

The Effect of Ultrasound, Oxygen and Sunlight on the Stability of (-)-Epigallocatechin Gallate.

(−)-Epigallocatechin gallate (EGCG), is the main catechin found in green tea, and has several beneficial effects. This study investigated the stability of EGCG aqueous solution under different stored and ultrasonic conditions to determine whether it can be used with an ultrasonic dental scaler to treat periodontal infection. Four concentrations (0.05, 0.1, 0.15, 2 mg/mL) of EGCG aqueous solution were prepared and stored under four different conditions (A: Exposed to neither sunlight nor air, B: Exposed to sunlight, but not air, C: Not exposed to sunlight, but air, D: Exposed to sunlight and air) for two days. The degradation rate of EGCG was measured by high performance liquid chromatography (HPLC). On the other hand, an ultrasonic dental scaler was used to atomize the EGCG solution under four different conditions (a: Exposed to neither air nor sunlight, b: Not exposed to air, but sunlight, c: Not exposed to sunlight, but air, d: Exposed to air and sunlight), the degradation of EGCG was measured by HPLC. We found that the stability of EGCG was concentration-dependent in water at room temperature. Both sunlight and oxygen influenced the stability of EGCG, and oxygen had a more pronounced effect on stability of EGCG than sunlight. The most important conclusion was that the ultrasound may accelerate the degradation of EGCG due to the presence of oxygen and sunlight, but not because of the ultrasonic vibration. Thus, EGCG aqueous solution has the potential to be used through an ultrasonic dental scaler to treat periodontal infection in the future.

Difference in formation mechanism of inclusion complex between configuration isomers of gallate-type catechin and β-cyclodextrin

The formation mechanism of inclusion complex between (-)-epigallocatechin gallate (EGCg), which is the main catechin in tea leaves, or (-)-gallocatechin gallate (GCg), which is an isomer of EGCg, and β-cyclodextrin (βCD) was studied by isothermal titration microcalorimetry (ITC), NMR and molecular modeling calculation (MMC). ITC measurements revealed that EGCg or GCg interacted with βCD at 1:1 molar ratio driven by enthalpy. Comparing the values of binding constant (7.2 × 103 1/M for EGCg with βCD and 3.9 × 104 1/M for GCg with βCD), it was suggested that GCg interacted with βCD more strongly rather than EGCg. In their ROESY NMR spectra, the cross-peaks were observed between the protons of A, B and B′ ring of EGCg and the protons in the cavity of βCD, and between the protons of B and B′ ring of GCg and the protons in the cavity of βCD. MMC in water showed that EGCg had one kind and GCg had two kinds of most stable conformation (GCg(E) and GCg(A)) in energy. In the stable conformation of EGCg, B ring was coordinated equatorially to C ring, and B′ ring was axially coordinated to C ring. On the other hand, in GCg (E), the coordination of B ring and B′ ring to C ring was both equatorial, and in GCg (A), the coordination of B ring and B′ ring was both axial. MMC also revealed B or B′ ring of GCg(A) was easy to be included in the cavity of βCD more deeply than each ring of EGCg or GCg(E) since the steric hindrance of B ring or B′ ring was small. Therefore, it was found that the difference of B ring’s configuration of gallate-type catechin greatly affected the formation of inclusion complex with βCD.

Epigallocatechin-3-gallate and 6-OH-11-O-Hydroxyphenanthrene Limit BE(2)-C Neuroblastoma Cell Growth and Neurosphere Formation In Vitro.

We conducted an in vitro study combining a rexinoid, 6-OH-11-O-hydroxyphenanthrene (IIF), and epigallocatechin-3-gallate (EGCG), which is the main catechin of green tea, on BE(2)-C, a neuroblastoma cell line representative of the high-risk group of patients. Neuroblastoma is the most common malignancy of childhood: high-risk patients, having N-MYC over-expression, undergo aggressive therapy and show high mortality or an increased risk of secondary malignancies. Retinoids are used in neuroblastoma therapy with incomplete success: the association of a second molecule might improve the efficacy. BE(2)-C cells were treated by EGCG and IIF, individually or in combination: cell viability, as evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, was reduced, EGCG+IIF being the most effective treatment. Apoptosis occurred and the EGCG+IIF treatment decreased N-MYC protein expression and molecular markers of invasion (MMP-2, MMP-9 and COX-2). Zymography demonstrated nearly 50% inhibition of MMP activity. When BE(2)-C cells were grown in non-adherent conditions to enrich the tumor-initiating cell population, BE(2)-C-spheres were obtained. After 48 h and 72 h treatment, EGCG+IIF limited BE(2)-C-sphere formation and elicited cell death with a reduction of N-MYC expression. We concluded that the association of EGCG to IIF might be applied without toxic effects to overcome the incomplete success of retinoid treatments in neuroblastoma patients.

Green Tea Catechins: Their Use in Treating and Preventing Infectious Diseases.

Green tea is one of the most popular drinks consumed worldwide. Produced mainly in Asian countries from the leaves of the Camellia sinensis plant, the potential health benefits have been widely studied. Recently, researchers have studied the ability of green tea to eradicate infectious agents and the ability to actually prevent infections. The important components in green tea that show antimicrobial properties are the catechins. The four main catechins that occur in green tea are (-)-epicatechin (EC), (-)-epicatechin-3-gallate (ECG), (-)-epigallocatechin (EGC), and (-)-epigallocatechin-3-gallate (EGCG). Of these catechins, EGCG and EGC are found in the highest amounts in green tea and have been the subject of most of the studies. These catechins have been shown to demonstrate a variety of antimicrobial properties, both to organisms affected and in mechanisms used. Consumption of green tea has been shown to distribute these compounds and/or their metabolites throughout the body, which allows for not only the possibility of treatment of infections but also the prevention of infections.

Epigallocatechin-3-Gallate suppresses neutrophil accumulation and the IL-1 beta pathway in a transgenic zebrafish model of inflammation

Abstract Background The zebrafish represents the simplest and most convenient vertebrate model for undertaking large screens because of its small size, rapid reproduction time and transparency of the body. Here, we adopt a well-established model of inflammation in zebrafish to assess the impact of Epigallocatechin-3-Gallate (EGCG), the main catechin in green tea. Method Tg (MPX:GFP) or Tg (MPX:mCHERRY) transgenic zebrafish were used, bearing GFP- or mCherry-tagged neutrophils, respectively. 4dpf embryos were anesthetized, and inflammation was induced by sterile tailfin-resection. The inflamed groups were separated into those that were non-treated or exposed to EGCG from 0 – 600 uM for 6 hours. 10 fish per group were then mounted alive in methyl cellulose for wide-field fluorescence imaging and analysis was done using ImageJ. Animation of neutrophil migration or accumulation was recorded using an inverted fluorescence confocal microscope till 6-hours after resection. To examine the mechanistic basis of EGCG’s effect, 37 zebrafish inflammatory genes were studied using qPCR. Results The static accumulation of neutrophils at the resection site was highly elevated after wounding (n=32, p<0.0001), and this accumulation was reduced significantly by 31% and 43%, respectively, after exposure to EGCG 300 uM (p<0.05) and 600 uM (p<0.01). Dynamic neutrophil tracking studies are in progress. qPCR studies revealed 6 signature genes in the IL-1 beta pathway to be significantly down-regulated at least 2-fold after EGCG treatment. Conclusion EGCG suppresses inflammation in zebrafish through similar biochemical pathways as in other species. This novel animal model allows facile screening of inflammatory modulators in real-time.

P-218 - Antioxidant properties of ferrous catechin complexes

Interaction of metal, especially iron ions with catechins is considered as an important feature of these compounds and is believed to contribute to their both antioxidant and prooxidant properties. The aim of this study was to examine how Fe2+binding to form a 1:1 complex affects the antioxidant properties of catechins (flavan-3-ols). The following catechins were used in the study: (-)-epigallocatechin gallate, (−)-epicatechin, (−)-epigallocatechin, (−)-epicatechin gallate and (+)-catechin. They represent the main catechins present in the green tea. Iron complexes of various stoichiometry can be formed, but under the conditions of catechin excess, formation of 1:1 complexes can be expected ABTS* scavenging, protection against fluorescence bleaching induced by AAPH and hypochlorite, and protection against hypochlorite-induced hemolysis demonstrated that catechin-Fe2+complexes retain antioxidant properties, although, in most cases, they are lower with respect to uncomplexed catechins. No superoxide dismutase-like or catalase-like activity of the complexes was revealed.

Evaluation of thrombin inhibitory activity of catechins by online capillary electrophoresis-based immobilized enzyme microreactor and molecular docking

An online capillary electrophoresis (CE)-based thrombin (THR) immobilized enzyme microreactor (IMER) method was established to screen THR inhibitors in this study. S-2366 was used as chromogenic substrate for determination of THR activity and other kinetic constants. After continuously run for 50 times, the prepared IMER could still remain 89% of the initial immobilized enzyme activity. The Michaelis-Menten constant (Km) of immobilized THR was measured as 0.514 mmol/L and the half-maximal inhibitory concentration (IC50) and inhibition constant (Ki) of argatroban on THR were determined as 78.07 and 26.53 nmol/L, respectively, which indicated that CE-based THR IMER was successfully established and could be applied to screen THR inhibitors. Then the prepared IMER was used to investigate the inhibitory potency on THR of four main catechins in green tea including epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG). The results showed that ECG and EGCG had good THR inhibition activity and their inhibition rates at concentration of 200 μmol/L were 53.2 ± 3.8% and 55.8 ± 2.6%, respectively, which was in consistent with the results of microplate reader assay. Additionally, molecular docking results showed that the benzopyran groups of ECG and EGCG were inserted into the THR active pocket and interacted with residues LYS60F, TRP60D, TRY60A, IEU99, GLY216, HIS57 and SER195, but EC and EGC did not. Therefore, the developed CE-based THR IMER is reliable method for measuring THR inhibitory activity of natural inhibitors.

White tea intake interferes with the expression of angiogenic factors in the corpora lutea of superovulated rats

SummaryWhite tea derived from the Camellia sinensis (L.) plant has anticancer effects. Its main catechin decreases the gene expression of Vegf in tumours. However, VEGF is also the angiogenic factor of the reproductive organs. In this study, Wistar rats were divided into the following groups (n = 30): the control group (CT), which received water, and the white tea intake group (WT), for 3 months. At the end of every month, the corpora lutea (CL) of ten rats were removed to evaluate the gene expression of Vegf and its receptors (Flt‐1 and Kdr). White tea increased the relative mRNA abundance of Vegf (CT = 0.95 ± 0.06 and WT = 2.13 ± 0.19), Kdr (CT = 0.88 ± 0.06 and WT = 1.94 ± 0.32) and Flt‐1 (CT = 0.94 ± 0.06 and WT = 2.11 ± 0.22) in CL (P < 0.05). White tea increased angiogenic‐related genes in rat CL but did not alter the number of rat CL.

The Anti-Obesity Potential of Green Tea: The Effect on Leptin and Adiponectin

Green tea has been consumed for thousands of years, and has been known to have many medicinal properties such as, anti-cancerous, anti-atherogenic, anti-oxidative, anti-inflammatory and anti-bacterial. With the increasing emergence of cardiovascular disease (CVD), and its major risk factor, obesity, there has been increasing interest in green tea as a potential anti-obesity therapy. Evidence has demonstrated that green tea decreases body weight. However it remains unclear through which pathway and mechanism green tea exerts its anti-obesity properties. The metabolic adipose tissue hormones, adipocytokines, leptin and adiponectin have been studied extensively as a potential target for green tea and its main catechin, epigallacatechin gallate (EGCG). It has been demonstrated that green tea consumption decreases leptin levels which may directly decrease body weight through increasing energy expenditure and fat oxidation. Furthermore, ingestion of green tea or its catechins has been associated with increased adiponectin levels which may indirectly reduce body weight through insulin sensitivity.

An Appraisal of Drug-Drug Interactions with Green Tea (Camellia sinensis)

This review summarizes published in vitro, animal, and clinical studies investigating the effects of green tea (Camellia sinensis) extract and associated catechins on drug-metabolizing enzymes and drug transporters. In vitro studies suggest that green tea extract and its main catechin, (-)-epigallocatechin-3-gallate, to varying degrees, inhibit the activity of CYP1A1, CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2D6, and CYP3A4. UGT1A1 and UGT1A4 isoforms were also inhibited by (-)-epigallocatechin-3-gallate. Animal studies suggest green tea extract and/or (-)-epigallocatechin-3-gallate significantly increase the bioavailability of diltazem, verapamil, tamoxifen simvastatin, 5-fluorouracil, and nicardipine. Conversely, green tea extract and/or (-)-epigallocatechin-3-gallate reduce the bioavailability of quetiapine, sunitinib, clozapine, and nadolol. Of the few clinical studies available for review, it appears neither green tea extract nor (-)-epigallocatechin-3-gallate inhibit any major cytochrome P450 enzyme. Regarding drug transporters, in vitro studies indicate P-glycoprotein, organic anion transporting polypeptide 1A1, organic anion transporting polypeptide 1B1, organic anion transporting polypeptide 1B3, organic anion transporting polypeptide 2B1, organic cation transporter 1, organic cation transporter 2, multidrug and toxin extrusion 1, and multidrug and toxin extrusion 2-K are potentially inhibited by green tea extract. A clinical study indicates the organic anion transporting polypeptide 1A1 transporter is inhibited by (-)-epigallocatechin-3-gallate while P-glycoprotein is unaffected. In conclusion, the ingestion of green tea extract or its associated catechins is not expected to result in clinically significant influences on major cytochrome P450 or uridine 5'-diphospho-glucuronosyltransferase enzyme substrates or drugs serving as substrates of P-glycoprotein. However, some caution is advised in the consumption of significant amounts of green tea beverages or green tea extract in patients prescribed known substrates of organic anion transporting polypeptide, particularly those with a narrow therapeutic index.

An Update on the Health Benefits of Green Tea

Green tea, which is produced from the leaves of the Camellia sinensis plant, is one of the most popular beverages worldwide. Over the past 30 years or more, scientists have studied this plant in respect to potential health benefits. Research has shown that the main components of green tea that are associated with health benefits are the catechins. The four main catechins found in green tea are: (−)-epicatechin (EC), (−)-epicatechin-3-gallate (ECG), (−)-epigallocatechin (EGC), and (−)-epigallocatechin-3-gallate (EGCG). Of these four, EGCG is present in the largest quantity, and so has been used in much of the research. Among the health benefits of green tea are: anticarcinogenic, anti-inflammatory, antimicrobial, and antioxidant properties, and benefits in cardiovascular disease and oral health. Research has been carried out using various animal models and cells lines, and is now more and more being carried out in humans. This type of research will help us to better understand the direct benefits of green tea. This review will focus primarily on research conducted using human subjects to investigate the health benefits of green tea.

ErbB Proteins as Molecular Target of Dietary Phytochemicals in Malignant Diseases.

ErbB proteins overexpression, in both normal and mutated forms, is associated with invasive forms of cancer prone to metastasis and with stronger antiapoptotic mechanisms and therefore more challenging to treat. Downstream effectors of ErbB receptors mediating these phenotypic traits include MAPK, STAT, and PI3K/AKT/mTOR pathways. Various phytochemical compounds were studied for their large number of biological effects including anticancer activity. Among these compounds, epigallocatechin-3-gallate (EGCG), the main catechin from green tea leaves, and curcumin, component of the curry powder, constituted the object of numerous studies. Both compounds were shown to act directly either on ErbB expression, or on their downstream signaling molecules. In this paper we aim to review the involvement of ErbB proteins in cancer as well as the biologic activity of EGCG and curcumin in ErbB expressing and overexpressing malignancies. The problems arising in the administration of the two compounds due to their reduced bioavailability when orally administered, as well as the progress made in this field, from using novel formulations to improved dosing regimens or improved synthetic analogs, are also discussed.

Simultaneous Determination of Catechins and Caffeine in Green Tea-Based Beverages and Foods for Specified Health Uses

Catechins in green tea have various useful features including antioxidant activity and preventive effects on metabolic syndrome. Various beverages that are enriched with tea catechins are marketed as Foods for Specified Health Uses (FOSHU) in Japan. However, recent reports have indicated that excessive consumption of green tea extracts as a dietary supplement are associated with adverse health effects such as liver disorders. Various catechins and caffeine are constituents of FOSHU tea-based beverages. The amount of catechins in FOSHU products is displayed on labels as total catechin content, but the content of individual catechins are not provided. Although health hazards of FOSHU products have rarely been reported, precise information about the content and types of catechins in FOSHU products is needed to ensure safety. We used high-performance liquid chromatography with a photodiode array (HPLC/PDA) to simultaneously identify and quantify catechins and caffeine in green tea-based popular beverages and FOSHU beverages. This technique allowed simultaneous quantitation of five types of catechins and caffeine in green tea without complicated sample preparation. Epigallocatechin gallate (EGCG) and epigallocatechin EGC were the main catechins in various FOSHU beverages and the concentrations of almost all catechins were higher in FOSHU, than in popular green tea-based beverages. The concentrations of EGCG in green tea-based popular beverages and in FOSHU beverages were 5.4 - 7.3 and 10.2 - 41.9 mg/100mL, respectively, with the highest concentration being in a product named Healthya (approximately 147 mg/bottle). The simultaneous determination of compounds such as catechins and caffeine in FOSHU beverages can help to estimate beneficial and adverse effects to prevent deleterious effects on health and the excessive consumption of FOSHU beverages containing high concentrations of tea catechins should be avoided.

Anti-stress effects of drinking green tea with lowered caffeine and enriched theanine, epigallocatechin and arginine on psychosocial stress induced adrenal hypertrophy in mice

BackgroundTheanine, an amino acid in tea, has significant anti-stress effects on animals and humans. However, the anti-stress effects of drinking green tea have not yet been elucidated. Hypothesis/purposeThe present study aimed to explore anti-stress effects of green tea and roles of tea components in a mouse model of psychosocial stress. Study designWe examined anti-stress effects of three types of green teas, theanine-rich “Gyokuro”, standard “Sencha”, and Sencha with lowered caffeine (low-caffeine green tea). Furthermore, the roles of tea components such as caffeine, catechins, and other amino acids in anti-stress effects were examined. MethodsTo prepare low-caffeine green tea, plucked new tea leaves were treated with a hot-water spray. Mice were psychosocially stressed from a conflict among male mice under confrontational housing. Mice consumed each tea that was eluted with room temperature water ad libitum. As a marker for the stress response, adrenal hypertrophy was compared with mice that ingested water. ResultsCaffeine was significantly lowered by spraying hot-water on tea leaves. While epigallocatechin gallate (EGCG) is the main catechin in tea leaves, epigallocatechin (EGC) was mainly infused into water at room temperature. Adrenal hypertrophy was significantly suppressed in mice that ingested theanine-rich and low-caffeine green tea that were eluted with water at room temperature. Caffeine and EGCG suppressed the anti-stress effects of theanine while EGC and arginine (Arg) retained these effects. ConclusionThese results suggest that drinking green tea exhibits anti-stress effects, where theanine, EGC and Arg cooperatively abolish the counter-effect of caffeine and EGCG on psychosocial stress induced adrenal hypertrophy in mice.

Inhibition of green tea and the catechins against 1-deoxy-d-xylulose 5-phosphate reductoisomerase, the key enzyme of the MEP terpenoid biosynthetic pathway

1-Deoxy-d-xylulose 5-phosphate reductoisomerase (DXR) is the first committed enzyme in the MEP terpenoid biosynthetic pathway and also a validated antimicrobial target. Green tea which is rich in polyphenolic components such as the catechins, possesses a plenty of pharmacological activities, in particular an antibacterial effect. To uncover the antibacterial mechanism of green tea and to seek new DXR inhibitors from natural sources, the DXR inhibitory activity of green tea and its main antimicrobial catechins were investigated in this study. The results show that the raw extract of green tea and its ethyl acetate fraction are able to suppress DXR activity explicitly. Further determination of the DXR inhibitory capacity of eight catechin compounds demonstrates that the most active compound is gallocatechin gallate that is able to inhibit around 50% activity of DXR at 25μM. Based on these data, the primary structure-activity relationship of the catechins against DXR is discussed. This study would be very helpful to elucidate the antimicrobial mechanism of green tea and the catechins and also would be very useful to direct the rational utilization of them as food additives.

Comparison of Some Extraction Methods for Isolation of Catechins and Caffeine from Turkish Green Tea

Effective extraction of anticancer and antioxidant principles from Turkish green tea were main purpose of this work. The pre-optimized experimental condition for liquid extraction was employed for comparative appraisal. Not only extraction methods also nature of the green tea samples (fresh, dried or frozen) and quantitative yields related to collection periods were investigated. After extraction of the green tea with various techniques the extract was partitioned with chloroform to remove caffeine, after that the extract was partitioned with ethyl acetate to obtain catechin mixture. Quantification of individual catechins was carried out by HPLC and analysis results proved that epigallocatechin gallate (EGCG) was main catechin specie present in all extracts. The results indicate that hot water extraction (at 80 0C) provides higher catechin yield when compared to other methods. The highest extract yields were obtained with dried leaves collected in second collection period. The crude catechin mixture contains high amount of EGCG and might be used as raw material for production of plant remedies at industrial scale.

Stepwise Identification of Six Tea (Camellia sinensis (L.)) Categories Based on Catechins, Caffeine, and Theanine Contents Combined with Fisher Discriminant Analysis

Six tea types were stepwise discriminated based on their catechins, caffeine, and theanine contents of total 436 tea samples collected worldwide, combined with Fisher classification pattern recognition. Those tea samples of six types (green, white, yellow, oolong, black, and dark teas) of commonly consumed teas with different processing methods were analyzed in this work. Five main catechins ((−)-epigallocatechin gallate (EGCG), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECG), (−)-epicatechin (EC), and (+)-catechin (C)), caffeine, and theanine contents were accurately measured by high-performance liquid chromatography (HPLC). As a novel approach, stepwise identification combined with Fisher discriminant analysis was applied to develop an identification model. Several parameters, including model component factors, were optimized by cross-validation. The optimal Fisher model was achieved with caffeine, total catechins, theanine, theanine × theanine, EGCG/total catechins, and theanine × caffeine as component factors. The discrimination rates of black, dark, white, oolong, yellow, and green teas were 95.90, 100.00, 97.40, 95.70, 91.80, and 88.30 %, respectively. Compared with other pattern recognition approaches, the Fisher algorithm exhibited excellent performance in the final identification. The overall results show that this method is suitable to stepwise identify six tea categories, according to the measurements of main chemicals with catechins, caffeine, and theanine by HPLC and followed by the Fisher pattern recognition.

Altering the phenolics profile of a green tea leaves extract using exogenous oxidases

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.