Reaction kinetics of degradation and epimerization of epigallocatechin gallate (EGCG) in aqueous system over a wide temperature range

(-)-Epigallocatechin gallate (EGCG) is the most abundant catechin in green tea, which has been linked with many health benefits. To ensure the conceivable health benefits from thermally processed products, a kinetic study on the stability of (-)-EGCG in aqueous system was carried out using a HPLC-UV system and Matlab programming. Simultaneous degradation and epimerization of (-)-EGCG were characterized during isothermal reactions at low temperatures (25-100 degrees C) combined with previously conducted experimental results at high temperature (100-165 degrees C); the degradation and epimerization complied with first-order reaction and their rate constants followed Arrhenius equation. Mathematical models for the stability of (-)-EGCG were established and validated by the reactions at 70 degrees C and with varied concentrations from different catechin sources. Two specific temperature points in the reaction kinetics were identified, at 44 and 98 degrees C, respectively. Below 44 degrees C, the degradation was more profound. Above 44 degrees C, the epimerization from (-)-gallocatechin gallate (GCG) to (-)-EGCG was faster than degradation. When temperature increased to 98 degrees C and above, the epimerization from (-)-GCG to (-)-EGCG became prominent. Our results also indicated that the turning point of 82 degrees C reported in the literature for the reaction kinetics of catechins would need to be re-examined.     

Degradation of green tea catechins in tea drinks

Green tea cateachins (GTC). namely (-) epicatechin (EC), (-) epicatechin gallate (ECG), (-) epigallocatechin (EGC), and (-) epigallocatechin gallate (EGCG), have been studied extensively for their wide-ranging biological activities. The goal of the present study was to examine the stability of GTC as a mixture under various processing conditions. The stability study demonstrated that GTC was stable in water at room temperature. When it was brewed at 98 degrees C for 7 h, longjing GTC degraded by 20%. When longjing GTC and pure EGCG were autoclaved at 120 degrees C for 20 min, the epimerization of EGCG to (-) gallocatechin gallate (GCG) was observed. The relatively high amount of GCG found in some tea drinks was most likely the epimerization product of EGCG during autoclaving. If other ingredients were absent, the GTC in aqueous solutions was pH-sensitive: the lower the pH, the more stable the GTC during storage. When it was added into commercially available soft drinks or sucrose solutions containing citric acid and ascorbic acid, longjing GTC exhibited varying stability irrespective of low pH value. This suggested that other ingredients used in production of tea drinks might interact with GTC and affect its stability. When canned and bottled tea drinks are produced, stored, and transported, the degradation of GTC must be taken into consideration.     

Inhibitory Effects of the C-2 Epimeric Isomers of Tea Catechins on Mouse Type IV Allergy

The inhibitory effects of C-2 epimeric isomers of (-)-epigallocatechin-3-O-gallate (EGCG) and two O-methylated EGCG derivatives, (-)-epigallocatechin-3-O-(3-O-methyl)gallate (EGCG3'Me) and (-)-epigallocatechin-3-O-(4-O-methyl)gallate (EGCG4'Me), against oxazolone-induced type IV allergy in male mice were investigated. These compounds exhibited strong antiallergic effects by percutaneous administration at a dose of 0.13 mg/ear. The inhibition rates of (-)-gallocatechin-3-O-gallate (GCG), (-)-gallocatechin-3-O-(3-O-methyl)gallate (GCG3'Me), and (-)-gallocatechin-3-O-(4-O-methyl)gallate (GCG4'Me) on mouse type IV allergy were 52.1, 53.3, and 54.8%, respectively. However, the antiallergic effects were weaker than those of their corresponding original tea catechins (2R,3R type). The inhibition rates of those were 88.0, 73.2, and 77.6%, respectively. For all of the catechins tested, oral administration at a dose of 50 mg/kg body weight significantly suppressed the allergic symptoms. The inhibitory rates varied from 24.0 to 60.6%. No significant differences were observed between the effects of the epimers (2S,3R type) and their corresponding original catechins (2R,3R type). The antiallergic effects of tea catechins and their C-2 epimers observed in this study were dose-dependent. These results suggest that C-2 epimers of tea catechins, which are produced during heat processing at high temperatures, could be disadvantageous for the antiallergic effects on type IV allergy.     

Polyphenol content of plasma and litter after the oral administration of green tea and tea polyphenols in chickens

Metabolic profiles of broiler chickens were examined after the ingestion of green tea, tea polyphenols, and (-)-epigallocatechin-3-gallate (EGCG). Solid-phase extraction of serum and litters yielded free catechins and their metabolites, which were then identified and quantified by liquid chromatography-tandem mass spectrometry. In plasma samples, (-)-gallocatechin, (+)-catechin, and EGCG were detected in the green tea group; pyrogallol acid, (epi)catechin-O-sulfate, 4'-O-methyl-(epi)gallocatechin-O-glucuronide, and (epi)catechin-3'-O-glucuronide were detected in the tea polyphenols group; and EGCG, (-)-gallocatechin gallate (GCG), and 4'-O-methyl-(epi)gallocatechin-O-glucuronides were detected in the EGCG group. In litters, gallic acid, EGCG, GCG, and ECG were detected in the green tea and tea polyphenols groups; EGCG and ECG were detected in the EGCG group. The conjugated metabolites, 4'-O-methyl-(epi)gallocatechin-O-glucuronide, (epi)catechin-3'-glucuronide, and 4'-O-methyl-(epi)catechin-O-sulfate, were identified in the green tea group; 4'-O-methyl-(epi)catechin-O-sulfate and 4'-O-methyl-(epi)gallocatechin-O-sulfate were identified in the tea polyphenols group; only 4'-O-methyl-(epi)gallocatechin-O-sulfate was detected in the EGCG group. The excretion of tea catechins was 95.8, 87.7, and 97.7% for the green tea, tea polyphenols, and EGCG groups, respectively.     

Stability of tea catechins in the breadmaking process

A green tea extract (GTE) was incorporated into bread as a source of tea catechins. The stability of tea catechins in the breadmaking process including unfrozen and frozen dough was studied. A method was developed for the separation and quantification of tea catechins in GTE, dough, and bread samples using a RP-HPLC system. The separation system consisted of a C18 reversed-phase column, a gradient elution system of water/methanol and formic acid, and a photodiode array UV detector. Tea catechins were detected at 275 nm. GTEs at 50, 100, and 150 mg per 100 g of flour were formulated. The results obtained showed that green tea catechins were relatively stable in dough during freezing and frozen storage at -20 degrees C for up to 9 weeks. There were no further detectable losses of tea catechins in bread during a storage of 4 days at room temperature. It was also revealed that (-)-epigallocatechin gallate (EGCG) and (-)-epigallocatechin (EGC) were more susceptible to degradation than (-)-epicatechin gallate (ECG) and (-)-epicatechin (EC). (-)-EGCG and (-)-ECG were normally selected as the quality indices of green tea catechins, and their retention levels in freshly baked bread were ca. 83 and 91%, respectively. One piece of bread (53 g) containing 150 mg of GTE/100 g of flour will provide 28 mg of tea catechins, which is approximately 35% of those infused from one green tea bag (2 g).     

Inhibitory effects of tea catechins and O-methylated derivatives of (-)-epigallocatechin-3-O-gallate on mouse type IV allergy

The inhibitory effects of tea catechins, the O-methylated derivatives of (-)-epigallocatechin-3-O-gallate (EGCG), and the polyphenol extracts from tea leaves (Camellia sinensis L.) on oxazolone-induced type IV allergy in male ICR mice were investigated. Four major tea catechins and two O-methylated derivatives, (-)-epigallocatechin-3-O-(3-O-methyl)gallate (EGCG3' 'Me) and (-)-epigallocatechin-3-O-(4-O-methyl)gallate (EGCG4' 'Me), showed significant inhibitory effects on mouse type IV allergy after a percutaneous administration at a dose of 0.13 mg/ear. Among tea catechins, the compounds including galloyl moieties, such as EGCG and (-)-epicatechin-3-O-gallate (ECG), showed the strongest inhibitory activities on mouse type IV allergy. The inhibitory activities of EGCG3' 'Me and EGCG4' 'Me were higher than that of EGCG at a dose of 0.05 mg/ear. Polyphenol extract from tea leaves of Benihomare cultivar, which includes EGCG3' 'Me, strongly inhibited mouse type IV allergy after percutaneous administration in comparison with that from Yabukita cultivar, which does not include EGCG3' 'Me, at doses of 0.05 and 0.13 mg/ear. EGCG3' 'Me is thought to contribute, at least in part, to the inhibitory ability of Benihomare tea leaves on mouse type IV allergy. EGCG and the polyphenol extracts from Benihomare and Yabukita tea leaves also inhibited mouse type IV allergy by oral administration at 1 h before the sensitization and at 1 h before the challenge with oxazolone. Therefore, daily intake of tea drinks could have potential to prevent type IV allergy.     

Epicatechin-3-O-(3″-O-methyl)-gallate content in various tea cultivars (Camellia sinensis L.) and its in vitro inhibitory effect on histamine release

It has been reported that epigallocatechin-3-O-(3″-O-methyl)-gallate (EGCG3″Me) and the EGCG3″Me-rich green tea ( Camellia sinensis L.) cultivar 'Benifuuki' exhibit antiallergic effects. The objective of this study was to investigate the effect of various tea leaf catechins on histamine release from murine bone marrow mast cells (BMMC). At a dose of 50 μg/mL, the rank order of histamine release inhibition was observed to be epicatechin-3-O-(3″-O-methyl)-gallate (ECG3″Me) > gallocatechin-3-O-(3″-O-methyl)-gallate (GCG3″Me) > EGCG3″Me > gallocatechin-gallate (GCG) > catechin-gallate (CG) > EGCG > epicatechin-gallate (ECG) > epigallocatechin (EGC) > gallocatechin (GC). Of the various tea cultivars analyzed by HPLC, the greatest content of ECG3″Me was found in the third crop of 'Benifuuki' (1.05% dry weight). Moreover, ECG3″Me content was positively correlated with EGCG3″Me content in 'Benifuuki' tea leaves. In an assay of mixtures of ECG3″Me and EGCG3″Me, inhibitory activity (50 μg/mL in total) was increased as the content of ECG3″Me increased. This suggests that ECG3″Me might link to the antiallergic effect of 'Benifuuki' tea, as has been reported for EGCG3″Me.     

Kinetics of reduction of ferrylmyoglobin by (-)-epigallocatechin gallate and green tea extract

The hypervalent heme pigment ferrylmyoglobin, a potential prooxidant in muscle tissue and meat, is efficiently reduced by epigallocatechin gallate (EGCG) from green tea and by green tea polyphenol extract (GTP) in neutral or moderately acidic aqueous solution (0.16 M NaCl) to yield metmyoglobin in two parallel processes. The second-order rate constant for direct reduction at pH 7.4 and 25 degrees C was found to have the value 1170 +/- 83 M(-1).s(-1) and activation parameters DeltaH(#) = 70.6 +/- 7.2 kJ.mol(-1) and DeltaS(#) = 50.7 +/- 24.1 J.mol(-1).K(-1) for EGCG and the value 2300 +/- 77 M(-1).s(-1) and parameters DeltaH(#) = 60.6 +/- 2.6 kJ.mol(-1) and DeltaS(#) = 23 +/- 9 J.mol(-1).K(-1) for GTP (based on EGCG concentration). For decreasing pH, the rate increased moderately due to a parallel reduction of protonated ferrylmyoglobin. At physiological pH, EGCG is more efficient in deactivating ferrylmyoglobin than other plant phenols investigated, and the relatively high enthalpy and positive entropy of activation suggest an outer-sphere electron transfer mechanism. The interaction between EGCG and other tea catechins in GTP could be responsible for the even stronger ability for GTP to deactivate ferrylmyoglobin.     

Epimerization of tea catechins and O-methylated derivatives of (-)-epigallocatechin-3-O-gallate: relationship between epimerization and chemical structure

Epimerization at C-2 of O-methylated catechin derivatives and four major tea catechins were investigated. The epimeric isomers of (-)-epicatechin (I), (-)-epicatechin-3-O-gallate (II), (-)-epigallocatechin (III), (-)-epigallocatechin-3-O-gallate (IV), and (-)-epigallocatechin-3-O-(3-O-methyl)gallate (V) in green tea extracts increased time-dependently at 90 degrees C. The epimerization rates of authentic tea catechins in distilled water are much lower than those in tea infusion or in pH 6.0 buffer solution. The addition of tea infusion to the authentic catechin solution accelerated the epimerization, and the addition of ethylenediaminetetraacetic acid, disodium salt (Na(2)EDTA) decreased the epimerization in the pH 6.0 buffer solution. Therefore, the metal ions in tea infusion may affect the rate of epimerization. The proportions of the epimers to authentic tea catechins [III, IV, V, and (-)-epigallocatechin-3-O-(4-O-methyl)gallate (VI)] in pH 6.0 buffer solution after heating at 90 degrees C for 30 min were 42.4%, 37.0%, 41.7%, and 30.4%, respectively. These values were higher than those of I and II (23.5% and 23.6%, respectively). The O-methylated derivatives at the 4'-position on the B ring of IV and VI were hardly epimerized. These results suggest that the hydroxyl moiety on the B ring of catechins plays an important role in the epimerization in the order 3',4',5'-triol type > 3',4'-diol type > 3',5'-diol type.     

Degradation kinetics of catechins in green tea powder: effects of temperature and relative humidity

The stability of catechins in green tea powders is important for product shelf life and delivering health benefits. Most published kinetic studies of catechin degradation have been conducted with dilute solutions and, therefore, are limited in applicability to powder systems. In this study, spray-dried green tea extract powders were stored under various relative humidity (RH) (43-97%) and temperature (25-60 °C) conditions for up to 16 weeks. High-performance liquid chromatography (HPLC) was used to determine catechin contents. Catechin degradation kinetics were affected by RH and temperature, but temperature was the dominant factor. Kinetic models as functions of RH and temperature for the individual 2,3-cis-configured catechins (EGCG, EGC, ECG, and EC) were established. The reaction rate constants of catechin degradation also followed the Williams-Landel-Ferry (WLF) relationship. This study provides a powerful prediction approach for the shelf life of green tea powder and highlights the importance of glass transition in solid state kinetics studies.     

Effects of tea catechins on the ERE-regulated estrogenic activity

Tea catechins exert many biological effects, including anticancer and antibacterial activities. Also, it is reported that some plant flavonoids exhibit estrogenic activity. In this study, we investigated estrogenic or antiestrogenic activities of catechins in HeLa cells transiently transfected with an estrogen response element (ERE)-regulated luciferase reporter and an estrogen receptor (ER) alpha or ERbeta expression vector. Catechins alone did not induce luciferase (luc) activity in either of the ERs. Addition of 17beta-estradiol (E2) plus epicatechin gallate (ECG) or epigallocatechin gallate (EGCG) at 5 x 10(-6) M resulted in significant decreases in the ERalpha-mediated luc activity compared with that of E2 alone. On the contrary, lower concentrations significantly increased the E2-induced luc activity. Similar effects were observed with tamoxifen. The ERbeta-mediated estrogenic activities were stimulated by catechins. In conclusion, some catechins, particularly EGCG, were antiestrogenic for ERalpha at higher doses, and co-estrogenic for ERalpha at lower doses and for ERbeta. The lower doses were found in human plasma after tea-drinking. In addition, some catechins may be antiendocrine disruptors because they suppressed bisphenol A-induced luc activities.     

Different effects of five catechins on 6-hydroxydopamine-induced apoptosis in PC12 cells.

Five catechins [(-)-epigallocatechins gallate (EGCG), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC), (-)-epicatechin (EC), and (+)-catechin (C)] were compared with regard to their effects on 6-hydroxydopamine (OHDA)-induced apoptosis in PC12 cells--the vitro model of Parkinson's disease. Measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, 6-OHDA inhibited cell viability in a time- and concentration-dependent manner. When PC12 cells were pretreated with the five catechins for 30 min before exposure to 250 microM 6-OHDA, MTT results showed that the five catechins had different effects: EGCG and ECG had obvious concentration-dependent protective effects at 50-400 microM; EC and (+)-C had almost no effects; and EGC especially decreased cell viability. Catechins also had different effects on apoptotic morphology. Only 200-400 microM EGCG and ECG kept cells adhering well. When pretreated with other catechins at any concentration, PC12 cells became round and some of them were detached as when treated with 6-OHDA. In addition, typical apoptotic characteristics of PC12 cells were determined by fluorescence microscopy, flow cytometry, and DNA fragment electrophoresis after the cells were treated with 250 microM 6-OHDA for 24 h or pretreated with catechins before it. Preincubation with 200-400 microM EGCG and ECG led to significant inhibitory effects against PC12 cell apoptosis, as shown by flow cytometry. The other catechins have little protective effect. Therefore, at 200-400 microM, the classified protective effects of the five catechins were in the order ECG > EGCG > EC > (+)-C > EGC. The data also indicated that EGCG and ECG might be potent neuroprotective agents for Parkinson's disease. The results of fluorescence microscopy and DNA fragment analysis supported the conclusion.     

Green tea polyphenols inhibit metalloproteinase activities in the skin,muscle, and blood of rainbow trout

We have investigated the inhibitory effects of polyphenols from natural products, such as green tea, bilberry, grape, ginkgo, and apple, on rainbow trout gelatinase activities. Gelatinases from the skin, muscle, and blood of rainbow trout contained serine proteinase, metalloproteinase, and other proteinase activities as measured by gelatin zymography. The polyphenols of green tea caused the strong inhibition of some gelatinase activities when compared with those of the other products. This inhibition was quite similar to that of metalloproteinase by ethylenediaminetetraacetic acid, suggesting that the effects of green tea polyphenols on proteinase activities are specific for metalloproteinases. The major catechins of green tea polyphenols were then separated and identified by reverse-phase chromatography to be (-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin, (-)-epicatechin gallate, and (-)-epicatechin. The effects of these catechins on gelatinase activities were examined; the most potent inhibitor of metalloproteinase activities was found to be EGCG. These results have indicated that green tea polyphenols including EGCG are useful for regulating metalloproteinase activities of fish meat.     

Regeneration of alpha-tocopherol in human low-density lipoprotein by green tea catechin.

Oxidative modification of low-density lipoproteins (LDL) may play an important role in the development of atherosclerosis. alpha-Tocopherol functions as a major antioxidant in human LDL. The present study was to test whether green tea catechins (GTC) would protect or regenerate alpha-tocopherol in human LDL. The oxidation of LDL incubated in sodium phosphate buffer (pH 7.4, 10 mM) was initiated by addition of 1.0 mM of 2,2'-azobis(2-amidinopropane) dihydrochloride at 40 degrees C. It was found that alpha-tocopherol was completely depleted within 1 h. Under the same experimental conditions, the longjing GTC extracts demonstrated a dose-dependent protective activity to alpha-tocopherol in LDL at concentrations ranging from 2 to 20 microM. Four pure epicatechin derivatives showed varying protective activity against depletion of alpha-tocopherol in LDL with (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG) being less effective than (-)-epicatechin (EC) and (-)-epicatechin gallate (ECG). The results showed that addition of longjing GTC extracts, EC, ECG, and EGCG at 5, 10, and 15 min to the incubation mixture demonstrated a gradual regeneration of alpha-tocopherol in human LDL.     

茶叶添加方式对酿造啤酒理化特性及感官品质的影响

在啤酒酿造工艺的煮沸和主发酵阶段分别添加乌龙茶,探讨茶叶不同添加方式对啤酒理化特性、抗氧化能力、啤酒贮存稳定性以及感官特性的影响。结果显示,与未添加茶叶的啤酒产品(对照组CG)相比,在煮沸阶段(煮沸添加组BG)和主发酵阶段(主发酵添加组MG)分别添加0.3g/L的茶叶均提高了酵母发酵速率;添加茶叶的两个茶啤酒产品(煮沸添加组和主发酵添加组)的DPPH自由基清除能力分别提升至82.74%和89.21%、ABTS+自由基清除能力分别提升至41.53%和51.49%、铁离子还原能力分别提升至36.49和43.83 mg/L,且成品茶啤酒贮藏期间的抗老化能力提高;茶啤酒中总酚以及儿茶素(EGC、C、EGCG、EC、GCG、ECG)和咖啡碱(CAF)含量升高,其中,主发酵添加组茶啤酒样品总酚和EGCG含量显著高于对照组和煮沸添加组啤酒(P0.05),分别达到734.40和8.43 mg/L。进一步的感官品评结果显示添加茶叶提高了啤酒产品的茶香气和茶滋味,其中主发酵添加组啤酒的茶香气、茶滋味及酒体协调性最好。由此可知,在啤酒酿造工艺中添加茶叶提高了酵母发酵速率,增强了啤酒中酚类物质含量及其抗氧化和抗老化性能,同时也为啤酒增添了新的茶风味产品。     

The apoptotic effect of green tea (-)-epigallocatechin gallate on 3T3-L1 preadipocytes depends on the Cdk2 pathway

This study was designed to investigate the effect of green tea catechins, especially (-)-epigallocatechin gallate (EGCG), on the apoptosis of 3T3-L1 preadipocytes. Preadipocyte apoptosis as indicated by formation of DNA fragments was induced by EGCG in dose-dependent manners. While EGCG was demonstrated to decrease Cdk2 expression and activity and increase caspase-3 activity, overexpression of Cdk2 and treatment with the caspase-3 inhibitor respectively prevented preadipocytes from induction of DNA fragmentation and caspase-3 activity by doses of 100-400 muM of EGCG. This suggests the Cdk2- and caspase-3-dependent apoptotic effects of EGCG. Moreover, EGCG was more effective than EC, ECG, and EGC in changing the apoptotic signals. Results of this study may relate to the mechanism by which EGCG modulates body weight.     

Interaction of environmental moisture with powdered green tea formulations: effect on catechin chemical stability

Green tea and tea catechins must be stable in finished products to deliver health benefits; however, they may be adversely affected by tea processing/storage conditions and the presence of other components. The objective of this study was to determine the effects of storage relative humidity (RH) and addition of other ingredients on catechin stability in simulated dry beverage mixtures. Samples of green tea powder alone and mixed with sucrose, citric acid, and/or ascorbic acid were prepared and stored in desiccators at 22 degrees C and 0-85% RH for up to 3 months. Epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate were determined by high-performance liquid chromatography (HPLC). Formulation and the interaction of formulation and RH significantly promoted catechin degradation ( P < 0.0001). The chemical degradation of total and individual catechins in green tea powder formulations was significantly increased ( P < 0.0001) by exposure to increasing RH, and the degradation was exacerbated at > or = 58% RH by the presence of powdered citric acid and at > or = 75% RH by the presence of ascorbic acid. Catechins degraded the most in formulations containing both acids. Although catechin chemical stability was maintained at < or = 43% RH in all samples stored at 22 degrees C for 3 months, caking was observed in samples at these relative humidities. These results are the first to demonstrate that addition of other dry components to tea powders may affect catechin stability in finished dry blends and highlight the importance of considering the complex interplay between a multicomponent system and its environment for developing stable products.     

Stopped-flow kinetic study of the aroxyl radical-scavenging action of catechins and vitamin C in ethanol and micellar solutions

Kinetic study of the aroxyl radical-scavenging action of catechins (epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), and epigallocatechin gallate (EGCG)) and related compounds (methyl gallate (MG), 4-methylcatechol (MC), and 5-methoxyresorcinol (MR)) has been performed. The second-order rate constant ( k s) for the reaction of these antioxidants with aroxyl radical has been measured in ethanol and aqueous Triton X-100 micellar solution (5.0 wt %). The k s values decreased in the order of EGCG > EGC > MC > ECG > EC > MG > MR in ethanol, indicating that the reactivity of the OH groups in catechins decreased in the order of pyrogallol B-ring > catechol B-ring > gallate G-ring > resorcinol A-ring. The structure-activity relationship in the free radical-scavenging reaction by catechins has been clarified by the detailed analyses of the pH dependence of k s values. From the results, the p K a values have been determined for catechins. The monoanion form at catechol B- and resorcinol A-rings and dianion form at pyrogallol B- and gallate G-rings show the highest activity for free radical scavenging. It was found that the free radical-scavenging activities of catechins are 3.2-13 times larger than that of vitamin C at pH 7.0.     

Determination of tea components with antioxidant activity

Levels of essential elements with antioxidant activity, as well as catechins, gallic acid, and caffeine levels, in a total of 45 samples of different teas commercialized in Spain have been evaluated. Chromium, manganese, selenium, and zinc were determined in the samples mineralized with HNO(3) and V(2)O(5), using ETAAS as the analytical technique. The reliability of the procedure was checked by analysis of a certified reference material. Large variations in the trace element composition of teas were observed. The levels ranged from 50.6 to 371.4 ng/g for Cr, from 76.1 to 987.6 microg/g for Mn, from 48.5 to 114.6 ng/g for Se, and from 56.3 to 78.6 ng/g for Zn. The four major catechins [(-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epicatechin (EC)], gallic acid (GA), and caffeine were simultaneously determined by a simple and fast HPLC method using a photodiode array detector. In all analyzed samples, EGCG ranged from 1.4 to 103.5 mg/g, EGC from 3.9 to 45.3 mg/g, ECG from 0.2 to 45.6 mg/g, and EC ranged from 0.6 to 21.2 mg/g. These results indicated that green tea has a higher content of catechins than both oolong and fermented teas (red and black teas); the fermentation process during tea manufacturing reduces the levels of catechins significantly. Gallic acid content ranged from 0.039 to 6.7 mg/g; the fermentation process also elevated remarkably gallic acid levels in black teas (mean level of 3.9 +/- 1.5 mg/g). The amount of caffeine in the analyzed samples ranged from 7.5 to 86.6 mg/g, and the lower values were detected in green and oolong teas. This study will be useful for the appraisal of trace elements and antioxidant components in various teas, and it will also be of interest for people who like drinking this beverage.