Determination of catechins and flavonol glycosides in Chinese tea varieties (original) (raw)
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A Survey Of Catechins Contents Of Different Green Teas Currently Available In The UK Market
مجلة ميسان للدراسات الأكاديمية, 2017
The level content of the main flavanols in green tea (i.e. epi-structured catechins) in regular commercial green tea bags commonly consumed in the United Kingdom (UK)have been examined using reversed-phasehigh-pressure liquid chromatography (RP-HPLC). Tea bags were purchased from different local supermarkets in the UK and extracted with natural mineral water at temperature 100°C for 9 minutes at the pre-adjusted pH 4.The level of four catechins (Epistructured)for the fourteen types of green teawere separated and determinedby HPLC analysis,i.e. ()-epigallocatechin (EGC), ()-epicatechin (EC), ()epigallocatechin-3-gallate (EGCG) and ()-epicatechingallate (ECG). The standard graphs were validated using certified reference catechins supplied by the Laboratory of the Government Chemist (LGC).The levels of total catechins and oxygen radical absorbance capacity (ORAC) values varied from 96.38 to 205.03 mg/g, 1097.30-3421.14Trolox equivalents/g tea bags for fourteen types of green teas respectively.It was evident from the results of this study that there was significant linear and positive correlation (r = 0.932, df = 13, p < 0.05) is found to 05 exist between the total catechins contents and ORACvalues.It couldbe concluded that the developed HPLC method gave reliable results for catechins measurementscoupled to this; the well-known ORAC assay was successfully adapted to measure the antioxidant capacity of the green tea extracts throughout this study. Moreover, the higher the level of catechins the greater is the antioxidant capacity of the tea. However,the differences between the studied brands are owing to production, shelf life and storage conditions.
GSC Biological and Pharmaceutical Sciences, 2021
Background: Tea is a refreshing drink that contains polyphenol compounds, namely catechins that are used for medicine and cosmetics. This study was to assess the content of catechin compounds in green tea, oolong and black tea products from Indonesia, China and Taiwan. Methods: Some tea products are brewed at varying temperatures (75±2; 85±2 and 95±20 C) and times (5; 10 and 15 minutes). Identification of catechin compounds was carried out using chemical reagents and UV spectrophotometry. The level of cathecin in tea products were analyzed by spectrophotometer at 280 nm wavelength. Results: The results obtained indicate that green tea, oolong tea and black tea contain epigallocatechin-3-gallate (EGCG) compounds according to the color change based on chemical reagents and for UV spectrum analysis which has λmax in the range 268-274 nm. The results of quantitative tests using UV-Vis spectrophotometry showed that the green tea samples gave the highest levels of catechins followed by oo...
Food Chemistry, 2013
Black (aerated) and green (unaerated) tea products, processed from 10 green and 18 purple leaf coloured cultivars of Kenyan origin, and two tea products, from the Japanese cultivars, Yabukita and Yutakamidori, were assayed for total polyphenols (TP) content, individual catechin profiles and in vitro antioxidant capacity (AA). In addition, the phenolic content of the tea products was determined using the Folin-Ciocalteu phenol reagent. Catechin fractions were identified using reverse phase high performance liquid chromatography (HPLC) with a binary gradient elution system. The AA% of the tea products was determined using a 2,2 0-diphenyl picrylhydrazyl (DPPH) radical assay method. The results showed that TPs, catechin profiles and antioxidant activities were significantly (p 6 0.05) higher in unaerated than in aerated teas. Tea products from the purple leaf coloured tea cultivars had levels of TPs, total catechin (TC) and antioxidant activities similar to those from the green leaf coloured cultivars, except for teas from the Japanese cultivars that were very low in the assayed parameters. Caffeine content was significantly (p 6 0.05) lower in products from the purple leaf coloured cultivars than in those from the green leaf coloured tea cultivars. Antioxidant activity (%) was higher in tea products from the Kenyan germplasm than in those from the Japanese cultivars. Antioxidant potency of tea products was significantly (r = 0.789 ⁄⁄ , p 6 0.01) influenced by the total anthocyanin content of the purple leaf coloured cultivars. Cyanidin-3-O-glucoside was the anthocyanin most highly correlated with AA% (r = 0.843 ⁄⁄ , p 6 0.01 in unaerated tea). Total catechins in the unaerated products from the green leaf coloured tea cultivars were also significantly correlated with antioxidant capacity (r = 0.818 ⁄⁄ , p 6 0.01). Results from this study suggest that the antioxidant potency of teas is dependent on the predominant flavonoid compound, the type of tea cultivar and the processing method.
Journal of Agricultural and Food Chemistry, 2007
Oolong tea manufactured via a semifermentation process possesses a taste and color somewhere between green and black teas. Alteration of constituents, particularly phenolic compounds, in the infusion of oolong tea resulting from its manufacture, was analyzed by high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry. The identified constituents contained 2 alkaloids, 11 flavan-3-ols, 8 organic acids and esters, 11 proanthocyanidin dimers, 3 theaflavins, and 22 flavonoid glycosides, including 6 novel acylated flavonol glycosides. The tentative structures of these 6 novel compounds were depicted according to their mass fragmentation patterns in MS n (n) 1-4). In comparison with caffeine as an internal standard, relative contents of the constituents in the infusions of fresh tea shoot and different oolong tea preparations were examined. Approximately, 30% catechins and 20% proanthocyanidins were oxidized during the manufacture of oolong tea from fresh tea shoots, and 20% of total flavonoids were decomposed in a follow-up drying process. Gallocatechin-3-O-gallate and theaflavins putatively produced in the semifermentation process of oolong tea were not detected in fresh tea shoots, and the majority of theaflavins were presumably transformed into thearubigins after drying.
Most previous studies have been focused on the variation of tea chemical composition by fermentative processes as well as different cultivars and regions. The detailed changes of flavonoid profiles were described for the first time by each processing step of green and black tea leaves in this study. A total of 24 flavonoid derivatives including catechins, theaflavins, and flavonols were separated and identified from the tea samples based on UPLC-DAD-QToF/MS data and constructed library. Among these, the fragmentation pathway of theaflavins was proposed specifically in positive ionization mode for structural interpretation. During leaf processing, the individual flavonols were changed as diverse patterns according to their aglycone types and glycosylated forms, but their total content showed a slight difference. EGCG and ECG were increased after roasting approximately twofold higher than that of fresh leaves (EGCG, 2709.5 →6085.6; ECG, 1548.0 →2318.2 mg/100 g dry weight, respectively) in green tea while considerably decreased their contents due to oxidation and conversion to theaflavins after fermentation during black tea processing. Especially, the drying steps also found to be factor to influence positively to increase the flavonoid contents in both tea processing. Therefore, this result indicated that detailed conditions of each processing step played important roles in changing the flavonoid profiles from tea leaves.
Journal of Chromatography A, 1998
A high-performance liquid chromatography method employing diode array detection was developed to determine levels of the major catechins present in black, green, and Jasmine tea infusions. Reversed-phase separations were performed on a C 18 column using three gradients: acetonitrile-acetate buffer, methanol-acetate buffer, and acetonitrile-acetate buffer with ascorbic acid. The identities of the tea catechins were established by comparing absorbance spectra and retention times to reference standards chromatographed under identical conditions. Epicatechin, epigallocatechin, epicatechin gallate, and 21 epigallocatechin gallate were found in all the tea infusions examined, ranging in concentration from 1-13 mg dl. These levels indicate that even moderate tea consumption can contribute a substantial quantity of flavanols to the diet. Although some differences between the three brewed teas were evident, all were comparably good sources of these catechins. 1998 Published by Elsevier Science B. V.
Catechin-like antioxidative potential of selected tea products
Herba Polonica, 2012
The presented study was aimed to establish the levels of antioxidative potential of five types of tea (white, red, green, black and blue/turquoise) originating from different geographical regions. Furthermore, the content and qualitative composition of phenolics in aqueous infusions of the tested tea products was compared. The highest antioxidant activity against DPPH• free radical was found in extracts obtained from white teas, whereas the lowest in extracts from red teas. Moreover, the highest total phenolics content was shown in the extracts prepared from the white teas. In addition, the HPLC analysis allowed to identify the following catechin derivatives in the tea extracts: (+)-catechin, (-)-epicatechin, (-)-epigallocatechin and (-)-epicatechin gallate. Simultaneously, it was shown that the dominant compound in extracts from the all tested teas was (+)-catechin.
Study of flavonoids and phenolic acids in green tea leaves
Current issues in pharmacy and medicine: science and practice, 2021
The aim of work is study qualitative composition and quantitative content of flavonoids and phenolic acids in green tea leaves. Material and methods. The object of the study was green tea leaves, which were collected in Anhui Province, China. The analysis of 60 % ethanolic extract from green tea leaves was performed by high-performance liquid chromatography using a Prominence LC-20 Shimadzu chromatographic system (Japan) with an SPD-20AV spectrophotometric detector, an Agilent Technologies Microsorb-MV-150 column (reversed-phase, C18 modified silica gel, length – 250 mm, diameter – 4.6 mm, particles size – 5 μm). Identification of substances in the extract was carried out by comparing the retention time and the spectral characteristics of the test substances with the same characteristics of the reference standards. Results. 13 compounds were identified and determined by high-performance liquid chromatography. Among flavonoid aglycones quantitatively dominated by quercetin (0.35 %),...
Diversity of Catechin in Northeast Indian Tea Cultivars
The Scientific World Journal, 2012
Tea (Camellia sinensis L.) leaf contains a large amount of catechins (a group of very active flavonoids) which contribute to major quality attributes of black tea. Based on morphological characters tea plants were classified as Assam, China, and Cambod varieties. The present study is an attempt for biochemical fingerprinting of the tea varieties based on catechin composition in green leaf of cultivars grown in Northeast India. Assam variety cultivars contained the highest level of catechins followed by Cambod and China. The average catechin contents were 231 ± 7 mg g −1 , 202 ± 5 mg g −1 , and 157 ± 4 mg g −1 of dry weight of green leaf for Assam, Cambod, and China cultivars, respectively. Among the individual catechins the variations in epigallocatechin gallate (EGCG) and epigallocatechin (EGC) were the most prominent among the varieties. High EGC content was found to be a characteristic of Assam variety which was further corroborated through multivariate analysis.
Phenolic compounds like catechin undergo spontaneous natural oxidation producing poly-phenols or tannins by aerial O 2 , heat or exposure to UV radiation. Using synthetic catechin as standard, its levels in dry leaves is assessed spectrophotometrically at 260 nm (57 mg / g) and also by the F-C reagent (76 mg / g) for both green and black teas which are found to be the same. Extraction of dry commercial leaves by EtOH in the dark at RT shows two distinct identical peaks (λ max) at 260 and 400 nm for both green and black whereas synthetic catechin under similar condition shows only one (λ max = 260 nm), confirming the presence of pre-oxidized phenolics in extracts. The EtOH extracts if diluted and incubated at different pH, shows identical spectral pattern having λ max at 260 and 360-380 nm except at pH 4.7. Noticeably, λ max is shifted backward from 400 nm (in EtOH) to 360 or 380 nm in the aqueous buffer at normal or higher pH. At pH 4.7 the native catechin shows a single peak at 260 nm but the EtOH extracts of both leaves display λ max at 260 nm with distinctive additional shoulder at 360 nm. The shoulder is turned to whole peak if the acidity is lowered to pH 7.5 or further. The analysis by HPLC with detection at 440 nm of green and black tea extracts shows major peak comprising of ~57 and 73% area out of the total accompanied by other components having the same retention time (~9.2 min) which is an indication of the presence of pre-oxidized poly-phenolics in both. As per conclusion, the study insists to believe that in addition to total content, the level of oxidation are about the same for both teas and the event of oxidation takes place during commercial processing of the leaves but not in course of experimentation.