Bioactive compounds and antioxidant capacity of yellow Yinzhen tea affected by different extraction conditions

摘要

Tea is one of the most popular beverages consumed worldwide. Polyphenols in tea contribute to its health benefits possessing high antioxidant, anticarcinogenic and antiallergic activity. The aim of this study was to examine the effect of ethanol concentration, tea forms and storage duration on polyphenols and methylxanthines composition, as well as antioxidant capacity of yellow Yinzhen tea. Total polyphenol, flavonoid concentration and antioxidant capacity were measured spectrofotometrically, while individual catechins and methylxanthines were identified and quantified using high performance liquid chromatography with photodiode array detector (HPLC-PDA). •DPPH (reduction of 1, 1-diphenyl-2-picrylhidrazyl), ABTS•+ (reaction of 2, 2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) and FRAP (reaction with iron(III)tripyridyltriazine) assays were applied to determine the antioxidant capacity. The highest polyphenol concentration and antioxidant capacity were determined in 75% ethanol tea extract stored for 24-hours. The application of lower ethanol concentration (50% or less) was the most efficient in individual catechins extraction. The most abundant catechin is epigallocatechin gallate, EGCG (12.60 ± 0.1 - 416.01 ± 2.70 mg•l-1), followed by the epigallocatechin, EGC (1.59 ± 0.10 - 264.92 ± 2.43 mg•l-1).