Total Polyphenols, total Catechins content and DPPH free radical scavenger activity of several types of Vietnam commercial green tea

Abstract

Thirty types of commercial Vietnamese-brand teas (21 green teas, 5 black teas, 4 oolong teas) in Ho Chi Minh city were investigated for total polyphenols content (TPC- acid gallic equivalent), total catechins content (TCC-catechin equivalent) and DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenger activity (RSA - Vitamine C equivalent). It was found that green tea had the highest TPC (15.06  0.53 ppm), TCC (7.33  1.71 ppm) and RSA (288  23 mg) in three grams dried tea, higher than those of oolong tea, whereas black tea had the lowest TPC, TCC, RSA. However, high inconsistency and high deviation from mean values were observed within green tea group. Unexpectedly, several green tea types had low TPC, TCC, and RAC, even as low as those of black tea. This evidence demonstrated the instability and unevenness of green tea quality in Vietnam market.