Correlation of major components and radical scavenging activity of commercial tea drinks in Taiwan

Correlation of major components with free radical scavenging activities of 27 commercial tea drinks prepared from green, Oolong, and black teas in Taiwan were investigated. Green tea drinks contained the highest level of total catechins including epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin (EC), epicatechin gallate (ECG), and gallocatechin gallate (GCG), while these components were low in black tea drinks and moderate in Oolong tea drinks. EGC and EGCG were the major catechins in the three types of tea drinks, and gallic acid showed the highest abundance in black tea drinks. Caffeine concentrations were comparable in the three types of tea drinks. All black tea drinks contained sugars, and sucrose was the main sweetener added. The scavenging abilities against l,l-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radicals were used to determine the antioxidant potential of tea drinks, and the ranked order of potency was green tea > Oolong tea > black tea. Total phenolics, total catechins, and EGC of tea drinks were positively and significantly (r > 0.8) correlated to the scavenging abilities against DPPH and ABTS radicals. Our results show that green tea drinks have higher free radical scavenging activity than black and Oolong tea drinks may be related to their high levels of total phenolics and catechins.