Relationship between antioxidative activity estimated by XYZ-dish method and catechin concentration in commercially available tea drinks - (Study on antioxidative assay using photon detection - Part II)

A relationship between antioxidative activity and catechin concentration wa s investigated for estimating antioxidative potency of commercially availab le tea drinks by using the XYZ-dish method. Antioxidative activity of canne d drinks determined by the XYZ-dish method increased in the following order : other teas < oolong teas < green teas. The antioxidative activity of tea infusions extracted from green tea leaves was markedly stronger than that of canned tea drinks. Epigallocatechin gallate (EGCg), gallocatechin gallat e and epigallocatechin (EGC) were found to have stronger antioxidative acti vities. It was suggested that the presence a hydroxyl group at 5'-position of B ring and the total number of aromatic hydroxyl groups contributed to t he increase in activity. The concentration of catechin compounds in tea dri nks showed different levels among the tea samples examined, particularly it was markedly higher in the tea infusions than in canned tea drinks. High c ontents of EGCg and EGC were detected in most of the tea drinks with strong er antioxidative activities, suggesting that the two catechins mainly affec ted the antioxidative activity of tea drinks. Furthermore, it was confirmed that the antioxidative activity was dependent on the catechin concentratio n, because a significant high correlation was found between the activities and the total concentration of eight catechins in the tea drinks. These res ults demonstrated that the XYZ-dish method was useful as an antioxidative a ssay of tea drinks containing polyphenolic antioxidant activity.