In this study, the relationship between the catechin content and antioxidant capacity of the tea extract, a natural food additive, was investigated to establish the quality standards based on the antioxidant capacity. The antioxidant activity was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The antioxidant capacities were detected in 13 kinds of tea extracts among the tested 14 kinds of them. A correlation was found between the total amount of catechins (C, EC, GC, EGC, Cg, ECg, GCg, and EGCg) and the antioxidant capacity (r = 0.975, n = 13, p ‹ 0.01). In addition, the contribution ratio of all kinds of catechins in the tea extract to the antioxidant capacity was 90%. These results suggest that the DPPH assay is a useful method to evaluate the antioxidant capacity in the tea extract for establishing the quality standards.
