ANTIOXIDANT ACTIVITY OF GREEN TEA CATECHINS IN A β-CAROTENE-LINOLEATE MODEL SYSTEM

A crude mixture of catechins was isolated from Chinese green tea leaves using a hot water extraction. Individual catechins were then separated by chromatographic means using Sephadex LH-20 followed by semi-preparative HPLC. The antioxidant activity of crude and individual catechins was then determined in a β-carotene-linoleate model system. Results indicated that (−)-epicatechin-3-gallate (ECG) possessed the strongest antioxidative activity and (−)-epigallocatechin (EGC) showed the weakest effect. The antioxidative efficacy of (−)-epicatechin (EC) and (−)-epigallocatechin-3-gallate (EGCG) was similar and in between those of ECG and EGC. Furthermore, the antioxidant activity of a reconstituted catechin mixture in the proportions present in the crude extract was lower than that of the crude mixture itself, thus indicating that noncatechin components in the mixture possessed their own antioxidant activity or acted synergistically with the catechins.