Antioxidative Chemical Constituents from the Stems of Cleyera japonica Thunberg

Chemical investigation to identify the antioxidative constituents from the stems of a tree Cleyera japonica Thunb. resulted in the isolation of seven compounds: catechin (1), catechin 3-O-alpha-L-rhamnopyranoside (2), epicatechin (3), taxifolin (4), taxifolin 3-O-alpha-L-arabinopyranoside (5), taxifolin 3-O-alpha-L-rhamnopyranoside (6) and proanthocyanidin A-1 (7). These isolates were studied for their scavenging activities against DPPH radical, hydroxyl radical and superoxide anion radicals using spectrophotometry and/or electron spin resonance. All isolates 1-7 exhibited more potent DPPH radical inhibition activities than the positive control, ascorbic acid. In the hydroxyl radical scavenging test, compound 7 (SC50 301.6 mu M) showed potent activity higher than ascorbic acid (SC50 859.7 mu M). All of the compounds 1-7 exhibited comparable activities to ascorbic acid for superoxide anion radical scavenging. These results demonstrated that C. japonica stem extracts could be potentially used as antioxidative agents in food or cosmetic applications.