Epicatechin and its in vivo metabolite, 3 '-O-methyl epicatechin, protect human fibroblasts from oxidative-stress-induced cell death involving caspase-3 activation

There is considerable current interest in the cytoprotective effects of nat ural antioxidants against oxidative stress. In particular, epicatechin, a m ajor member of the flavanol family of polyphenols with powerful antioxidant properties in vitro, has been investigated to determine its ability to att enuate oxidative-stress-induced cell damage and to understand the mechanism of its protective action. We have induced oxidative stress in cultured hum an fibroblasts using hydrogen peroxide and examined the cellular responses in the form of mitochondrial function, cell-membrane damage, annexin-V bind ing and caspase-3 activation. Since one of the major metabolites of epicate chin in vivo is 3'-O-methyl epicatechin, we have compared its protective ef fects with that of epicatechin. The results provide the first evidence that 3'-O-methyl epicatechin inhibits cell death induced by hydrogen peroxide a nd that the mechanism involves suppression of caspase-3 activity as a marke r for apoptosis. Furthermore, the protection elicited by 3'-O-methyl epicat echin is not significantly different from that of epicatechin, suggesting t hat hydrogen-donating antioxidant activity is not the primary mechanism of protection.