INHIBITORY EFFECTS OF CHLOROGENIC ACIDS ON LINOLEIC-ACID PEROXIDATIONAND HEMOLYSIS

Antioxidant activities of chlorogenic acid and related catechols were investigated by both the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging system and the superoxide anion-mediated linoleic acid pero xidation system. At 10 mu M, chlorogenic acid, 3,5-dicaffeoylquinic ac id, caffeic acid and protocatechuic acid showed more scavenging activi ties on DPPH than dl-alpha-tocopherol or ascorbic acid. DPPH radical s cavenging activities of these compounds increased dose-dependently at concentrations ranging from 1 to 50 mu M; 1 mol of chlorogenic acid re acted with ca 4 mol of radical, and 1 mol of 3,5-dicaffeoylquinic acid with ca 6 mol of radical. Chlorogenic acid, 3,5-dicaffeoylquinic acid and caffeic acid inhibited the formation of conjugated diene from lin oleic acid. The inhibitory activity of 3,5-dicaffeoylquinic acid was s tronger than that of chlorogenic acid or caffeic acid; dl-a-tocopherol was the most inhibitory of the other catechols tested. Effects on the haemolysis and peroxidation of mouse erythrocytes induced by H2O2 was also examined. Caffeic acid, chlorogenic acid, 3,5-dicaffeoylquinic a cid and dl-alpha-tocopherol exhibited strong inhibitory activites, but cinnamic acid, p-coumaric acid, ferulic acid, protocatechuic acid and vanillic acid were ineffective. Caffeic acid (25 mu) inhibited the ru pture and haemolysis of erythrocytes.