ANTIOXIDATIVE ACTIVITIES OF FURANTHIOLS AND THIOPHENETHIOLS MEASURED IN LIPID-PEROXIDATION SYSTEMS AND BY TYROSYL RADICAL SCAVENGING ASSAY

Malonaldehyde formation from dilinolenoylphosphatidylcholine liposomes was inhibited by 2-methyl-3-furanthiol, 2-thiophenethiol, and furfuryl mercaptan. 2-Methyl-3-furanthiol and 2-thiophenethiol showed strong and comparable inhibitory activities, whereas furfuryl mercaptan showed only slight activity. 2-Methyl-3-furanthiol possessed synergistic activity with alpha-tocopherol in the lower concentrations. Both 2-methyl-3-furanthiol and 2-thiophenethiol scavenged tyrosyl radicals formed from L-tyrosine in aqueous solutions with activity similar to that of ascorbic acid, whereas furfuryl mercaptan and L-cysteine did not scavenge them. 2-Methyl-3-furanthiol reacted readily with H2O2 in aqueous buffer solutions, resulting in bis(2-methyl-3-furyl) disulfide. Scavenging of myoglobin tyrosyl radicals and the decomposition of H2O2 are proposed as plausible antioxidative mechanisms for 2-methyl-3-furanthiol and 2-thiophenethiol.