Evaluation of hydroxyl radical-scavenging property of purpurogallin using high pressure liquid chromatography

Purpurogallin (PPG) has been used as an additive to edible and non-edible oils or fats to retard oxidation. Its antioxidant mechanism is not known. We investigated the ability of PPG to scavenge exogenously generated hydroxyl radicals (.OH) using a sensitive high pressure liquid chromatographic (HPLC) method. .OH was generated by photolysis of H2O2 (1.25-10 mumoles) with UV light and was trapped with salicylic acid (500 nmoles). Salicylic acid is hydroxylated to produce .OH adduct products 2,3- and 2,5-dihydroxybenzoic acid (DHBA). H2O2 produced concentration-dependent .OH as estimated by generation of 2,3- and 2,5-DHBA. PPG (100, 200, 300, 400, 500, and 600 nmoles) produced concentration-dependent decreases in .OH adduct products (approximately 70% inhibition with 600 nmoles of PPG). It did not affect the peak of standard 2,3- and 2,5-DHBA indicating that the decrease in the adduct product generated by H2O2 is due to scavenging of .OH. These results indicate that photolysis of H2O2 by UV light produces .OH and that PPG scavenges .OH.