HYDROXYL RADICAL SCAVENGING ACTIVITY OF SALICYLIC-ACID AND ITS HYDROXYLATED METABOLITES - AN ESR STUDY

The hydroxyl radical scavenging activity of salicylic acid, 2,5 (3,4 and 2,3)-dihydroxybenzoic acids and catechol was investigated. To quantify their antioxidative effects, a test system based on the inhibition of the ESR signal of 5,5-dimethyl-2-hydroxypyrrolidine-N-oxide (DMPO-OH) (obtained by addition of hydroxyl radical (generated by Fenton reaction) with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO)) by the tested compounds was applied. It was found that catechol was 6600 times more potent than salicylic acid, 2,5 or 2,3-dihydroxylbenzoic acids. This effect is discussed in terms of unfavourable ortho interactions between the phenolic and carboxylic acid functions.