Antioxidant effect of coumarin derivatives on free radical initiated and photosensitized peroxidation of linoleic acid in micelles

Abstract

The antioxidant activity of 4-methylcoumarin (MC), 6-hydroxy-4-methylcoumarin (HMC) and 7,8-dihydroxy-4-methylcoumarin (DHMC), respectively, in the inhibition of peroxidation of linoleic acid in micellar systems has been studied. The peroxidation was initiated either thermally by water-soluble initiator 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AMPAD) or photochemically by a triplet sensitizer benzophenone (BP) in the anionic micelle sodium dodecyl sulfate (SDS) or in the cationic micelle cetyl trimethylammonium bromide (CTAB). It was found that DHMC is a good antioxidant for both AMPAD-initiated and BP-sensitized peroxidation in both SDS and CTAB micelles, while HMC is only active for BP-sensitized peroxidation in SDS micelles. MC is ineffective in any case. The antioxidative action of the coumarin derivatives may include trapping the initiating radicals, trapping the propagating lipid peroxyl radicals, recycling α-tocopherol and/or deactivating the excited photosensitizer.