Abstract
The antioxidative and/or prooxidative activity of 4-methylcoumanrin (MC), 7-hydroxy-4-methylcoumarin (HMC) and 7,8-dihydroxy-4-methylcoumarin (DHMC), respectively, in the peroxidation of human low-density lipoprotein (LDL) has been studied. The peroxidation was initiated either thermally by water-soluble initiator 2,2′-azobis(2-amidinopropane hydrochloride) (AAPH), or photochemically by a triplet sensitizer benzophenone (BP) or its water-soluble analogue disodium 3,3′-disulfobenzophenonate (DSBP). The reaction kinetics were monitored by the uptake of oxygen and the depletion of α-tocopherol (TOH) present in the native LDL. Kinetic analysis of the peroxidation process demonstrated that DHMC is a good antioxidant for both the AAPH-initiated and BP- and DSBP-photosensitized peroxidation; HMC is a prooxidant for the AAPH-initiated and DSBP-photosensitized peroxidation, but an antioxidant for the BP-sensitized peroxidation; MC is a prooxidant in all of these initiation conditions. 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.
Published Version
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