The effects of α-tocopherol on site-specific lipid peroxidation induced by iron in charged micelles

α-Tocopherol inhibited H₂O₂-Fe²⁺-induced lipid peroxidation of linoleic acid (LA) by scavenging OH radicals in tetradecyltrimethylammonium bromide (TTAB) micelles. The inhibiting ability of α-tocopherol was much greater than that of OH-radical scavengers mannitol and t-butanol. In contrast, α-tocopherol enhanced linoleic acid hydroperoxide (LOOH)Fe²⁺-induced lipid peroxidation through regeneration of Fe²⁺ in sodium dodecyl sulfate (SDS) micelles containing LA. α-Tocopherol was oxidized by Fenton's reagent (FeSO₄ + H₂O₂) at a higher rate in SDS micelles than in TTAB micelles. The likely oxidants were OH radicals in the former and Fe³⁺ in the latter. Both reagents formed in the Fenton reaction. Ferrous ion catalyzed in a dose-dependent manner the decomposition of LOOH and conjugated diene compounds in SDS but not in TTAB micelles. α-Tocopherol and Fe³⁺ individually had no effect on the decomposition of LOOH, but together were quite effective. The rate of the decomposition was a function of the concentration of α-tocopherol. The mechanism of "site-specific" antioxidant action of α-tocopherol in charged micelles is discussed.