title: Recycling and antioxidant activity of tocopherol homologs of differing hydrocarbon chain lengths in liver microsomes.
abstract: Tocopherols (vitamin E) function as inhibitors of lipid peroxidation in biomembranes by donating a hydrogen atom to the chain propagating lipid radicals, thus giving rise to chromanoxyl radicals of the antioxidant. We have shown that alpha-tocopherol homologs differing in the lengths of their hydrocarbon side chains (alpha-Cn) manifest strikingly different antioxidant potencies in membranes. The antioxidant activity of tocopherol homologs during (Fe2+ + ascorbate)- or (Fe2+ + NADPH)-induced lipid peroxidation in rat liver microsomes increased in the order alpha-tocopherol (alpha-C16) less than alpha-C11 less than alpha-C6 less than alpha-C1. Chromanoxyl radicals generated from alpha-tocopherol and its more polar homologs by an enzymatic oxidation system (lipoxygenase + linolenic acid) can be recycled in rat liver microsomes by NAD-PH-dependent electron transport or by ascorbate. The efficiency of recycling increased in the same order: alpha-tocopherol (alpha-C16) less than alpha-C11 less than alpha-C6 less than alpha-C1. Thus the high efficiency of regeneration of short-chain homologs of vitamin E may account for their high antioxidant potency.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley 94720.
authors.forename: V E
authors.initials: VE
authors.lastname: Kagan
authors.forename: E A
authors.initials: EA
authors.lastname: Serbinova
authors.forename: L
authors.initials: L
authors.lastname: Packer
mesh_terms: D000818:Animals; D000975:Antioxidants; D001205:Ascorbic Acid / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D015227:Lipid Peroxidation / Q000187:drug effects*; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D009249:NADP / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D005609:Free Radicals; D014810:Vitamin E; D009249:NADP; D001205:Ascorbic Acid