title: Oxidative catabolism of alpha-tocopherol in rat liver microsomes.
abstract: The goal of this study was to clarify the mechanism responsible for the catabolism of alpha-tocopherol. The vitamin, bound to albumin, was incubated with rat liver microsomes and appeared to be broken down. Optimal production of the metabolite was obtained when 1 mg of microsomal protein was incubated with 36 microM of alpha-tocopherol in the presence of 1.5 mM of NADPH. Chromatographic and mass spectrometric analyses of the metabolite led to the conclusion that it consists of an omega-acid with an opened chroman ring, although we could not perform nuclear magnetic resonance analysis to confirm this. Our data show that alpha-tocopherol is omega-oxidized to a carboxylic acid and that this process can occur in rat liver microsomes in the presence of NADPH and O2. The oxidation to the quinone structure appears to be a subsequent event that may be artifactual and/or catalyzed by a microsomal enzyme(s).
authors.affiliation: Department of Clinical Chemistry, Katholieke Universiteit Leuven, Belgium.
authors.forename: H
authors.initials: H
authors.lastname: Van Houte
authors.forename: E
authors.initials: E
authors.lastname: De Hoffmann
authors.forename: P P
authors.initials: PP
authors.lastname: Van Veldhoven
authors.forename: G P
authors.initials: GP
authors.lastname: Mannaerts
authors.forename: H
authors.initials: H
authors.lastname: Carchon
authors.forename: M I
authors.initials: MI
authors.lastname: Baes
authors.forename: P E
authors.initials: PE
authors.lastname: Declercq
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D009249:NADP / Q000494:pharmacology; D010084:Oxidation-Reduction; D010100:Oxygen / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D024502:alpha-Tocopherol / Q000378:metabolism*
chemical_list: D009249:NADP; D024502:alpha-Tocopherol; D010100:Oxygen