Oxidative catabolism of alpha-tocopherol in rat liver microsomes.
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).
Van Houte
H
H
Department of Clinical Chemistry, Katholieke Universiteit Leuven, Belgium.
De Hoffmann
E
E
Van Veldhoven
P P
PP
Mannaerts
G P
GP
Carchon
H
H
Baes
M I
MI
Declercq
P E
PE
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*
D009249:NADP; D024502:alpha-Tocopherol; D010100:Oxygen