title: Simultaneous determination of homologues of vitamin E and coenzyme Q and products of alpha-tocopherol oxidation.
abstract: A sensitive procedure is described for the simultaneous determination of vitamin E and coenzyme Q homologues and alpha-tocopherol oxidation products using two-isocratic step high pressure liquid chromatography (HPLC) and electrochemical detection in the oxidative mode. Zinc-catalyzed reduction in a post-column reactor allows the detection of alpha-tocopherolquinone, epoxy-tocopherolquinone, and ubiquinones. This technique was used to quantify lipophilic antioxidants in the liver tissue of rats treated or not with alpha-tocopherolquinone and in a plant oil. Alpha-tocopherolquinone and its epoxide derivatives, formed from alpha-tocopherol during iron-catalyzed phospholipid peroxidation, were also determined in a liposome suspension. The high selectivity and sensitivity of the coulometric detection system enabled use of low oxidation potentials giving little baseline noise, while a fast isolation procedure and quantitative recoveries of all oxidized and reduced forms made it possible to measure a high ubiquinol/ubiquinone ratio in liver tissue. Administration of alpha-tocopherolquinone to rats did not alter the antioxidant status of the liver, despite strong accumulation of both this quinone and its reduced form, alpha-tocopherolhydroquinone. These results indicate the presence of an efficient reductase and suggest that it could contribute to the protection of cellular membranes from oxidative stress.
authors.affiliation: INSERM U311, Etablissement de Transfusion Sanguine, Strasbourg, France.
authors.forename: C
authors.initials: C
authors.lastname: Leray
authors.forename: M D
authors.initials: MD
authors.lastname: Andriamampandry
authors.forename: M
authors.initials: M
authors.lastname: Freund
authors.forename: C
authors.initials: C
authors.lastname: Gachet
authors.forename: J P
authors.initials: JP
authors.lastname: Cazenave
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid / Q000379:methods* / Q000592:standards; D004355:Drug Stability; D007501:Iron / Q000737:chemistry; D015227:Lipid Peroxidation; D008081:Liposomes / Q000737:chemistry; D008099:Liver / Q000737:chemistry* / Q000187:drug effects; D008297:Male; D010938:Plant Oils; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D014451:Ubiquinone / Q000031:analogs & derivatives / Q000032:analysis*; D014810:Vitamin E / Q000031:analogs & derivatives / Q000032:analysis* / Q000737:chemistry* / Q000494:pharmacology; D015032:Zinc / Q000737:chemistry
chemical_list: D000975:Antioxidants; D008081:Liposomes; D010938:Plant Oils; D014451:Ubiquinone; D014810:Vitamin E; C002421:tocopherylquinone; D007501:Iron; D015032:Zinc; C003741:ubiquinol