title: Analysis of vitamin E and its oxidation products by HPLC with electrochemical detection.
abstract: A sensitive HPLC procedure with postcolumn reduction and electrochemical detection was developed for the analysis of vitamin E and its oxidation products, alpha-tocopherylquinone, epoxy-alpha-tocopherylquinones, and 8a-(lipid-dioxy)-alpha-tocopherones. After the separation on a reversed-phase column, on-line zinc-catalyzed reduction allowed the detection of alpha-tocopherylquinone and epoxy-alpha-tocopheryl-quinones, whereas platinum-catalyzed reduction allowed the detection of 8a-(lipid-dioxy)-alpha-tocopherones. The lowest detectable level of each compound was about 0.2 pmol at the signal-to-noise ratio of 3. This method was applied to the detection of alpha-tocopherol products in peroxidized human plasma. When the plasma was peroxidized by the addition of a free radical initiator, peaks corresponding to alpha-tocopherylquinone, epoxy-alpha-tocopherylquinones, and the addition products of alpha-tocopherol with peroxyl radicals derived from cholesteryl ester hydroperoxides and PC hydroperoxides were observed. The amount of these oxidation products in the plasma increased with the depletion of endogenous alpha-tocopherol. The results indicate that the method is useful to detect the oxidation products formed by the peroxyl radical-trapping reactions of alpha-tocopherol in biological systems.
authors.affiliation: Department of Bioprocessing, Faculty of Agriculture, Gifu University, Gifu City, Japan. yamautir@cc.gifu-u.ac.jp
authors.forename: Ryo
authors.initials: R
authors.lastname: Yamauchi
authors.forename: Hiroki
authors.initials: H
authors.lastname: Noro
authors.forename: Makoto
authors.initials: M
authors.lastname: Shimoyamada
authors.forename: Koji
authors.initials: K
authors.lastname: Kato
mesh_terms: D000328:Adult; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004563:Electrochemistry / Q000379:methods*; D006801:Humans; D008297:Male; D015394:Molecular Structure; D010084:Oxidation-Reduction; D012680:Sensitivity and Specificity; D014810:Vitamin E / Q000032:analysis* / Q000097:blood / Q000378:metabolism*
chemical_list: D014810:Vitamin E