Oxidation of alpha-tocopherol during the peroxidation of dilinoleoylphosphatidylcholine in liposomes.
Liposomal suspensions of dilinoleoylphosphatidylcholine (DLPC) containing alpha-tocopherol (0.1 mol%, based on DLPC were oxidized at 37 degrees C. The oxidation was initiated by a lipid-soluble or water-soluble free radical initiator, or by the addition of CuSO4 and fructose. In all the oxidation systems, alpha-tocopherol suppressed the formation of DLPC hydroperoxides until all the alpha-tocopherol had been depleted. The oxidation products of alpha-tocopherol were 8a-alkyldioxy-alpha-tocopherones, 5,6-epoxy-alpha-tocopherylquinone, 2,3-epoxy-alpha-tocopherylquinone, and alpha-tocopherylquinone. The 8a-alkyldioxy-alpha-tocopherones were decomposed in the liposomes primarily by being hydrolyzed to produce alpha-tocopherylquinone. The results indicate that alpha-tocopherol can trap peroxyl radical to form 8a-alkyldioxy-alpha-tocopherones which are hydrolyzed to alpha-tocopherylquinone in phospholipid bilayers. In another oxidation pathway, alpha-tocopherol may be oxidized by peroxyl radicals to form isomeric epoxy-alpha-tocopherylquinones.
Yamauchi
R
R
Department of Food Science, Faculty of Agriculture, Gifu University, Japan.
Yagi
Y
Y
Kato
K
K
D000578:Amidines; D001391:Azo Compounds; D003300:Copper / Q000494:pharmacology; D019327:Copper Sulfate; D005609:Free Radicals; D005632:Fructose / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000502:physiology*; D008081:Liposomes; D009570:Nitriles; D010084:Oxidation-Reduction; D010713:Phosphatidylcholines / Q000378:metabolism*; D012995:Solubility; D014810:Vitamin E / Q000494:pharmacology*
D000578:Amidines; D001391:Azo Compounds; D005609:Free Radicals; D008081:Liposomes; D009570:Nitriles; D010713:Phosphatidylcholines; C055792:2,2'-azobis(2,4-dimethylvaleronitrile); D014810:Vitamin E; D005632:Fructose; C002448:1,2-linoleoylphosphatidylcholine; C046728:2,2'-azobis(2-amidinopropane); D003300:Copper; D019327:Copper Sulfate