Preparation and characterization of 8a-(phosphatidylcholine-dioxy)-alpha-tocopherones and their formation during the peroxidation of phosphatidylcholine in liposomes.
alpha-Tocopherol was reacted with the phosphatidylcholines (PCs), 1-palmitoyl-2-linoleoyl-3-sn-PC (PLPC), 1-palmitoyl-2-linolenoyl-3-sn-PC, 1-palmitoyl-2-arachidonoyl-3-sn-PC (PAPC) and 1-stearoyl-2-arachidonoyl-3-sn-PC, in the presence of the free radical initiator, 2,2'-azobis (2,4-dimethylvaleronitrile), at 37 degrees C. The addition products of alpha-tocopherol with the PC peroxyl radicals were isolated and identified as 8a-(PC-dioxy)-alpha-tocopherones, in which the peroxyl radicals derived from each PC molecule attacked the 8a-position of the alpha-tocopheroxyl radical. The antioxidative efficiency of alpha-tocopherol against the peroxidation of PLPC and PAPC in liposomes was assessed by the formation of the reaction products of alpha-tocopherol. When alpha-tocopherol was oxidized in the presence of the water-soluble free radical initiator, 2,2'-azobis (2-amidinopropane) dihydrochloride, epoxy-alpha-tocopherylquinones were mainly produced together with 8a-(PC-dioxy)-alpha-tocopherones and alpha-tocopherylquinone. The yield of alpha-tocopherylquinone was increased by treating each sample with dilute acid which indicates the presence of tocopherone precursors other than the 8a-(PC-dioxy)-alpha-tocopherones. The same products were also detected from iron-dependent peroxidation, although the yields were very low.
Yamauchi
R
R
Department of Food Science, Faculty of Agriculture, Gifu University, Japan. yamautir@cc.gifu-u.ac.jp
Mizuno
H
H
Kato
K
K
D000578:Amidines / Q000737:chemistry; D005609:Free Radicals; D015227:Lipid Peroxidation / Q000187:drug effects; D008081:Liposomes / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry; D010713:Phosphatidylcholines / Q000737:chemistry*; D010742:Phospholipid Ethers / Q000737:chemistry; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology
D000578:Amidines; D005609:Free Radicals; D008081:Liposomes; D016877:Oxidants; D010713:Phosphatidylcholines; D010742:Phospholipid Ethers; D014810:Vitamin E; C043051:1-O-hexadecyl-2-arachidonyl-sn-glycero-3-phosphocholine; C055402:1-palmitoyl-2-linoleoylphosphatidylcholine; C046728:2,2'-azobis(2-amidinopropane); C002421:tocopherylquinone