Autoxidation of Model Membrane Systems: Cooxidation of Polyunsaturated Lecithins with Steroids, Fatty Acids, and α-Tocopherol

Article abstract of DOI:10.1021/ja00383a037

The autoxidation of diL-PC and 1S,2A-PC in aqueous emulsion with several cosubstrates was investigated.Cholesterol, 7-dehydrocholesterol, linolic acid, and α-tocopherol were cosubstrates in the autoxidation of dilinoleoylphosphatidylcholine (diLP-PC).The distribution of the products, tc and tt diene hydroperoxides, was determined and evaluated.It was concluded that cholesterol has a lower H atom donating ability (K_p) and 7-dehydrocholesterol a much higher K_p than diL-PC.Linoleic acid when mixed with diL-PC, diP-PC, or a mixture of the two was found to behave analogous to a mixture of just the two lecithins.The cooxidation of diL-PC with a α-tocopherol in the bilayer gave only trans,cis (tc) hydroperoxides, which can be ascribed to a very high k_inh for a α-tocopherol, a very efficient antioxidant. 1-Stearoyl-2-arachidonoylphosphatidilcholine (1S,2A-PC)bilayer autoxidation gave a product distribution very similar to arachidonic acid neat autoxidation.However the products from cooxidation of 1S,2A-PC bilayer with α-tocopherol unexpectedly did not include the 5-hydroperoxy eicosatetraenoic acid isomer (5-HPETE), although the 12, 15, 11, 9, and 8 isomers were present in almost equal amounts.