Peroxidation of polyunsaturated fatty acids, initiated by the direct interaction between a cobalt porphyrin complex and polyunsaturated fatty acids

Abstract

It has been shown that a cobalt porphyrin, CoTPPCl (TPP = tetraphenylporphyrin), can initiate the autoxidative radical-chain peroxidation of polyunsaturated fatty acids and esters (LH: linoleic acid, methyl linoleate, and linolenic acid) in an oxygen-saturated MeCN solution at 333 K by the direct interaction between CoTPPCl and LH, i.e., the one-electron reduction of CoTPPCI by LH, based on independent kinetic studies on the initiation step in deaerated MeCN and the overall CoTPP⁺-catalysed peroxidation of LH by dioxygen. The CoTPP⁺ complex can function not only as an initiator but also a catalyst, as demonstrated by independent kinetic studies on the catalyst regeneration step, the oxidation of CoTPP by dioxygen in the presence of LH. In addition, the cobalt(II) porphyrin complex, CoTPP, acts as a radical scavenger by the one-electron reduction of the chain carrier radicals, lipid peroxyl radicals.