Polyunsaturated fatty acid alkoxyl radicals exist as carbon-centered epoxyallylic radicals: A key step in hydroperoxide-amplified lipid peroxidation

• Published in: Chemical research in toxicology 1993-07, Vol.6 (4), p.413-416
• Main Authors: Wilcox, Allan L, Marnett, Lawrence J
• Format: Article
• Language: English
• Subjects: Antioxidants; Biological and medical sciences; Cell metabolism, cell oxidation; Cell physiology; Chromatography, High Pressure Liquid; Cyclization; Fatty Acids, Unsaturated - chemistry; Free Radicals; Fundamental and applied biological sciences. Psychology; Hydrogen Peroxide; Iron Chelating Agents; Linolenic Acids; Lipid Peroxidation; Lipid Peroxides; Molecular and cellular biology; Phenols - chemistry; Porphyrins - chemistry
• ISSN: 0893-228X; 1520-5010
• DOI: 10.1021/tx00034a003

13-Hydroperoxyoctadeca-9,11,15-trienoic acid was reacted with a catalytic amount of 5,10,15,20-tetraphenyl-21H,23H-porphyrin iron(III) chloride in dichloromethane containing 2,4,6-tri-tert-butylphenol. The principal products were identified as 13-oxooctadeca-9,11,15-trienoic acid, 13-oxotrideca-9,11-dienoic acid, and a series of isomeric epoxyaryl ethers [9-(2,4,6-tri-tert-butylphenoxy)-12,13-epoxyoctadec-10-enoic acids and 11-(2,4,6-tri-tert-butylphenoxy)-12,13-epoxyoctadec-9-enoic acids]. The epoxyaryl ethers are coupling products of 2,4,6-tri-tert-butylphenoxyl radical and an epoxyallylic radical formed by cyclization of an intermediate alkoxyl radical. The high yield of epoxyaryl ethers relative to 13-oxotrideca-9,11-dienoic acid suggests the equilibrium between alkoxyl radical and epoxyallylic radical lies predominantly toward epoxyallylic radical. This cyclization appears to be a key step in the amplification of lipid peroxidation by polyunsaturated fatty acid hydroperoxides.