Oxidation of Unsaturated Fatty Acids by Ozone and Nitrogen Dioxide

Abstract

Trace quantities of ozone and nitrogen dioxide, 1.5 ppm, catalyzed the rapid oxidation of unsaturated fatty acids. Nitrogen dioxide-catalyzed oxidations were dependent upon the NO₂ concentration in the atmosphere. Both thin films and aqueous emulsions of fatty acids are oxidized by NO₂ through a mechanism akin to the spontaneous autoxidation in air. Phenolic antioxidants, including vitamin E, retarded the oxidation. Ozone catalyzed a more rapid and complete oxidation than NO₂ by a direct attack upon the double bonds of the fatty acid. Phenolic antioxidants are protective only in aqueous emulsions where the oxidation proceeds by peroxidation as well. Oxidation of essential tissue polyunsaturated fatty acids by O₃ and NO₂ is a likely common mechanism of toxicity.