A study of the reactivity of HO2/O2- with unsaturated fatty acids

The reaction of perhydroxyl radical (HO2) with linoleic, linolenic, and arachidonic acids has been studied in aqueous ethanolic solutions by the stopped flow technique. The corresponding rate constants are 1.2 x 10(3), 1.7 x 10(3), and 3.0 x 10(3) M-1 S-1, respectively. While kinetic results suggest that the HO2 radical reacts with the double allylic H atom of the polyunsaturated fatty acids, thermodynamic approximations indicate that the reaction is exothermic by approximately 10 kcal/mol. The relevance of this reaction to membrane damage observed in biological systems that have been exposed to HO2/O2- radicals is discussed.