Strong dependence of the lipid peroxidation product spectrum whether Fe2+/O2 or Fe3+/O2 is used as oxidant1

Catalytic amounts of Fe²⁺ or Fe³⁺ ions are widely applied to induce simulated biological lipid peroxidation reactions. Independently, whether Fe²⁺ or Fe³⁺ were used, similar products were obtained. We show in this paper that the product spectrum is indeed very different, whether one ion species, either Fe²⁺ or Fe³⁺, is present in excess; thus, decomposition of (13S,9Z,11E) 13-hydroxyperoxy-9,11-octadecadienoic acid (13S-HPODE) generates in the presence of equimolar amounts of Fe²⁺ ions mainly the corresponding alcohol (13S,9Z,11E) 13-hydroxy-9,11-octadecadienoic acid besides 12,13-epoxy-11-hydroxy-9-octadecenoic acid (12,13-epHOD) and 13-oxo-9,11-octa-decadienoic acid (13-KODE), while decomposition of 13S-HPODE with equimolar amounts of Fe³⁺ produces mainly 12,13-epHOD, hydrolysis products thereof and other oxidized products, e.g., hydroxyoxo acids. In addition, unusually large amounts of aldehydes are formed, e.g., the amount of 4-hydroxy-nonenal was found to exceed that obtained by Fe²⁺ induced air oxidation for a factor of about 100. Since these further oxidation products are suspected to cause cell damage, liberated Fe³⁺ ions seem to be responsible for generation of toxic products in inflammatory diseases, e.g., atherosclerosis.