THE SHORT-CHAIN HOMOLOG OF DIHYDROLIPOIC ACID, TETRANORDIHYDROLIPOATE, PROTECTS AGAINST IRON-INDUCED LIPID-PEROXIDATION IN THE AQUEOUS-PHASE

Because iron is involved in catalysis of many biological oxidations, it is important to investigate new and novel antioxidants in terms of their effect on iron-catalyzed oxidations. We investigated the effect of dihydrolipoic acid (6,8-dimercaptooctanoic acid (DHLA)), its homologues (4,6-dimercaptohexanoic acid (bisnorDHLA) and 2,4-dimecraptobutanoic acid (tetranorDHLA)) and methyl 6,8-dimercaptooctanoate (methylDHLA) on Fe(II))-citrate-catalyzed lipid peroxide-dependent lipid peroxidation in lipid-dispersed and liposome systems. In the lipid-dispersed system, tetranorDHLA inhibited conjugated diene formation induced by Fe(II)-citrate. In the presence of tetranorDHLA, oxygen was consumed more rapidly in the reaction mixture than in the presence of the other compounds, but the oxidation rate of Fe(II))-citrate in the reaction mixture was slower than in the presence of the other compounds. This suggests that tetranorDHLA inhibited lipid peroxidation by the oxidation of tetranorDHLA itself at the site where the lipid was oxidized. (C) 1994 Academic Press, Inc.