Antioxidant effect of dipicolinic acid on the metal-catalyzed lipid peroxidation and enzyme inactivation

Antioxidant action of pyridine compounds was analyzed in relation to the ir on coordination. Iron-mediated lipid peroxidation, determined as the format ion of thiobarbituric acid-reactive substances, was inhibited by dipicolini c acid (pyridine 2,6-dicarboxylic acid), but not by other pyridine dicarbox ylates including quinolinic acid, lutidinic acid, cinchomeronic acid, isoci nchomeronic acid. Dipicolinic acid further inhibited metal-catalyzed oxidat ion of protein, evaluated as the hydroxyl radical-mediated inactivation of AMP deaminase under the in situ conditions of yeast; however, other pyridin e dicarboxylates did not show any protective effect. Dipicolinic acid enhan ced the autooxidation of Fe2+ ion, whereas other pyridine carboxylates rath er inhibited the autooxidation of ferrous ion. Antioxidant effect of dipico linic acid can be explained by enhancement of the oxidation of ferrous ion as a prooxidant: this may be due to the electron-deficient nature of pyridi ne ring with dicarboxylic acid at ortho position.