INFLUENCE OF THIOL-REGULATED REDOX SYSTEM ON THE ANTIOXIDANT POTENTIALS OF POLYPHENOLIC AND SELENIUM COMPOUNDS

Abstract

It is established that the precise underlying antioxidant mechanism of polyphenols (quercetin and tannic acid) is based on the ability to either chelate transition metals, scavenge radicals or reduce transition elements, while the antioxidant mechanism of diphenyldiselenide is centered solely on their glutathione peroxidase mimicry which involves thiols oxidation. However, it is not clear if the polyphenols can also modulate thiol dynamics as a component of their antioxidant action. Hence in this study, the influence of the thiol alkylating agent, iodoacetamide (2mM) on the antioxidant action of quercetin, tannic acid and diphenyldiselenide was tested. In addition, the possible involvement of the thiols of cerebral sodium pump and delta aminolevulinic acid dehydratase in the antioxidant action of the polyphenols and selenium compounds were also evaluated. The results indicated the ability of both polyphenols (tannic acid and quercetin) and diphenyldiselenide to prevent lipid peroxidation were diminished in the presence of the thiol modifier (iodoacetamide), thus indicating that the antioxidant mechanism of the polyphenol is dependent on thiol oxidation in tissue homogenates. In addition, both polyphenols and the diphenyldiselenide inhibited the activities of the sulphydryl proteins cerebral sodium pump and delta aminolevulinic acid dehydratase, suggesting that the thiols of these enzymes may be critical to the antioxidant action of the polyphenols and diphenyldiselenide. Apparently, it appears that different classes of the antioxidant compounds may have a central mechanism that is critically related to thiol modulation.