Factors that influence the deoxyribose oxidation assay for fenton reaction products

Abstract

The mechanism of oxidation of deoxyribose to thiobarbituric acid-reactive products by Fenton systems consisting of H 2O 2 and either Fe 2+ or Fe 2+ (EDTA) has been studied. With Fe 2+ (EDTA), dependences of product yield on reactant concentrations are consistent with a reaction involving OH: With Fe 2+ in 5–50 mM phosphate buffer, yields of oxidation products were much higher and increased with increasing deoxyribose concentration up to 30 mM. The product yield varied with H 2O 2 and Fe 2+ concentrations in a way to suggest competition between deoxyribose and both reactants. Deoxyribose oxidation by Fe 2+ and H 2O 2 was enhanced 1.5-fold by adding superoxide dismutase, even though superoxide generated by xanthine oxidase increased deoxyribose oxidation. These results are not as expected for a reaction involving free OH· or site localized OH· produced on the deoxyribose. They can be accommodated by a mechanism of deoxyribose oxidation involving an iroń(IV) species formed from H 2O 2 and Fe 2+, but the overall conclusion is that the system is too complex for definitive identification of the Fenton oxidant