Quantitative Effects of Iron Chelators on Hydroxyl Radical Production by the Superoxide-Driven Fenton Reaction

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Abstract
Iron bound to certain chelators is known to promote the conversion of superoxide radicals (O−2;) to hydroxyl radicals (HO−) by the superoxide-driven Fenton reaction. The production of HO− by various iron chelates was studied using the reaction of dimethyl sulfoxide and HO− to produce methane sulphinic acid. Methane sulphinic acid was quantified by use of a simple colorimetric assay and used to determine the amounts of HO− produced. Superoxide was generated from 200 μ M hypoxanthine and 0.05 U/ml xanthine oxidase in the presence of 0–100 μM iron and 100μM of each chelator. The results of this preliminary investigation illustrate that, at physiological pH, the superoxide-driven Fenton reaction is significantly promoted by iron chelated to EDTA. nitrilotriacetate, and citrate, but is not promoted by the other anions studied.