Quantitative effects of iron chelators on hydroxyl radical production by the superoxide-driven fenton reaction.

Iron bound to certain chelators is known to promote the conversion of superoxide radicals (O2-) 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 microM hypoxanthine and 0.05 U/ml xanthine oxidase in the presence of 0-100 microM iron and 100 microM 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.