Superoxide dismutase activity of the captopril-iron complex.

With an assay that generates superoxide anion radicals without the intervention of metal ions we investigated the antioxidant properties of captopril, an angiotensin-converting enzyme inhibitor with a sulfhydryl group. Under these conditions, increasing concentrations of the drug were seen not to scavenge O.-2 directly. However, a combination of captopril and iron could bring about the breakdown of the superoxide anion; a result that may help to understand the free radical-scavenging properties of captopril.