ANGIOTENSIN-CONVERTING ENZYME-INHIBITORS AS OXYGEN-FREE RADICAL SCAVENGERS

The authors have compared the ability of two non-SH-containing angiote nsin converting enzyme (ACE) inhibitors (enalaprilat and lisinopril) w ith an -SH containing ACE inhibitor (captopril) to scavenge the hydrox yl radical (.OH). All three compounds were able to scavenge .OH radica ls generated in free solution at approximately diffusion-controled rat es (10(10) M-1 s-1) as established by the deoxyribose assay in the pre sence of EDTA. The compounds also inhibited deoxyribose degradation in reaction mixtures which did not contain EDTA but not so effectively. This later finding also suggests that they have some degree of metal-b inding capability. Chemiluminescence assays of oxidation of hypoxanthi ne by xanthine oxidase in the presence of luminol, confirm that the th ree ACE inhibitors are oxygen free radical scavengers. Our results ind icate that the presence of a sulphydryl group in the chemical structur e of ACE inhibitors is not relevant for their oxygen free radical scav enging ability.