Antioxidant activity of indapamide and its metabolite.

An antioxidant activity of indapamide (IDP) and its metabolite (OH-IDP) is demonstrated in this study. Both IDP and OH-IDP were found to scavenge 1,1-diphenyl-2-picryl-hydrazyl free radical. The scavenging effect of OH-IDP was stronger than that of IDP. Lipid peroxidation of rat liver microsomes initiated by reduced nicotinamide adenine dinucleotide phosphate (NADPH) and adenosine diphosphate (ADP)-Fe3+ was inhibited by IDP and OH-IDP with IC50 values of about 6 and 2 microM, respectively. The lipid peroxidation in human erythrocyte membrane, induced by 2,2'-azobis-(2-amidinopropane dihydrochloride) treatment, was also inhibited by 10 microM IDP. The antioxidant capacity of OH-IDP was at almost the same level as that of alpha-tocopherol, tested for comparison. The present data show that IDP and OH-IDP at micromolar concentrations are able to trap the free radicals involved in the lipid peroxidation.