New spiroindoline-substituted sulphonamide compounds were synthesised and their inhibitory effects on the activity of purified human carbonic anhydrase I and II were evaluated. Human carbonic anhydrase isoenzymes (hCA-I and hCA-II) were purified from erythrocyte cells by affinity chromatography. The inhibitory effects of the 14 synthesised sulphonamides (6a-n) on esterase activities of these isoenzymes were studied in vitro. In relation to these activities, the inhibition equilibrium constants (Ki) were determined. The results showed that all the synthesised compounds inhibited the carbonic anhydrase (CA) isoenzyme activity. Among them, 6b was found to be the most active (Ki: 0.042 μM) for hCA I and 6a (Ki: 0.151 μM) for hCA II.
Keywords: Sulphonamide; carbonic anhydrase; enzyme inhibitor; spiroindoline.