Carbonic Anhydrase Inhibitors: Inhibition of Human Erythrocyte Isozymes I and II with a Series of Phenolic Acids

The inhibitory effects of some phenolic acids on the cytosolic human carbonic anhydrase (hCA, EC 4.2.1.1) isozymes hCA I and hCA II were investigated. Ellagic acid, gallic acid, ferulic acid, caffeic acid, quercetin, p-coumaric acid, p-hydroxybenzoic acid, and syringic acid showed KI values in the range of 99-1061 mu M for hCA I and of 105-758 mu M against hCA II, respectively. Quercetin (for hCA I), p-coumaric acid (for hCA II), and gallic acid (for hCA II) exhibited competitive inhibitory effects with 4-nitrophenyl acetate as substrate. All of the other phenolic acids were found as non-competitive inhibitors with 4-nitrophenylacetate as substrate for hCA I and hCA II. The phenolic acids investigated here showed thus interesting hCA I and hCA II inhibitory effects and might be used as leads for generating enzyme inhibitors possibly targeting other CA isoforms which have not been yet assayed for their interactions with such agents.