Synthesis of rhodamine B-benzenesulfonamide conjugates and their inhibitory activity against human α-and bacterial/fungal β-carbonic anhydrases

A series of fluorescent sulfonamide carbonic anhydrase (CA, EC 4.2.1.1) inhibitors were obtained by attaching rhodamine B moieties to the scaffold of benzenesulfonamides. The new compounds have been investigated for the inhibition of 12 human alpha-CA isoforms (hCA I-hCA XIV), three bacterial and one fungal beta-class enzymes from the pathogens Mycobacterium tuberculosis and Candida albicans. All types of inhibitory activities have been detected, with several compounds showing low nanomolar inhibition against the transmembrane isoforms hCA IX, XII (cancer-associated) and XIV. The beta-CAs were inhibited in the micromolar range by these compounds which may have applications for the imaging of hypoxic tumors or bacteria due to their fluorescent moieties. (C) 2011 Elsevier Ltd. All rights reserved.