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 prepared by attaching rhodamine B moieties to the scaffold of benzenesulfonamides. ► The compounds have been investigated for the inhibition of 12 human α-CA isoforms (hCA I-hCA XIV), three bacterial and one fungal β-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 β-CAs were inhibited in the micromolar range by these compounds. ► Fluorescent sulfonamide CA inhibitors may have applications for the imaging of hypoxic tumors or of bacteria.