Calixpyrroles: from Anion Ligands to Potential Anticancer Drugs

Since the discovery that calix[4]pyrrole can act as a ligand for anions and other species that can form multiple hydrogen bonds with its pyrrole NH units, this macrocyclic system, its derivatives, and related pyrrole-containing anion binders, have been a topic of an ever growing interest for their potential applications in diverse fields, including molecular recognition, sensing, catalysis, self-assembly, and the fabrication of smart materials. This review traces some contributions of the author to these topics, placing them in the context of the work developed by research groups worldwide without attempting to provide a comprehensive account of the field. As anions play a key role in the biological world, anion-binding receptors and calixpyrroles have emerged as potential drugs due to their ability to transport anions across membranes. Both antibacterial and cytotoxic effects against cancer cell lines have been reported for some chloride transporters. However, in the case of certain calixpyrrole derivatives, we gained evidence of their ability to cause genotoxic effects and hence to exhibit a cytotoxic action that does not appear correlated to anion transport. These observations might pave the way towards new anticancer drugs.