Antibacterial and Antiparasitic Activity of Manganese(I) Tricarbonyl Complexes with Ketoconazole, Miconazole, and Clotrimazole Ligands

Five manganese­(I) tricarbonyl complexes of the general formula [Mn­(CO)₃(bpy^R,R)­(azole)]­PF₆ with R = H, COOCH₃, and azole = ketoconazole (ktz), miconazole (mcz), and clotrimazole (ctz) were synthesized and fully charaterized, including X-ray structure analysis for the ctz compound. The antibacterial activity on a panel of eight Gram-positive and Gram-negative bacterial strains was determined. While there was no effect on the latter microorganisms, the ctz complex showed submicromolar activity on Staphylococcus aureus and S. epidermidis with MIC values of 0.625 μM. Antiparasitic activity was investigated on Leishmania major and Trypanosoma brucei. Coordination of the organic azole drugs to the Mn­(CO)₃ moiety led to complexes with low micromolar IC₅₀ values, but their potential for antileishmanial therapy is low due to comparable toxicity on mammalian cell lines 293T and J774.1. In contrast, the antitrypanosomal activity is much more promising, and the most potent compound incorparting the ktz ligand has an IC₅₀ value on T. brucei of 0.7 μM with selectivity on parasitic over mammalian cells as expressed by a selectivity index above 10. These results demonstrate that metal coordination of established drugs can significantly improve their biological activity and expand their range of medicinal applications.