Two novel silver(I) complexes of the biologically active ligand miconazole in the form of Ag(MCZ)2X (MCZ = 1-[2-(2,4-dichlorobenzyloxy)-2-(2,4-dichlorophenyl)ethyl]-1H-imidazole]; X = NO3− (1), ClO4− (2)) were synthesized and fully characterized. The complexes were obtained by reactions of Ag(I) salts with miconazole (MCZ). Silver(I) complexes were characterized by elemental analysis, 1H-NMR and infrared (IR) spectroscopy, electrospray ionization (ESI)-MS spectrometry, and X-ray-crystallography. This work also presents a cytotoxicity study of the silver(I) complexes of miconazole and appropriate silver(I) salts using Balb/c 3T3 and HepG2 cell lines. The cytotoxicity of the compounds was assessed based on four biochemical endpoints: lysosomal activity (neutral red uptake (NRU) assay), mitochondrial activity (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay), total protein content (TPC assay), and cellular membrane integrity (lactate dehydrogenase (LDH) assay). The cancer HepG2 cells were more sensitive to the complexes tested, and the most affected endpoint was cellular membrane damage compared to Balb/c 3T3 fibroblasts. Moreover, study complexes inhibited the growth of cancer cells at submicromolecular concentrations (0.26–0.47 μM) lower than that required for the anticancer agent, cisplatin, in MTT, NRU, and TPC assays. Both complexes were characterized by higher toxicity to human cancer cells (HepG2) than silver(I) salts and the free ligand. Combination of Ag(I) salts with miconazole is associated with the marked improvement of cytotoxic activities that can be considered as the significant point in the construction of a new generation of antineoplastic agents.

In a previous article, we reported on the higher toxicity of silver(I) complexes of miconazole [Ag(MCZ)2NO3 (1)] and [Ag(MCZ)2ClO4 (2)] in HepG2 tumor cells compared to the corresponding salts of silver, miconazole and cisplatin. Here, we present the synthesis of two silver(I) complexes of miconazole containing two new counter ions in the form of Ag(MCZ)2X (MCZ = 1-[2-(2,4-dichlorobenzyloxy)-2-(2,4-dichlorophenyl)ethyl]-1H-imidazole]; X = BF4− (3), SbF6− (4)). The novel silver(I) complexes were characterized by elemental analysis, 1H NMR, 13C NMR and infrared (IR) spectroscopy, electrospray ionization (ESI)-MS spectrometry and X-ray-crystallography. In the present study, the antimicrobial activity of all obtained silver(I) complexes of miconazole against six strains of Gram-positive bacteria, five strains of Gram-negative bacteria and yeasts was evaluated. The results were compared with those of a silver sulfadiazine drug, the corresponding silver salts and the free ligand. Silver(I) complexes exhibited significant activity against Gram-positive bacteria, which was much better than that of silver sulfadiazine and silver salts. The highest antimicrobial activity was observed for the complex containing the nitrate counter ion. All Ag(I) complexes of miconazole resulted in much better inhibition of yeast growth than silver sulfadiazine, silver salts and miconazole. Moreover, the synthesized silver(I) complexes showed good or moderate activity against Gram-negative bacteria compared to the free ligand.