Silver(I) complexes with antifungal drug econazole: structural characterization and antimicrobial activity study

Abstract

Two new silver(I) complexes with the antifungal agent econazole (ecz) of the general formula [Ag(еcz)2]X, X = CF3SO3− (Ag1) and PF6− (Ag2), were synthesized and structurally characterized by spectroscopic (1H NMR, IR and UV-Vis) and electrochemical methods. The crystal structure of Ag2 was determined by single crystal X-ray diffraction analysis, confirming an ideal linear geometry of the silver(I) ion in this complex. In addition, by utilising Hirshfeld surface analysis (HSA), it was verified that the crystal structure of Ag2 is stabilized by H⋯H, H⋯Cl, C⋯H, and H⋯F interactions. Density functional theory (DFT) calculations provided additional evidence for formation of the complexes in the solid state and their stability in solution. The coordination of ecz to the silver(I) ion endowed this agent with antibacterial activity against Gram-positive (Pseudomonas aeruginosa and Escherichia coli) and Gram-negative (Staphylococcus aureus and Listeria monocytogenes) bacteria. The most significant antibacterial activity of Ag1 and Ag2 was observed against S. aureus with 56- and 73-fold improvement, respectively, compared to the parent drug. Moreover, a study of the bacterial antibiofilm activity revealed that these complexes were able to prevent approximately 90% of biofilm formation at their low concentrations. Also, both complexes have shown more pronounced anti-Candida activity than econazole itself, being less toxic on the human normal fibroblast cell line MRC-5. The total amount of ergosterol was reduced in the presence of the subinhibitory concentrations of Ag1 and Ag2 complexes, which was also confirmed by a molecular docking study with two isomers of cytochrome P450 sterol 14α-demethylase, CYP51B and CYP130, as target receptors.