Discovery of new azoles with potent activity against Candida spp. and Candida albicans biofilms through virtual screening

Abstract

Systemic candidiasis is a rampant bloodstream infection of Candida spp. and C. albicans is the major pathogen isolated from infected humans. Azoles, the most common class of antifungals which suffer from increasing resistance, and especially intrinsically resistant non-albicans Candida (NAC) species, act by inhibiting fungal lanosterol 14α-demethylase (CYP51). In this study we identified a number of azole compounds in 1-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl)ethanol/ethanone oxime ester structure through virtual screening using consensus scoring approach, synthesized and tested them for their antifungal properties. We reached several hits with potent activity against azole-susceptible and azole-resistant Candida spp. as well as biofilms of C. albicans. 5i's minimum inhibitor concentration (MIC) was 0.125 μg/ml against C. albicans, 0.5 μg/ml against C. krusei and 1 μg/ml against azole-resistant C. tropicalis isolate. Considering the MIC values of fluconazole against these fungi (0.5, 32 and 512 μg/ml, respectively), 5i emerged as a highly potent derivative. The minimum biofilm inhibitor concentration (MBIC) of 5c, 5j, and 5p were 0.5 μg/ml (and 5i was 2 μg/ml) against C. albicans biofilms, lower than that of amphotericin B (4 μg/ml), a first-line antifungal with antibiofilm activity. In addition, the active compounds showed neglectable toxicity to human monocytic cell line. We further analyzed the docking poses of the active compounds in C. albicans CYP51 (CACYP51) homology model catalytic site and identified molecular interactions in agreement with those of known azoles with fungal CYP51s and mutagenesis studies of CACYP51. We observed the stability of CACYP51 in complex with 5i in molecular dynamics simulations.

Keywords: Azoles; Biofilm; Candida albicans; Consensus scoring; Cytotoxicity; Molecular docking; Molecular dynamics simulations.