Design and mechanistic evaluation of chalcone–quinoline–triazole hybrids as antifungal CYP51 inhibitors

Abstract

A series of novel chalcone–quinoline–triazole hybrid compounds were rationally designed, synthesised, and evaluated for antifungal activity against clinically relevant Candida species, including C. albicans, C. glabrata, and C. krusei. Among the synthesized derivatives, compound 7b exhibited the most potent antifungal activity, with minimum inhibitory concentration (MIC) values ranging from 6.25 to 12.5 µM, surpassing the reference antifungal ketoconazole under identical experimental conditions. Time–kill kinetic studies further confirmed its concentration- and time-dependent fungicidal activity. Mechanistic investigations demonstrated that compound 7b markedly disrupted fungal sterol biosynthesis, as evidenced by significant ergosterol depletion, lanosterol accumulation, and a pronounced reduction in the ergosterol/lanosterol ratio across all tested Candida species. Concentration–response analysis of the normalised ergosterol/lanosterol ratio yielded low apparent IC₅₀ values for compound 7b, supporting potent inhibition of CYP51-dependent sterol conversion at the cellular level. Cytotoxicity assessment in mammalian cell lines (HepG2, HK2, and Vero) indicated that compound 7b possessed lower cytotoxicity and a more favourable selectivity profile than ketoconazole. Molecular docking studies revealed favourable binding interactions of compound 7b within the CYP51 active site, while 100 ns molecular dynamics simulations supplemented by MM–PBSA energy decomposition and hydrogen-bond occupancy analysis supported persistent non-covalent stabilisation of the ligand–protein complex. Collectively, the integration of synthetic chemistry, antifungal evaluation, cellular sterol profiling, and complementary computational modelling identifies compound 7b as a promising antifungal lead scaffold associated with disruption of CYP51-dependent ergosterol biosynthesis.