Design, synthesis, and biological evaluation of selenium-containing small molecule compounds based on the dual mechanism of fungal CYP51 inhibition and fungal ROS generation

Abstract

Herein, we modified our previously published miconazole analogue containing selenium A03 of fungal CYP51 (belongs to the cytochrome P450 monooxygenase (CYP) superfamily) inhibitors to obtain novel analogues with inhibitory effects on multiple fungal pathogens, but also with a novel mechanism of action such as inducing fungal ROS (reactive oxygen species) generation. Firstly, three novel series of selenium-containing azole derivatives were prepared to determine their antifungal activity against common test fungal strains and fluconazole-resistant strains. Among all the novel derivatives, compounds B06, B11 and B14 with excellent antifungal activity (0.03-4 µg/mL) can inhibit the fluconazole-resistant Candida Strain 17#, CaR, 632, 901 and 904 in the range of MIC (minimal inhibitory concentrations) values (0.25–16 µg/mL). Antifungal mechanism studies revealed representative compounds not only had dose-dependent inhibitory activity of CYP51 but also down-regulated the expression of resistance-associated genes. Interestingly, representative compound B11 could also promote the generation of ROS. Therefore, the MIC values of Candida albicans (SC5314) inhibited by B11 and C06 in the presence of different concentrations of antioxidant NAC (N-acetyl-L-cysteine) were measured to further verify the synergistic antifungal effect between the mechanism promoting fungal ROS production and CYP51 inhibitory activity. Meanwhile, the results of cytotoxic evaluation showed that representative compounds were at the same level as that of miconazole with IC50 of 8.61∼29.91 µM, suggesting that the toxicity of the target compounds did not increase after the introduction of selenium atoms. Moreover, the in vitro stability assays also indicated our developed compounds possessed better liver microsomal metabolic stabilities (T1/2=14.9–20.1 min) compared with miconazole (T1/2=8.3 min). And representative compound B11 also displayed stability in rat plasma (T1/2>360 min). In addition, the docking results showed that the binding modes of target compounds B06, B11 and C06 to Candida albicans CYP51 were almost the same as those of miconazole. Overall, the selenium-containing small molecule compounds with dual mechanism can be further developed for the potential treatment of invasive fungal infections.