Chemical preparation, biological evaluation and 3D-QSAR of ethoxysulfuron derivatives as novel antifungal agents targeting acetohydroxyacid synthase

Article abstract of DOI:10.1016/j.ejmech.2018.11.005

Accetohydroxyacid synthase (AHAS) is the first enzyme involved in the biosynthetic pathway of branched-chain amino acids. Earlier gene mutation of Candida albicans in a mouse model suggested that this enzyme is a promising target of antifungals. Recent studies have demonstrated that some commercial AHAS-inhibiting sulfonylurea herbicides exerted desirable antifungal activity. In this study, we have designed and synthesized 68 novel ethoxysulfulron (ES) derivatives and evaluated their inhibition constants (K_i) against C. albicans AHAS and cell based minimum inhibitory concentration (MIC) values. The target compounds 5-1, 5-10, 5-22, 5-31 and 5-37 displayed stronger AHAS inhibitions than ES did. Compound 5-1 had the best K_i of 6.7 nM against fungal AHAS and MIC values of 2.5 mg/L against Candida albicans and Candica parapsilosis after 72 h. A suitable nematode model was established here and the antifungal activity of 5-1 was further evaluated in vivo. A possible binding mode was simulated via molecular docking and a comparative field analysis (CoMFA) model was constructed to understand the structure-activity relationship. The current study has indicated that some ES derivatives should be considered as promising hits to develop antifungal drugs with novel biological target.