Design, synthesis and biological evaluation of novel 5-(piperazin-1-yl)quinolin-2(1H)-one derivatives as potential chitin synthase inhibitors and antifungal agents

A series of 5-(4-substituted piperazin-1-yl)quinolin-2(1H)-one derivatives (4a-4w) has been designed as chitin synthase inhibitors and antifungal agents. The designed compounds were obtained by an environmentally benign route in four steps starting from 5-amino-3,4-dihydroquinolin-2(1H)-one which was offered by an easily achieved synthetic method. The synthesized compounds were tested for their inhibition potency against chitin synthase. Compounds 4a and 4c exhibited excellent inhibitory activity with IC50 values of 0.10 mM and 0.15 mM, respectively, which is better than that of Polyoxin B whose IC50 value is 0.18 mM. Compounds 4h, 4i, 4j, 4k and 4n exerted moderate inhibition potency with IC50 values of 0.38, 0.36, 0.47, 0.47 and 0.37 mM, respectively. These synthesized compounds were also evaluated for their in vitro antifungal activity against Candida albicans, Crytococcus neoformans, and Aspergillus flavus. Compounds 4a, 4i and 4j exhibited the most potent antifungal activity against C. albicans with MIC of 32 μg/mL, which were similar to that of Polyoxin B. The results of antibacterial activity against selected strains showed that the designed compounds have little potency against bacteria and indicated that these compounds were chitin synthase inhibitors and have selectively antifungal activity.