Antimicrobial evaluation and action mechanism of chalcone derivatives containing quinoxaline moiety

A series of chalcone derivatives containing quinoxaline moieties were synthesized, and their antibacterial activities were evaluated. Antibacterial bioassays indicated that some of the compounds exhibited significant antibacterial activity against Xanthomonas axonopodis pv. Citri (Xac), Xanthomonas oryzae pv. oryzae (Xoo), and Ralstonia solanacearum (Rs) at the concentrations of 50 or 100 μg/cm3. 50% effective concentration (EC50) values of (E)-3-(pyridin-2-yl)-1-[4-(quinoxalin-2-yloxy)phenyl]prop-2-en-1-one against Xac, Xoo, and Rs were 6.72, 15.17, and 9.29 μg/cm3, respectively, which were better than those of bismerthiazol (44.31, 42.46, and 62.36 μg/cm3, respectively). Scanning electron microscopy (SEM) was employed to analyze the mechanism of antibacterial action of that compound toward Xac.