Antibacterial Activities of Novel Dithiocarbamate-Containing 4H-Chromen-4-one Derivatives

To aid the development of novel antibacterial agents that possess a innovative mechanism of action, we built a series of novel dithiocarbamate-containing 4H-chromen-4-one derivatives. We evaluated the activities of the derivatives against three plant pathogens Xanthomonas oryzae pv oryzae (X. oryzae pv o.), Ralstonia solanacearum (R. solanacearum), and Xanthomonas axonopodis pv citri (X. axonopodis pv c.). The results of the antibacterial bioassay showed that most of the target compounds displayed good inhibitory effects against X. oryzae pv o. and X. axonopodis pv c. Remarkably, compound E6 showed the best in vitro antibacterial activity against X. axonopodis pv c., with an EC₅₀ value of 0.11 μg/mL, which was better than those of thiodiazole copper (59.97 μg/mL) and bismerthiazol (48.93 μg/mL). Compound E14 exhibited the best in vitro antibacterial activity against X. oryzae pv o., with an EC₅₀ value of 1.58 μg/mL, which was better than those of thiodiazole copper (83.04 μg/mL) and bismerthiazol (56.05 μg/mL). Scanning electron microscopy analysis demonstrated that compounds E6 and E14 caused the rupture or deformation of the cell membranes for X. axonopodis pv c. and X. oryzae pv o., respectively. In vivo antibacterial activity test and the defensive enzymes activity test results indicated that the compound E14 could reduce X. oryzae pv o. more effectively than thiodiazole-copper or bismerthiazol.