Novel Sulfonamide Derivatives Containing a Piperidine Moiety as New Bactericide Leads for Managing Plant Bacterial Diseases

Plant bacterial diseases are an intractable problem due to the fact that phytopathogens have acquired strong resistances for traditional pesticides, resulting in restricting the quality and yield of agricultural products around the world. To develop new agrochemical alternatives, we prepared a novel series of sulfanilamide derivatives containing piperidine fragments and assessed their antibacterial potency. The bioassay results revealed that most molecules displayed excellent in vitro antibacterial potency towards Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas axonopodis pv. citri (Xac). In particular, molecule C(4) exhibited outstanding inhibitory activity toward Xoo with EC(50) value of 2.02 µg mL(−1), which was significantly better than those of the commercial agents bismerthiazol (EC(50) = 42.38 µg mL(−1)) and thiodiazole copper (EC(50) = 64.50 µg mL(−1)). A series of biochemical assays confirmed that compound C(4) interacted with dihydropteroate synthase, and irreversibly damaged the cell membrane. In vivo assays showed that the molecule C(4) presented acceptable curative and protection activities of 34.78% and 39.83%, respectively, at 200 µg mL(−1), which were greater than those of thiodiazole and bismerthiazol. This study highlights the valuable insights for the excavation and development of new bactericides that can concurrently target dihydropteroate synthase and bacterial cell membranes.