Design and synthesis novel amide derivatives containing an 1,3,4-oxadiazole moiety as potential antibacterial agents

To find new antibacterial agents, 25 novel amide derivatives containing an 1,3,4-oxadiazole moiety were designed and synthesized, and their antibacterial activity against Xanthomonas oryzae pv. oryzicola (Xoc) and Xanthomonas oryzae pv. oryzae (Xoo) were tested. Interestingly, all target compounds showed excellent antibacterial activities against Xoc and Xoo. The EC50 values of compounds 1-25 against Xoc and Xoo were 1.2-4.0 mg/L and 0.5-2.3 mg/L, respectively, which were significantly superior to those of the thiodiazole copper (95.1 and 89.0 mg/L) and bismerthhibol (73.8 and 68.8 mg/L). For example, the EC50 values of compound 16 against Xoc and Xoo were 1.7 and 0.5 mg/L, respectively. Meanwhile, the curative and protection activity of compound 16 against rice bacterial leaf blight were 42.4% and 42.1%, respectively, which were superior to the control of jiahuangxianjunzuo (34.1% and 32.6%) and thiodiazole copper (33.0% and 27.1%). In addition, compound 16 might suppress the cell growth of Xoo by inhibiting the production of extracellular polysaccharide, the formation of biofilm, changes the cell membrane permeability, and cell surface morphology.