Novel Cinnamic Acid Derivatives Containing the 1,3,4-Oxadiazole Moiety: Design, Synthesis, Antibacterial Activities, and Mechanisms

There is a lack of effective antibacterial
agents against rice
bacterial leaf streak and leaf blight. Cinnamic acid derivatives containing
the 1,3,4-oxadiazole moiety were synthesized, and their antibacterial
activities against Xanthomonas oryzae pv. oryzicola (Xoc) and X. oryzae pv. oryzae (Xoo) were evaluated. Based on the three-dimensional quantitative structure–activity
relationship (3D-QSAR) model, compound 31 with better
antibacterial activity against Xoc was designed and
synthesized, and the 50% effective concentration (EC50)
value was 0.2 mg/L. The curative and protective activities of compound 31 against rice bacterial leaf streak at 100 mg/L were 39.5
and 35.4%, respectively, which were higher than those of thiodiazole
copper (28.4 and 20.7%, respectively). The antibacterial activity
of compound 31 against rice bacterial leaf streak is
closely associated with the activity of related defensive enzymes
and the increase in glutathione metabolism.