Design, Synthesis, Antibacterial Activity, and Antivirulence Factor of Novel 1,2,4-Thiadiazole Derivatives Containing an Amide Moiety

To develop antibacterial agents with novel mechanisms of action, a series of novel 1,2,4-thiadiazole derivatives containing amide structures were designed and synthesized. The antibacterial activities of derivatives against Xanthomonas oryzae pv. oryzicola (Xoc), Xanthomonas oryzae pv. oryzae (Xoo), and Pseudomonas syringae pv. actinidiae (Psa) were evaluated, and all derivatives were exhibited excellent antibacterial activities. Among them, compound Z4 demonstrated significant antibacterial activities against Xoo, Xoc, and Psa, with EC50 values of 0.32, 0.43, and 11.06 mg/L, respectively. Compound Z4 exhibited a protective activity of 49.42% and a curative activity of 44.93% against rice bacterial leaf blight. In addition, compound Z4 could inhibit pathogenic bacteria by inhibiting a variety of virulence factors (exopolysaccharides, biofilms, motility, and extracellular enzymes). Compound Z4 stimulated the biochemical process of rice self-defense signaling by affecting cell transcription and translation and induced rice self-defense genes and controlled hypersensitivity reactions to resist pathogen infection.