Abstract

As a devastating disease worldwide, rice bacterial leaf blight—caused by Xanthomonas oryzae pv. oryzae (Xoo)—leads to substantial reductions in grain yield. The increasing resistance to conventional bactericides necessitates the development of novel and sustainable control agents. This study evaluated 58 novel alkyl sulfonamide compounds against Xoo. In the turbidimetric assay at 100 mg/L, several compounds showed potent antibacterial activity. Among them, SYAUP-116 and SYAUP-212 exhibited in vitro inhibition comparable to that of streptomycin sulfate at the same concentration. Furthermore, in EC50 determination assays, both compounds yielded lower EC50 values than zinc thiazole. Among the 58 compounds tested, SYAUP-491 exhibited an in vitro EC50 of 6.96 mg/L and achieved 74.1% in vivo therapeutic efficacy at 200 mg/L, representing the most promising lead for further characterization. Molecular docking, based on prior proteomic data, indicates potential stable binding to ribosomal proteins (50S L33/L34 and 30S S5), with the strongest interaction observed for L33 (binding free energy: −5.73 kcal/mol). This suggests a putative mechanism involving ribosome targeting and protein synthesis inhibition, which may be facilitated by hydrophobic interactions and halogen bonds derived from its trifluoromethyl and sulfonamide groups. SYAUP-491 demonstrates significant potential as a novel bactericide for rice bacterial leaf blight, warranting further research on structure-activity optimization, target validation, and field performance.

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