Design, Synthesis, Antibacterial Activity Evaluation, and Mechanism of Action Study of Novel Sulfonamide-Containing Phosphonate Derivatives

Pesticide resistance in plant bacterial pathogens necessitates new antibiotic alternatives. Herein, novel sulfonamide-containing phosphonate compounds were synthesized, with their antibacterial activity and mechanism systematically investigated. Bioassays showed that compound A2 exhibited the strongest activity against Xanthomonas oryzae pv oryzae (Xoo), with an EC₅₀ of 9.9 μg/mL. Mechanistic studies revealed that A2 disrupts bacterial cell membrane integrity (via SEM and EC measurements), enhances host resistance by upregulating catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) activities, and dysregulates proteins involved in streptomycin biosynthesis, purine metabolism, and ribosomal pathways, thereby inhibiting bacterial protein synthesis and inducing cell death. These findings highlight sulfonamide-containing phosphonates as promising antibacterial agents against plant bacterial diseases.