Design, synthesis, and biological evaluation of disulfides based on garlic extract against rice bacterial leaf blight caused by Pantoea ananatis.

Background: Rice, a staple food crop for half of the global population, faces severe threats from bacterial leaf blight caused by the pathogen Pantoea ananatis. The conventional chemical control strategy poses significant environmental risks and contributes to resistance development, thus necessitating the discovery of eco-friendly antimicrobial agents with enhanced cost-effectiveness. Although disulfides derived from garlic exhibit broad-spectrum antibacterial activity, their molecular instability limits practical applications. This study aimed to design and synthesize disulfide derivatives with improved stability and evaluate their inhibitory potential against P. ananatis.

Results: In this study, 41 disulfides were successfully synthesized. Among them, compound D7 demonstrated the strongest inhibitory activity against P. ananatis with a half-maximal effective concentration (EC) value of 0.87 μg/mL, markedly surpassing the control agent Zhongshengmycin, which exhibited an EC value of 14.73 μg/mL. Mechanistic studies revealed that D7 disrupts the bacterial oxidative defense system by inducing reactive oxygen species accumulation and inhibiting superoxide dismutase and catalase activities, thereby triggering apoptosis. Electron microscopy observations confirmed that D7 causes membrane disintegration and cytoplasmic leakage. In vivo experiments demonstrated that D7 (200 μg/mL) achieved 77.50% curative and 79.49% protective efficacy against rice bacterial leaf blight, with low acute toxicity observed in non-target organisms.

Conclusion: This study confirms that compound D7 efficiently suppresses P. ananatis and treatment bacterial leaf blight via dual oxidative stress and membrane damage mechanisms, while also posing low environmental risks. © 2025 Society of Chemical Industry.