Discovery of Novel Stilbene-Containing Nicotinamide Derivatives as Potential SDHIs against Rhizoctonia solani and Sclerotinia sclerotiorum

Abstract As part of an ongoing effort to develop novel succinate dehydrogenase inhibitors (SDHIs), a range of innovative nicotinamide derivatives featuring stilbene scaffolds were synthesized and assessed for their antifungal properties. Lead compounds 6g and 6c demonstrated significant antifungal efficacies against Rhizoctonia solani and Sclerotinia sclerotiorum, with EC50 (half maximal effective concentration) values of 0.008 and 0.034 μg/mL, respectively, surpassing Boscalid (EC50 = 0.573 and 0.455 μg/mL, respectively) and Fluxapyroxad (EC50 = 0.026 and 0.037 μg/mL, respectively). Detached leaf assays further confirmed their excellent protective and curative effects, outperforming Boscalid and Fluxapyroxad. Further studies revealed that compound 6g operated through a mechanism akin to Boscalid and Fluxapyroxad. These results indicated that both 6g and 6c showed great potential as novel SDHIs for effectively managing R. solani and S. sclerotiorum, underscoring the necessity for further research to fully explore their capabilities.