Synthesis and Antifungal Activity of Aldehydes‐Thiourea Derivatives as Promising Antifungal Agents Against Postharvest Gray Mold Disease

Gray mold disease is caused by Botrytis cinerea, which could severely reduce the production yield and quality of tomatoes. To explore more potential fungicides with new scaffolds for controlling gray mold disease, 10 aldehydes-thiourea derivatives were designed, synthesized, and assayed for inhibitory activity against three plant pathogenic fungi. The preliminary antifungal assay suggested that some title derivatives showed moderate to good antifungal activity against B. cinerea. In particular, compound 9 presented excellent in vitro antifungal activity against B. cinerea (half maximal effective concentration [EC₅₀] = 0.70 mg/L), which was superior to boscalid (EC₅₀ = 1.41 mg/L). In vivo antifungal assay indicated 9 displayed good protective effects on tomato leaves infected by B. cinerea. A preliminary mechanism study displayed that 9 could damage the surface morphology, increase the cell membrane permeability, and lead to the increase of reactive oxygen species level. Enzyme inhibition assay illustrated that 9 could be a potential laccase inhibitor. The above bioassay results and mechanism investigation demonstrated that aldehydes-thiourea derivatives could be promising fungicides for further controlling postharvest gray mold disease, which would be potential candidates for fungicidal compounds.