Synthesis and antifungal activity of aldehydes‐thiourea derivatives as promising antifungal agents against postharvest gray mold disease

Gray mold disease is caused by B. cinerea, which could severely reduce the production yield and quality of tomatoes. To explore more potential fungicides with new scaffolds for controlling the gray mold disease, ten aldehydes‐thiourea derivatives were designed, synthesized and assayed for inhibitory activity against three plant pathogenic fungi. The preliminary antifungal assay suggested that the some title derivatives showed moderate to good antifungal activity against Botrytis cinerea. Especially, compound 9 presented excellent in vitro antifungal activity against B. cinerea (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. 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 (ROS) level. Enzyme inhibition assay illustrated that 9 could be potential laccase inhibitor. The above bioassay results and mechanism investigation demonstrated that aldehydes‐thiourea derivatives could be promising fungicide for further controlling postharvest gray mold disease, which would be potential candidate of fungicidal compound.