Inspired by natural 2-quinolinecarboxylic acid derivatives, a series of quinoline compounds containing acylhydrazine, acylhydrazone, sulfonylhydrazine, oxadiazole, thiadiazole, or triazole moieties were synthesized and evaluated for their fungicidal activity. Most of these compounds exhibited excellent fungicidal activity in vitro. Significantly, compound 2e displayed the superior in vitro antifungal activity against Sclerotinia sclerotiorum, Rhizoctonia solani, Botrytis cinerea, and Fusarium graminearum with the EC 50 values of 0.39, 0.46, 0.19, and 0.18 μg/mL, respectively, and were more potent than those of carbendazim (EC 50 , 0.68, 0.14, >100, and 0.65 μg/mL, respectively). Moreover, compound 2e could inhibit spore germination of F. graminearum. Preliminary mechanistic studies showed that compound 2e could cause abnormal morphology of cell walls and vacuoles, loss of mitochondrion, increases in membrane permeability, and release of cellular contents. These results indicate that compound 2e displayed superior fungicidal activities and could be a potential fungicidal candidate against plant fungal diseases.

Phytopathogenic fungi have become a serious threat to the quality of agricultural products, food security and human health globally, necessitating the need to discover new antifungal agents with de novo chemical scaffolds and high efficiency.