Structural Simplification of Cryptolepine to Obtain Novel Antifungal Quinoline Derivatives against Phytopathogenic Fungi.

A series of quinoline derivatives were designed and synthesized by the structural simplification of cryptolepine and evaluated for their fungicidal activity against six phytopathogenic fungi. Most of these compounds exhibited remarkable activities against . Among them, compounds and showed superior antifungal activity. Significantly, compared to cryptolepine, compound exhibited broad-spectrum inhibitory activities against , , , , , and with the respective EC values of 0.249, 1.569, 3.915, 0.505, 0.246, and 4.999 μg/mL. Compound displayed the best antifungal activity against with an EC value of 0.156 μg/mL. Preliminary mechanistic studies showed that compound could inhibit spore germination, affect the permeability of the cell membrane, increase the content of reactive oxygen species, and affect the morphology of hyphae and cells. Moreover, compound showed excellent protective effect against , which was more potent than pyrimethanil and equitant to cryptolepine. These results evidenced that compound displayed superior fungicidal activities and could be a potential fungicidal candidate against plant fungal diseases.