Design and Synthesis of Evolitrine Derivatives and Their Antifungal Activities In Vitro and In vivo

Guided by our previous finding of its antifungal activity, 46 derivatives of evolitrine (from Orixa japonica) were designed and synthesized to develop new fungicide candidates. Their structures were confirmed via NMR, HRMS, and X-ray crystallography. Antifungal activity results indicated that C2 exhibited broad-spectrum activities against six plant fungi. Particularly, C2 showed remarkable antifungal activity on Verticillium dahliae (EC50 = 2.31 μg/mL), a 7-fold improvement over evolitrine (EC50 = 16.5 μg/mL). Mechanistic studies revealed that C2 disrupts hyphal integrity and induces lipid peroxidation, evidenced by SEM, TEM, and MDA assays. Additionally, C2 significantly downregulated genes in cyanoamino acid, starch/sucrose, and phenylalanine metabolism. Furthermore, C2 exhibited moderate control efficacy (36.4-54.4%) against verticillium wilt on eggplant and tomato at 200 μg/mL and was nontoxic to seedlings of eggplant/tomato and seeds of adzuki beans/mung beans. These findings indicated that C2 could be considered a potent novel antifungal candidate.