Design, synthesis and bioactivity of benzoxazinone-containing formononetin derivatives

Phytopathogens have long compromised the yield and quality of crops worldwide, and the overuse of conventional synthetic pesticides has engendered a series of ecological and environmental issues. Consequently, the development of low-toxicity, high-efficacy and environmentally benign pesticides has become an urgent imperative.

Using the natural product formononetin as starting material, a series of formononetin derivatives bearing benzoxazinone moiety were designed and synthesized, and their in vitro antifungal activities against 10 phytopathogenic fungi were evaluated. The results revealed that J21 exhibited the most potent inhibitory effect against Phomopsis sp. (Ps), with a median effective concentration (EC₅₀) of 7.58 μg mL^-1, which was significantly superior to that of the commercial fungicide azoxystrobin (Az, 30.32 μg mL^-1). In in vivo antifungal assays, at a concentration of 200 μg mL^-1 J21 displayed curative and protective activities of 56.1% and 66.8% against kiwifruit soft rot, respectively, outperforming Az (47.8% and 63.3%). Mechanistic investigations demonstrated that J21 induces morphological deformation and damage to hyphae, disrupts cell membrane integrity, triggers oxidative stress and interferes with normal physiological metabolism of the pathogen. Density functional theory (DFT) calculations further indicated that J21 possesses favorable electronic structural properties.

J21 displays promising antifungal activity and represents a potential lead compound for antifungal development. © 2026 Society of Chemical Industry.