Isoflavones and Stilbenes With Antifungal Activities From the Seeds of Thermopsis lanceolata R. Br

In order to discover novel fungicides from natural products, the phytochemical investigation of Thermopsis lanceolata seeds was thoroughly conducted. Eight new isoflavone derivatives (1-5 and 8-10), two new stilbenes (6 and 7), as well as 21 known isoflavones (11-31) were obtained from the crude extract of T. lanceolata seeds following a bioassay-guided method. The structures of 1-31 were confirmed via HRESIMS, NMR, IR, UV, and quantum chemistry calculations. The antifungal activities of 1-31 against Phytophthora nicotiana, Colletotrichum orbiculare, Rhizoctonia solani, and Botrytis cinerea were screened according to the mycelial inhibition test. Compound 6 displayed significant antifungal activity against B. cinerea in vitro (EC₅₀: 9.68 μg/mL) and had an 8 5.7% prevention and control effect in vivo (100 μg/mL). Moreover, antifungal mechanism studies revealed that 6 causes the accumulation of reactive oxygen species, increases the level of lipid peroxidation, decreases the activity of MDH, and finally triggers molecular damage and cell death in vitro. Therefore, 6 can be utilized as a lead compound for novel fungicides.