Isoflavones and Stilbenes With Antifungal Activities From the Seeds of <i>Thermopsis lanceolata</i> R. Br

In order to discover novel fungicides from natural products, the phytochemical investigation of <i>Thermopsis lanceolata</i> seeds was thoroughly conducted. Eight new isoflavone derivatives (<b>1-5</b> and <b>8-10</b>), two new stilbenes (<b>6</b> and <b>7</b>), as well as 21 known isoflavones (<b>11-31</b>) were obtained from the crude extract of <i>T. lanceolata</i> seeds following a bioassay-guided method. The structures of <b>1-31</b> were confirmed via HRESIMS, NMR, IR, UV, and quantum chemistry calculations. The antifungal activities of <b>1-31</b> against <i>Phytophthora nicotiana</i>, <i>Colletotrichum orbiculare</i>, <i>Rhizoctonia solani</i>, and <i>Botrytis cinerea</i> were screened according to the mycelial inhibition test. Compound <b>6</b> displayed significant antifungal activity against <i>B. cinerea</i> 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 <b>6</b> 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, <b>6</b> can be utilized as a lead compound for novel fungicides.