Antifungalagent 135 (Compound C2) is an antifungal agent that functions as a succinate dehydrogenase (SDH) inhibitor with an IC50 of 1.99 μM. It demonstrates potent antifungal efficacy against Valsa mali, Sclerotinia sclerotiorum, and Phytophthora capsici, with EC50 values of 0.280 mg/L, 1.11 mg/L, and 0.130 mg/L, respectively. This compound provides protective and therapeutic effects on P. capsici and V. mali by effectively disrupting mycelial structural integrity and inhibiting mycelial growth.