Diverse metabolites of the plant endophytic fungus Diaporthe hubeiensis ZMU-49-3 and their antifungal activities against Bipolaris sorokiniana

Phytopathogenic fungi, particularly Bipolaris sorokiniana, pose severe threats to global agricultural production and food security. Microbial secondary metabolites, especially those from endophytic fungi, represent promising sources for novel antifungal agents. This study systematically investigated the secondary metabolites of the endophytic fungus Diaporthe hubeiensis ZMU-49-3, isolated from the leaves of Acacia confusa Merr. An investigation of D. hubeiensis ZMU-49-3 led to the isolation of fifteen secondary metabolites (1–15), including four new tetrahydrochromone derivatives diaporthanones A–D (1–4), two new polyketide derivatives diaporthenoic acid A (6) and diaporthenolide A (7), and a new dibenzoxepane derivative diaporthoxepane A (8). Their structures and absolute configurations were determined via comprehensive spectroscopic analysis, electronic circular dichroism (ECD) calculations, and DP4⁺ probability analyses. Subsequent in vitro antifungal screening revealed that compound 4 exhibited the highest inhibitory activity against B. sorokiniana, with a minimum inhibitory concentration (MIC) of 10 μg/mL. The MICs of compounds 2 and 5 were 40 and 60 μg/mL, respectively. Scanning electron microscopy (SEM) indicated that compound 4 disrupted the mycelial structure. These findings increase the chemical diversity of Diaporthe species and suggest that the tetrahydrochromone scaffold represents a promising template for the development of potential antifungal agents. Fifteen metabolites were isolated from Diaporthe hubeiensis ZMU-49-3, including seven new compounds. Structures and absolute configurations were determined by spectroscopy, ECD calculations, NMR-based DP4+ analysis. New compound 4 showed potent antifungal activity against Bipolaris sorokiniana with an MIC of 10 μg/mL. SEM analysis revealed that compound 4 disrupts the mycelial structure.