Antioomycete activity and mechanism of neoechinulin A from the marine fungus Aspergillus amstelodami 012393 against Phytophthora capsici : neoechinulin A against Phytophthora capsici

Abstract BACKGROUND Phytophthora capsici , a highly destructive pathogen affecting solanaceous and cucurbitaceous crops globally, poses a significant threat to agricultural production and food security. Neoechinulin A (NEA), an isoprenyl indole alkaloid, was previously known for its anti‐inflammatory properties, but had not been reported for its antioomycete effects. RESULTS NEA demonstrated potent antioomycete activity against P. capsici , with an EC 50 value of 21.95 μg/mL. In vitro and in vivo assays demonstrated that NEA effectively inhibited mycelial growth, sporangium formation, and zoospore motility of P. capsici mycelium, while also enhancing the protective capacity of pepper plants. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that NEA caused significant morphological alterations in P. capsici filaments, leading to the disruption of cell membrane integrity, vacuole swelling and rupture of the vacuolar membrane, severe plasmolysis, along with the disappearance of most organelles. Moreover, NEA induced an increase of malondialdehyde (MDA) content in P. capsici mycelium, accompanied by a reduction in the activities of antioxidant enzymes and a decrease in soluble protein levels. Transcriptome data analysis revealed that NEA affected the expression of genes involved in glycolysis/gluconeogenesis, pyruvate metabolism, and glutathione metabolism, which resulted in a reduction of pyruvate, ATP, and glutathione (GSH) levels, thereby disrupting energy metabolism and causing cellular dysfunction in P. capsici . CONCLUSION These findings indicated that NEA could effectively control diseases caused by P. capsici and showed promise as a potential novel fungicide for managing Phytophthora blight. © 2025 Society of Chemical Industry.