Two ergostane-type steroids from the endophytic fungus Phomopsis sp. ZM-1.

Two undescribed ergostane-type steroids, phomopsteroids A and B (1 and 2), along with six known analogues (3-8), were isolated from the endophytic fungus Phomopsis sp. ZM-1. Structurally, compounds 1 and 2 feature an unprecedented 6,7-seco tricyclic carbon framework. Their structures and absolute configurations were unambiguously elucidated using comprehensive spectroscopic analyses, including HRESIMS, NMR, and UV spectroscopy, supplemented by electronic circular dichroism (ECD). Compound 6 exhibited a notable cytotoxic effect against A549 human lung carcinoma cells, with an IC50 value of 7.21 μM.