Cytotoxic Bromine- and Iodine-Containing Cytochalasins Produced by the Mangrove Endophytic Fungus Phomopsis sp. QYM-13 Using the OSMAC Approach

Twelve new cytochalasins, phomopchalasins D–O (1–3, 5–12, and 14), including one brominated (2) and two iodinated cytochalasins (3 and 6), together with six known analogues (4, 13, and 15–18) were isolated from the mangrove-derived fungus Phomopsis sp. QYM-13 treated with 3% NaBr or 3% KI in potato liquid medium. Their structures and absolute configurations were established by extensive spectroscopic analysis (1D and 2D NMR, HRESIMS), electronic circular dichroism calculations, and a single-crystal X-ray diffraction experiment. Compounds 3 and 6 represent the first iodinated cytochalasins. Compounds 2, 15, 17, and 18 exhibited significant cytotoxicity against human cancer cell line MDA-MB-435 with IC50 values ranging from 0.2 to 8.2 μM.