Beyond Monomers: Discovery of Bioactive Naphthoquinone Heterodimers and Perenniporides from Pyrenochaetopsis Species

Naphthoquinones can be found in Nature in various formats, both as standalone molecules and as building blocks for larger structures. A study of the fungus, Pyrenochaetopsis sp. (strain MSX63699), led to the isolation of naphthoquinone analogues (1-21), including both monomers and heterodimers and seven new compounds─three kirschsteinin analogues (11-13) and four perenniporides (18-21). The structures of these were elucidated through analysis of data from 1D and 2D NMR, HRESIMS, and ECD experiments, and several compounds displayed cytotoxic activity against melanoma (MDA-MB-435) and ovarian (OVCAR3) cancer cell lines, with structure-activity trends suggesting key roles for specific substituents in enhancing bioactivity. Notably, compounds 3-6, 9, 11, 15, and 19-20 had IC₅₀ values that ranged from about 1 to 5 μM against both cell lines. Overall, this work expands the chemical diversity of fungal naphthoquinones by identifying new heterodimeric and perenniporide-type analogues and underscores the untapped biosynthetic potential of the Pyrenochaetopsis species.