Beyond Monomers: Discovery of Bioactive Naphthoquinone Heterodimers and Perenniporides from <i>Pyrenochaetopsis</i> 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, <i>Pyrenochaetopsis</i> sp. (strain MSX63699), led to the isolation of naphthoquinone analogues (<b>1</b>-<b>21</b>), including both monomers and heterodimers and seven new compounds─three kirschsteinin analogues (<b>11</b>-<b>13</b>) and four perenniporides (<b>18</b>-<b>21</b>). 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 <b>3</b>-<b>6</b>, <b>9</b>, <b>11</b>, <b>15</b>, and <b>19-20</b> 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 <i>Pyrenochaetopsis</i> species.