The Cytochalasins and Polyketides from a Mangrove Endophytic Fungus Xylaria arbuscula QYF

Twelve compounds, including four undescribed cytochalasins, xylariachalasins A-D (<b>1</b>-<b>4</b>), four undescribed polyketides (<b>5</b>-<b>8</b>), and four known cytochalasins (<b>9</b>-<b>12</b>), were isolated from the mangrove endophytic fungus <i>Xylaria arbuscula</i> QYF. Their structures and absolute configurations were established by extensive spectroscopic analyses (1D and 2D NMR, HRESIMS), electronic circular dichroism (ECD) calculations, ¹³C NMR calculation and DP4+ analysis, single-crystal X-ray diffraction, and the modified Mosher ester method. Compounds <b>1</b> and <b>2</b> are rare cytochalasin hydroperoxides. In bioactivity assays, Compound <b>2</b> exhibited moderate antimicrobial activities against <i>Staphylococcus aureus</i> and <i>Candida albicans</i> with MIC values of 12.5 μM for both Compound <b>10</b> exhibited significant cytotoxic activity against MDA-MB-435 with an IC₅₀ value of 3.61 ± 1.60 μM.