Studies on secondary metabolites and anti-inflammatory activity of fungus <i>Penicillium citreosulfuratum</i> YFC-1 from <i>Sphagneticola trilobata</i>

A novel 4-pyridone alkaloid derivative, microsphaerone H (<b>1</b>), and a new polyketide, annularin O (<b>2</b>), were isolated alongside 17 known compounds (<b>3-19</b>) from an endophytic fungus <i>Penicillium citreosulfuratum</i> YFC-1 of <i>Sphagneticola trilobata</i>. Compounds <b>4</b> and <b>5</b> were newly identified here as natural products. Their structural elucidation, inclusive of absolute configurations, was achieved <i>via</i> integrated spectroscopic and quantum chemical ECD methodologies. All isolates (<b>1-19</b>) were evaluated for their anti-inflammatory activities. Compounds <b>4-6</b>, <b>8</b>, and <b>13</b> suppressed LPS-induced nitric oxide (NO) production in RAW 264.7 macrophages, displaying IC₅₀ values of 29.72, 17.99, 49.88, 31.38, and 28.23 <i>µ</i>M, respectively.