A novel 4-pyridone alkaloid derivative, microsphaerone H (1), and a new polyketide, annularin O (2), were isolated alongside 17 known compounds (3-19) from an endophytic fungus Penicillium citreosulfuratum YFC-1 of Sphagneticola trilobata. Compounds 4 and 5 were newly identified here as natural products. Their structural elucidation, inclusive of absolute configurations, was achieved via integrated spectroscopic and quantum chemical ECD methodologies. All isolates (1-19) were evaluated for their anti-inflammatory activities. Compounds 4-6, 8, and 13 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 µM, respectively.
Chen et al. (Tue,) studied this question.