Eremophilane-Type Sesquiterpenoids with Diverse Skeletons from Ligularia sagitta

Five new highly oxygenated eremophilane-type sesquiterpenoids, possessing C-19 (1 and 2), C-15 (3 and 4), and C-14 (8) skeletons, along with eight known eremophilenolides were obtained from the aerial parts of Ligularia sagitta. The absolute configuration of 1 was assigned by X-ray diffraction analysis and that of 3 by ECD spectroscopy. Compounds 1-10 were evaluated for their antibacterial activities against Staphyloccocus aureus, Bacillus subtilis, Escherichia colt, Bacillus cereus, and Erwinia carotovora. Compounds 4 and 5 displayed broad-spectrum inhibitory activity against these bacteria with MIC values of approximately 7.25 mu g/mL, followed by 3 and 6 with MIC values in the range of 23.0-125.0 mu g/mL. Compounds 3 and 8 showed mild activity against three human tumor cell lines (IC50 approximate to 13 mu M). Preliminary structure activity relationships for these eremophilenolides are reported.