Novel Sesquiterpenes from Ligularia virgaurea spp. oligocephala

Two novel sesquiterpene dimers, ligularin A (1) and ligulolide D (2), and one new sesquiterpenoid, 1b,10a-dihydroxy-6b-[(2-methylpropyl)oxy]furanoeremophil-9-one (3), as well as two known sesquiterpenoids, 6b-[(2-methylpropyl)oxy]-furanoeremophil-1(10)-en-9-one (4) and 1-hydroxy-3,7-dimethyl-2-(pent-3-enyl)benzofuran (5), were isolated from the petroleum-ether fraction from an alcoholic extract of the whole plant of Ligularia virgaurea spp. oligocephala. Their structures were elucidated by 1D and 2D-NMR spectroscopy together with HR-ESI-MS analysis, and comparison of the spectroscopic data with those reported for structurally related compounds. In addition, the cytotoxicities against human gastric cancer SGC-7910 cell were measured in vitro, the results demonstrated that these sesquiterpenes have no cytotoxicity against the selected tumor cell (all IC50 values g200 mm).