Eremophilane-type sesquiterpene derivatives from the roots of Ligularia lapathifolia

Six new highly oxygenated eremophilane-type sesquiterpene derivatives (1-6), including a norbisesquiterpene, were isolated from an extract of the roots of Ligularia lapathifolia, and their structures were elucidated by spectroscopic methods. The structure of 1 was confirmed by single-crystal X-ray crystallography. In addition, the cytotoxicity of compounds 1, 2, 3, 5, and 6 was evaluated against selected cancer cell lines, including human stomach carcinoma (MGC-803), human hepatoma (HEP-G2), and murine sarcoma (S-180) cell lines.