Bakkenolides from Petasites tatewakianus.

A new bakkenolide and a known one were isolated from Petasites tatewakianus. The structure of the new compound was elucidated on the basis of spectroscopic methods including IR, EIMS, HRESIMS, 1D and 2D NMR, and the known compound was established by single crystal X-ray structural analysis. The in vitro cytotoxic activity of these two compounds against cultured human cervical carcinoma (HeLa), human breast cancer (MCF-7) and murine Lewis lung carcinoma (LLC) cell lines was also evaluated.