Fischerisin A and B, cytotoxic sesquiterpenoid-geranylhydroquinones from Ligularia fischeri

During the course of screening natural sesquiterpenoids for new antitumor agents, two novel compounds, fischerisin A (1) and fischerisin B (2), were isolated from the roots of Ligularia fischeri. Their structures were elucidated by interpretation of their IR, high resolution-mass spectrometry (HR-MS), 1D- and 2D-NMR data. Fischerisin A and B are the first representatives of a novel sesquiterpenoid-geranylhydroquinone hybrid, and both compounds exhibited in vitro cytotoxicity against cultured human oral epidermoid carcinoma (KB) and human breast cancer (MCF-7) cell lines with IC(50) values of 9.7 and 10.2 μM, and 9.8 and 17.8 μM, respectively.