Selective cytotoxicity, inhibition of cell cycle progression, and induction of apoptosis in human breast cancer cells by sesquiterpenoids from Inula lineariifolia Turcz.

Four new sesquiterpenoid dimers (lineariifolianoids E-H, 1-4), five new sesquiterpenoids (5-9), and seven known sesquiterpenoids (10-16) were isolated from the aerial parts of Inula lineariifolia Turcz. Their structures were determined by spectroscopic data analysis and X-ray diffraction studies. The compounds were then evaluated for their in vitro cytotoxicity against two human breast cancer cell lines (MCF-7 and MDA-MB-231) and one normal breast cell line (MCF-10A). Lineariifolianoid E (1) showed IC50 values of 1.56 µM and 2.75 µM against MCF-7 and MDA-MB-231, respectively. However, lineariifolianoid E demonstrated low toxicity to MCF-10A cells, which indicated a selective cytotoxicity for tumor cells. Further studies also presented that lineariifolianoid E had significant, dose-dependent effects on cell cycle progression and apoptosis in breast cancer cells.