Flavonoids from Ledeb. and their cytotoxic activities against human cancer cell lines.

Flavonoids have been demonstrated to have cytotoxic activities toward numerous human cancer cells, whereas they have little or no effect on normal cells. The numerous flavonoids in traditional Chinese herbs may be promising candidates for the development of novel anti-cancer drugs. Our previous study demonstrated that CHCl and 95% ethanol eluate (EE) fractions have the strongest cytotoxic activities against human cancer cell lines of the 9 fractions separated from Ledeb., which is widely used to prevent and treat diverse diseases in Northeast China. In the present study, 8 flavonoids were isolated from the 95% EE fraction of Ledeb. The chemical structures of the compounds were elucidated by extensive spectroscopic analyses. The following 5 flavonoids were isolated for the first time from this plant: Jaceosidin, kaempferol, quercetin, luteolin and quercitrin. A total of 2 flavonoids from the CHCl fraction and 8 flavonoids from the 95% EE fraction were examined to evaluate their cytotoxic activities against human SK-HEP-1 hepatoma cancer cells and human HeLa cervical cancer cells, respectively. The results revealed that 2 flavonoids had marked cytotoxic activities against HeLa cells.