Isolation of a new saponin and cytotoxic effect of saponins from the root of Platycodon grandiflorum on human tumor cell lines

A novel triterpenoid saponin, deapioplatycoside E (1) was isolated from the root extract of Platycodon grandiflorum, together with the seven known saponins 2 - 8, i. e., platycoside E (2), deapioplatycodin D3 (3), platycodin D3 (4), polygalacin D2 (5), platycodin D2 (6), deapioplatycodin D (7) and platycodin D (8). The structure of the new saponin 1 was determined on the basis of spectral analysis and chemical evidence. The crude saponin fraction (ED50: ca. 10 - 15 microg/mL) and compounds 6 - 8 (ED50: ca. 4 - 18 microg/mL) exhibited significant inhibition on the proliferation of five kinds of cultured human tumor cell lines, i. e., A549 (non-small cell lung), SK-OV-3 (ovary), SK-MEL-2 (melanoma), XF498 (central nerve system) and HCT-15 (colon), in vitro.