Separation of triterpenoid saponins from the root of Bupleurum falcatum by counter current chromatography: The relationship between the partition coefficients and solvent system composition

A separation method using counter current chromatography coupled with an evaporative light-scattering detection system was developed to purify five triterpenoid saponins from the roots of Bupleurum falcatum. The methanol extract was loaded onto a Diaion ® HP20 column and fractionated by a methanol and water gradient elution. The saikosaponin-enriched fraction was obtained by elution with 100% methanol. The two-phase solvent systems used for separation were composed of chloroform/methanol/isopropanol/water at a volume ratio of 60:60:1:60 and 6:6:1:6. The relationship between the isopropanol ratio of each phase and the partition coefficients of the target compounds was investigated by calculating partition coefficient by high-performance liquid chromatography and measuring the accurate composition of each phase by ¹H NMR spectroscopy. Each fraction obtained was collected and dried, which yielded the following five saikosaponins from 700 mg of injected sample: saikosaponin B₁ (8.7 mg), saikosaponin A (86 mg), saikosaponin B₃ (17 mg), saikosaponin B₂ (41 mg), and saikosaponin C (33 mg). Saikosaponin A showed the most potent cytotoxicity against human cancer cells (gastric cancer, AGS cells; breast cancer, MCF-7 cells; and hepatoma, HepG2 cells) after 24 h. The IC₅₀ values for the above three cell types were 34.6, 33.3, and 23.4 μmol/L, respectively.