Abstract: Soyasaponins of three fractions(SS-Ⅰ、SS-Ⅱ、SS-Ⅲ) were obtained by D101A macroporous resin column chromatographic method. SS-Ⅲ were determined by high performance liquid chromatography-negative electrospray ionization tandem mass spectrometry(HPLC-ESI-/MS2).In the method, on line HPLC-ESI-/MS allowed to obtain rapidly useful information about the molecular weight while HPLC-ESI-/MS2 offered the abundant fragment ion peak. So four known group B soyasaponins and one group E soyasaponin were determined respectively. One new composition that had not been reported in soyasaponins before was identified.

Key words: soyasaponins, high performance liquid chromatography-negative electrospray ionization tandem mass spectrometry, group B soyasaponin, group E soyasaponin