Simultaneous Identification of Soyasaponins and Isoflavones and Quantification of Soyasaponin Bb in Soy Products, Using Liquid Chromatography/Electrospray Ionization-Mass Spectrometry

A method has been developed for simultaneous identification of soyasaponins and soy isoflavones in soy products, based on liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS). Soy-based nutraceutical products were analyzed by LC/ESI-MS with detection of protonated and sodiated molecular ions, as well as characteristic fragment ions for these compounds. Soy isoflavones were characterized by a strong protonated molecular ion in addition to corresponding [aglycone + H]+ ions. Monitoring the soyasaponin-specific protonated aglycone and dehydrated aglycone ions throughout the chromatogram provided a unique fingerprint for soyasaponin content in the samples. This mass spectrometric fingerprint also allowed immediate classification of the soyasaponin analytes as group A or B soyasaponins, based on the unique masses of aglycone ions observed for each class. Quantification of soyasaponin Bb in soy-derived materials, based on the use of a purified soyasaponin Bb standard and a glycyrrhizin internal standard, has been accomplished. Keywords: Bioactive; diet; Glycine max; isoflavones; natural product; nutrition; saponins