Characterisation of soy isoflavones and screening for novel malonyl glycosides using high-performance liquid chromatography-electrospray ionisation-mass spectrometry

HPLC combined with electrospray ionisation (ESI)-MS and photodiode array de tection has been employed to study the isoflavone components of soy. All of the known soy isoflavones separated by HPLC were identified and characteri sed, and three novel isoflavones were detected and screened out. These mino r isoflavones were deduced to be isomers of 6 " -O-malonyl isoflavone glyco sides, based on the ESI-MS and UV data, in which the malonyl group is attac hed at a position other than the 6 " position of the glycosyl moiety of the molecule. These novel malonyl glycosides are as thermally labile as the 6 " -O-malonyl glycosides, being converted into known isoflavone glycosides a fter heating in aqueous ethanol. The advantages of HPLC-ESI-MS in detection of novel isoflavones from plant extracts are reviewed. Copyright (C) 2001 John Wiley & Sons, Ltd.