New liquid chromatography: Mass spectrometry assay for natural phytoestrogens from vegetable extracts

A new liquid chromatography tandem mass spectrometry (LC-MS/MS) assay for the quantification of seven isoflavones (daidzin, genistin, ononin, daidzein, glycitein, genistein, and formononetin) and coumestrol in vegetable extracts was developed. The separation was performed on a Zorbax SB-C18 column with a mixture of methanol (solvent A) and 0.1% (v/v) acetic acid in water (solvent B) under gradient conditions at 50 degree C with a flow rate of 1 mL min super(-1). The detection of analytes was performed by electrospray ionization, negative ionisation, in non-reactive MS super(2) mode for aglycons or in reactive MS super(2) mode for glycosides. The method shows a good linearity (r super(2) > 0.9948) over the concentration range of 40-4000 ng mL super(-1) for all analytes, a good precision (CV