Rapid separation and characterization of active flavonolignans of Silybum marianum by ultra-performance liquid chromatography coupled with electrospray tandem mass spectrometry

Ultra-performance liquid chromatography (UPLC) interfaced with the electrospray ionization (ESI) tandem mass spectrometer (MSn) was developed for the simultaneous determination of silychristins A (1) and B (2), silydianin (3), silybins A (4) and B (5), and isosilybins A (6) and B (7), major bioactive flavonolignans in silymarin, a herbal remedy derived from the milk thistle Silybum marianum. In this study, the seven major active flavonolignans including the diastereomers 1/2, 4/5, and 6/7 were completely separated using UPLC with an ACQUITY UPLC C18 column and a MeOH/water/formic acid mobile phase system. The collision-induced dissociation (CID) MSn spectra of these flavonolignans were studied systematically using ESI-MS. The results with the present methodology show that UPLC–MSn can be useful for general screening of active natural products from plant extracts and for the specific quality control of silymarin.