Qualitative and quantitative analysis of flavonoids in the leaves of Isatis indigatica Fort. by ultra-performance liquid chromatography with PDA and electrospray ionization tandem mass spectrometry detection.

A novel method based on ultra-performance liquid chromatography with photo diode array and electrospray ionization tandem mass spectrometry detection (UPLC-PDA-ESI-MS/MS) was developed for the qualitative and quantitative analysis of flavonoids in the leaves of Isatis indigotica Fort. (Daqingye). The separation was carried out on an Acquity UPLC BEH C(18) column with 0.1% formic acid and methanol as the mobile phase under gradient conditions. Eight flavone C-glucosides were identified and their mass spectrometric fragmentation patterns were studied. Among them, the fragmentation pathways of three flavone 6-C-diglucosides with the rare 1-->3 interglycosidic linkage were investigated for the first time. In addition, a quantitative analytical method for six flavone C-glucosides in Daqingye by UPLC-ESI-MS/MS was established and applied for the determination of commercial Daqingye samples from different resources.