Rapid Identification of Polyphenol C-Glycosides from Swertia franchetiana by HPLC--ESI-MS--MS

High-performance liquid chromatography coupled to positive ion electrospray ionization tandem mass spectrometry (MS) and diode array detection was employed to identify the polyphenol C-glycosides in the extract of Swertia franchetiana, a traditional Chinese/Tibetan herb. The neutral loss scan of the extract of S. franchetiana using the characteristic losses of 120 and 150 u provided a detailed profile of the polyphenol C-glycosides in the complex mixture. On-line UV spectroscopy along with MS-MS and MS-MS-MS mass spectra analysis produced with and without in-source collision induced dissociation was contributed to discriminate and identify the polyphenol C-glycosides. Three xanthone C-glycosides (i.e., mangiferin, isomangiferin, and 1,6,7-trihydroxyl-2-C-glucosexanthone) and three flavone C-glycosides (i.e., isoorientin, isovitexin, and swertisin) were tentatively identified. Isomangiferin and 1,6,7-trihydroxyl-2-C-glucosexanthone were for the first time found in this plant.