Structural characterization of flavonoid C ‐ and O ‐glycosides in an extract of Adhatoda vasica leaves by liquid chromatography with quadrupole time‐of‐flight mass spectrometry

Rationale Adhatoda vasica Nees is a well‐known Ayurvedic medicinal plant, belonging to the family Acanthaceae. This study aims to seek identification and characterization of flavonoid C ‐ and O ‐glycosides in the aqueous fraction of the plant leaves. Methods A method was developed for simultaneous characterization of flavonoids and their glycosides using high‐pressure liquid chromatography with quadrupole time‐of‐flight mass spectrometry (HPLC/ESI‐QTOF‐MS/MS). The chromatographic separation was carried on an Agilent Poroshell 120 EC‐C 18 column (4.6 × 150 mm, 2.7 µm) operated with 0.1% formic acid aqueous solution and methanol as the mobile phase. Results The fragmentations of the studied [M–H] − ions of C ‐glycosides were shown to be cross‐ring cleavages of the glycoside moiety [M–H–(60/90/120)] − whereas O ‐glycosides were shown to eliminate the sugar moiety (Y 0 − or [Y 0 –H] − ) from the aglycone unit; 6‐ C ‐glycosides exhibited [M–H–18] − , a characteristic ion, and also a higher abundance of 0,3 X 6 or 8 ions in comparison to 8‐ C glycosides; flavonoid 6,8‐di‐ C ‐glycosides exhibited cross‐ring cleavages of the sugar attached to the C‐6 position preferentially. Conclusions This method was successfully applied for analysis of flavonoids and their glycosides in Adhatoda vasica leaves. A total of 29 compounds were tentatively identified including 17 C ‐, nine O ‐glycosides and three flavonoids. Copyright © 2015 John Wiley & Sons, Ltd.