Screening of tricyclic quinazoline alkaloids in the alkaloidal fraction of Adhatoda beddomei and Adhatoda vasica leaves by by high-performance liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry

Abstract

RATIONALE Adhatoda beddomei and Adhatoda vasica are popular Ayurvedic medicinal plants in India, belonging to family Acanthaceae. Tricyclic quinazoline alkaloids are found to be the most abundant in these plants which are responsible for broad-spectrum medicinal properties. This study aims to seek identification and characterization of those alkaloids based on the fragmentation pattern. METHODS A method was developed to elucidate the main fragmentation pathways of tricyclic quinazoline alkaloids in positive ion mode using high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometer (HPLC-ESI-QTOF-MS/MS). Chromatographic separation was carried on a Supelco Discovery HS C18 column (15 cm×4.6 mm, 3μm) with 0.1% formic acid aqueous solution and acetonitrile, as a mobile phase. RESULTS In full scan mass spectra, protonated molecules were observed for all the quinazoline alkaloids. Ring cleavages of the tricyclic quinazoline moiety were observed in MS2 spectra and the characteristic ions provide valuable structural information of these alkaloids. Fragmentation pathways and fragment ion structures were proposed in two groups of quinazoline alkaloids. CONCLUSIONS The established fragmentation patterns have been successfully used to identify 23 tricyclic quinazoline alkaloids in the alkaloidal fraction of A. beddomei and A. vasica.