Isolation and structural elucidation of indole alkaloids from Geissospermum vellosii by mass spectrometry

Alkaloids from the stem bark of Geissospermum vellosii possess a variety of therapeutic properties including antimalarial activities, activity as a sexual stimulant and inhibition of the proliferation of HIV and herpes viruses. Methods currently used to isolate the active components from G. vellosii are time-consuming, labor intensive, and result in low recovery. In addition, there is a lack of sensitive and accurate analytical methods for the structural characterization and identification of alkaloid components in minor quantities. A combination of high performance counter-current chromatography and ESI tandem mass spectrometry (MSn) was established to isolate alkaloids from the stem bark of G. vellosii, and study their electrospray ionization mass spectrometry fragmentation behavior. Five indole alkaloids were successfully isolated and identified by nuclear magnetic resonance and mass spectrometry. The multi-stage tandem mass spectrometric data were used to study their fragmentation pattern and set a model for detailed structure characterization of related indole alkaloids. The presence of the even mass fragment ion suggestive of an odd number of nitrogen at m/z 144 corresponding to C10H9N was characteristic to indole alkaloids. The results of the experiments demonstrated that the combination of high performance counter current chromatography and ESI-MSn is a sensitive, selective and effective approach for rapid isolation and characterization of alkaloids from G. vellosii.

► Isolation of indole alkaloids from the stem bark of Geissospermum vellosii using high performance counter-current chromatography.
► Identification of indole alkaloids by nuclear magnetic resonance and mass spectrometry.
► Structural characterization of indole alkaloids by electrospray ionization tandem mass spectrometry.
► Establishment of mass spectrometry fragmentation pattern of indole alkaloids.