LIQUID-CHROMATOGRAPHIC THERMOSPRAY MASS-SPECTROMETRIC ANALYSIS OF CRUDE PLANT-EXTRACTS CONTAINING PHENOLIC AND TERPENE GLYCOSIDES

In crude plant extracts, constituents of biological or pharmaceutical interest often exist in the form of glycosides. Mass spectral investigations of these metabolites require soft ionization techniques such as desorption chemical ionization (D/CI) or fast atom bombardment if information on molecular mass or sugar sequence is desired. Thermospray (TSP) provides mass spectra similar to those obtained with positive-ion D/CI-MS using NH3 and thus is potentially applicable to on-line analyses for these compounds and can be applied to plant extract analysis. Extracts of Gentianaceae species (containing secoiridoids and xanthone mono- and diglycosides), Polygalaceae (containing flavonol di- and triglycosides), Pedaliaceae (containing iridoids, phenylpropanoid glycosides) and Leguminosae (containing triterpene glycosides) have been screened by LC-TSP-MS. The plant extracts were analysed under standard LC-TSP-MS conditions on reversed-phase columns using methanol-water or acetonitrile-water gradients. Good optimization of the temperature of the source and the vaporizer was crucial for the observation of pseudo-molecular ions of glycosides.