CHARACTERIZATION OF C-GLYCOSYLFLAVONES FROM DISSOTIS-ROTUNDIFOLIA BY LIQUID-CHROMATOGRAPHY - UV DIODE-ARRAY DETECTION - TANDEM MASS-SPECTROMETRY

By high-performance liquid chromatography (HPLC) coupled with UV diode -array detection (DAD) and thermospray mass spectrometry (TSP-MS), fou r main constituents of a polar, whole plant extract from Dissotis rotu ndifolia T. were characterized. The four C-glycosylflavones, isoorient in, orientin, vitexin and isovitexin were detected in the methanolic a nd hydroalcoholic extract of the plant as well as in the commercial dr ug preparation 'Sirop de Dissotis'. Although the UV data and TSP mass spectra allowed rapid characterisation of all four C-glycosylflavones, exact attribution of the peaks to their structures could not be achie ved as neither the UV spectra nor the TSP mass spectra enabled differe ntiation of one position isomer from the other. Therefore a successful attempt was made to distinguish the 6-C from the 8-C-glycosylflavones by thermospray tandem mass spectrometry (TSP-MS-MS). The collision in duced dissociation (CID) spectra of the particular ion [M+H-120](+) ga ve fragments which permitted differentiation of position isomers. To c onfirm the accuracy of on-line results, reference compounds were inclu ded in the HPLC study.