Multiple-stage tandem mass spectrometry for structural characterization of saponins.
Nanoelectrospray ion trap multiple-stage tandem mass spectrometry was applied to characterize saponins present in HPLC fractions from Quil A, a commercially available bark extract. An analytical strategy was developed based on recognition of carbohydrate sequence ions as well as glycosidic ring-cross ions formed by gamma-hydrogen rearrangements and successive retro-Diels-Alder fragmentations. These ions could be used for the determination of several glycosidic linkages, ring sizes, and positions of acyl groups. The presence of an acyl group on a monosaccharide residue facilitated the determination of the substitution pattern, due to the induction of ring-cross fragmentation. Deuteriomethylation resulted in a more extended set of ring-cross ions, thus allowing determination of additional glycosidic linkages. An analysis typically consumed 200 ng of sample and a total of 1-4 h for measurement and interpretation. The applied method is attractive as a pre-NMR analysis, especially because it resulted rapidly in an overall idea of the structure even when starting from scratch. The multiple-stage tandem approach enabled structural determination of saponins to a more detailed level than achievable with current single-stage tandem mass spectrometry.
van Setten
D C
DC
Department of Molecular Spectroscopy, National Institute of Public Health, Bilthoven, The Netherlands.
ten Hove
G J
GJ
Wiertz
E J
EJ
Kamerling
J P
JP
van de Werken
G
G
D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D003903:Deuterium; D007477:Ions; D013058:Mass Spectrometry / Q000379:methods*; D008969:Molecular Sequence Data; D009005:Monosaccharides / Q000032:analysis; D062605:Quillaja Saponins; D015203:Reproducibility of Results; D012503:Saponins / Q000032:analysis* / Q000737:chemistry*; D014315:Triterpenes / Q000737:chemistry
D007477:Ions; D009005:Monosaccharides; D062605:Quillaja Saponins; D012503:Saponins; D014315:Triterpenes; C046386:Quil A; D003903:Deuterium