title: Multiple-stage tandem mass spectrometry for differentiation of isomeric saponins.
abstract: Four isomers of steroidal saponins were differentiated using multiple-stage tandem mass spectrometry combined with electrospray ionization (ESI-MS(n)). With the addition of lithium salt, the [M+Li](+) ions of saponins were observed in the ESI spectra. MS(n) spectra of these [M+Li](+) ions provided detailed structural information and allowed differentiation of the four isomeric saponins. The cross-ring cleavage ions from the saccharide chains of the saponins could be used as diagnostic ions for information concerning the linkage of the sugar moieties of the saponins. The masses of the X, A, Y and C type fragment ions formed from [M+Li](+) ions of the isomeric saponins provided information defining the methyl group locations.
authors.affiliation: Laboratory of New Drug Research and Mass Spectrometry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China.
authors.forename: Fengrui
authors.initials: F
authors.lastname: Song
authors.forename: Meng
authors.initials: M
authors.lastname: Cui
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Liu
authors.forename: Biao
authors.initials: B
authors.lastname: Yu
authors.forename: Shuying
authors.initials: S
authors.lastname: Liu
mesh_terms: D001665:Binding Sites; D045424:Complex Mixtures / Q000032:analysis / Q000737:chemistry; D006027:Glycosides / Q000032:analysis / Q000737:chemistry; D007536:Isomerism; D018021:Lithium Chloride / Q000737:chemistry*; D012503:Saponins / Q000032:analysis* / Q000737:chemistry* / Q000145:classification; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D045424:Complex Mixtures; D006027:Glycosides; D012503:Saponins; D018021:Lithium Chloride