Global identification strategy based on mass spectrometry for studying protostane triterpenoids in rhizomes of Alisma orientalis

Abstract

The liquid chromatography hybrid ion trap time-of-flight mass spectrometry (LCMS-IT-TOF) combined with a global identification strategy was applied to studying the protostane triterpenoids (PTs) in the rhizomes of Alisma orientalis in this paper. Initially, the MSn analyses of four reference compounds were performed to summarize the fragmentation rules of PTs. Subsequently, a series of ions of PTs were presented by LC–MSn analyses of the crude extract of alismatis rhizome, from which six ions at m/z 339, 353, 365, 381, 383 and 397 with high frequency of occurrence were selected as diagnostic ions to classify the peaks. Twenty peaks were classified into six families based on common ions. A network was established for the six families via diagnostic ions. 20 PTs including 1 new compound and 19 known ones were characterized through such strategy, fragmentation rules and references. Ultimately, the detected new compound and two known compounds were isolated from the total extract of A. orientalis under the guide of above method, of which the new compound was identified as 11-deoxylalisol F by MS and NMR spectrum. This systematical investigation on the PTs demonstrated that such a strategy could be widely used in the analysis and separation of natural products.