Identification and characterization of saponins in extract of Ziziphi spinosae Semen (ZSS) by ultra-performance liquid chromatography-electrospray ionization-quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-QTOF-MSE)

This paper was designed to develop a novel method via ultra-performance liquid chromatography-electrospray ionization-quadrupole time-of-i¬‚ight tandem mass spectrometry (UPLC-ESI-QTOF-MSE) for the analysis and identification of saponins from extract of Ziziphi spinosae Semen (ZSS). The possible fragmentation pathways were proposed on the basis of MSE data. In results, 13 saponins, including two unknown compounds, were identified and they were divided into two groups on the basis of mass spectral analysis. Compound 1~6, which were of keto-dammarane type triterpene saponin, underwent McLafferty-type (or McLafferty) rearrangement, and compound 7~13, which were of dammarane type triterpene saponin, underwent retro Diels-Alder (RDA) cleavage. The results testified that the developed method was useful to rapidly and simultaneously identify the constituents in ZSS. In this paper, the principles of McLafferty-type (or McLafferty) rearrangement were firstly utilized to elucidate the proposed fragmentation pathways of saponins from ZSS.   Key words: Ziziphi spinosae semen, ultra-performance liquid chromatography (UPLC), quadrupole time-of-i¬‚ight tandem mass spectrometry (QTOF-MSE), retro Diels-Alder cleavage, McLafferty-type rearrangement.