Dereplication-guided isolation of novel hepatoprotective triterpenoid saponins from Celosiae Semen by high-performance liquid chromatography coupled with electrospray ionization tandem quadrupole-time-of-flight mass spectrometry.

Although natural products (NPs) from ethnomedical plants have played a vital role in modern drug discovery, separation and purification of bioactive compounds from plant extract is still challenging. In this study, a dereplication strategy using HPLC-QTOF-MS was employed to rapidly discover and highly targeted isolate the novel hepatoprotective triterpenoid saponins from the methanol extract of Celosiae Semen. Firstly, four known saponins, i.e. celosin H, celosin I, celosin J, and pseudoginsenoside RT1 were selected as model compounds, and their fragmentation patterns in ESI-QTOF-MS/MS were characterized. Secondly, an HPLC-QTOF-MS/MS method was applied to chemically screen the saponins of interest, and thereby to guide the subsequent fraction and isolation procedure. Thirdly, the targeted isolation of desired compounds afforded two new triterpenoid saponins namely celosin K (1) and celosin L (2), which were structurally elucidated by combination of extensive NMR spectroscopic and chemical analyses. Finally, the protective effects of compounds 1 and 2 against APAP-induced hepatotoxicity in HepG2 cells were evaluated. These results indicate that the HPLC-QTOF-MS-guided isolation is an efficient methodology for isolating new NPs from medicinal plants through improving selectivity in separation and purification process.