Quality control and identification of steroid saponins in crudeextracts from Dioscorea zingiberensis C. H. Wright byfingerprint with HPLC-ELSD and HPLC-ESI-Quadrupole/Time-of-fight tandem massspectrometry

摘要

In this study, a fingerprint of steroid saponins, the major bioactive constituents in the crude extracts from Dioscorea zingiberensis C. H. Wright (DZW), has been established for the first time by high-performance liquid chromatography coupled with evaporative light scattering detector (HPLC-ELSD) and the simultaneous characterization of the steroid saponins by high-performance liquid chromatography coupled with electrospray ionization-mass spectrometry and quadrupole tandem time-of-fight mass analyzers detection (HPLC-ESI-Q/TOF). These HPLC analyses were both carried out on a Welchrom C18 column (250 mm × 4.6 mm I.D., 5 μm) with a mobile phase composed of water and acetonitrile under gradient elution. There were 68 common characteristic peaks in the fingerprints, in which 12 of them were confirmed by comparing their mass spectra and retention times with those of the reference compounds. In order to identify the other unknown peaks, their fragmentation behaviors characteristic for the major groups of steroid saponins from DZW with six types of aglycone skeletons were discussed in detail, and possible MS/MS fragmentation pathways were proposed for aiding the structural identification of these components. According to the summarized fragmentationpatterns, these peaks were tentatively assigned by matching their empiricalmolecular formula with those of the published compounds, or by elucidating theirquasi-molecular ions and fragment ions referring to available literatureinformation when the reference standards were unavailable. As a result, 22steroid saponins were found in DZW for the first time. In addition, thequantitative analysis of the 12 known peaks was accomplished at the same timewhich indicated that there was a great variability in the amount of these activecompounds in different batches in the crude extracts. This approach coulddemonstrate that the fingerprint could be considered to be a suitable tool tocomprehensively improve the quality control of DZW, and the identification andstructural elucidation of the peaks in the fingerprint may provide importantexperimental data for further pharmacological and clinical researches.