Comprehensive chemical analysis of Venenum Bufonis by using liquid chromatography/electrospray ionization tandem mass spectrometry

A rapid, sensitive and versatile liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method was developed for the comprehensive analyses of the chemical constituents contained in the Chinese medicine-Venenum Bufonis (VB, Chan' Su in Chinese). LC analysis was carried out on an Agilent Eclipse plus C18 RRHD column (2.1 × 150 mm, 1.8 μm) with a linear gradient solvent system of water (0.1% formic acid) and acetonitrile (0.1% formic acid) as mobile phase. Detection and quantification were performed by multiple reaction monitoring (MRM) transitions via electrospray ionization (ESI) source operating in the positive ionization mode. Through "Molecular Feature Extraction" (MFE), more than 900 features were detected from VB extracts. Among them, a total of 97 components were identified using the Agilent METLIN accurate mass matching database (DB) established according to those reported in the literatures. Further more, 30 high quality matches were obtained by comparisons of their accurate mass and retention times (AMRT) with those imported out in the developed personal database (METLIN DB with AMRT). The characteristic fragmentation pathways were proposed for the tentative characterization of four representative types of bufadienolides in the present work. The targeted MS/MS experiment of the 30 major compounds was performed for their quantification and semi-quantification. And 7 of them were quantified over the assaying concentration range of 5.0–500 pg/μL. The lowest limit of detection and quantification of them were 0.25–0.50 and 1.25–0.25 pg/μL, respectively. The recoveries varied from 83 to 106% depending on the chemical types and different extraction solvents. The remained 23 bufosteroids were simultaneously semi-quantified using three representative standard compounds as their standard references, respectively.