Alkaloid profiling of the Chinese herbal medicine Fuzi by combination of matrix-assisted laser desorption ionization mass spectrometry with liquid chromatography-mass spectrometry

Abstract

A matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) method was developed for the high throughput and robust qualitative profiling of alkaloids in Fuzi--the processed lateral roots of the Chinese herbal medicine Aconitum carmichaeli Debx (A. carmichaeli). After optimization, powdered roots--without any further sample preparation--could be used to screen for the presence of Aconitum alkaloids. Furthermore, the semi-quantitative potential of MALDI-MS was confirmed using liquid chromatography-mass spectrometry (LC-MS) as reference. In total over sixty alkaloids were detected by LC-MS and fifteen of them were tentatively identified. Both MALDI-MS and LC-MS analysis revealed significant variation in alkaloid content in different (commercial) samples. LC-MS analysis of three toxic alkaloids in 14 batches of Fuzi resulted in a variation of their concentrations expressed as RSDs of 138%, 99% and 221% for aconitine, hypaconitine and mesaconitine, respectively. The variation in concentrations (expressed as RSD) of about the ninety constituents detected were classified as follows: 13 constituents showed an RSD of 77-100%, 46 with an RSD of 100-150%, 21 with an RSD of 150-200% and 9 constituents with an RSD in concentration of 200-235%. These results demonstrate a strong difference in chemical composition of the various Fuzi and illustrate the necessity of adequate QA/QC procedures for both safety and efficiency of herbal medicine. The described analytical procedures for alkaloid profiling could play a role in these procedures.