Authentic compound-free strategy for simultaneous determination of primary coumarins in Peucedani Radix using offline high performance liquid chromatography–nuclear magnetic resonance spectroscopy–tandem mass spectrometry

Abstract

Herein, a strategy is proposed for the simultaneous determination of primary coumarins in Peucedani Radix (Chinese name: Qianhu). The methodology consists of three consecutive steps: 1) Semi-preparative LC in combination with a home-made automated fraction collection module to fragment the universal metabolome standard into ten fractions (Frs. I–X); 2) LC–accurate MS/MS and quantitative 1H NMR spectroscopy conducted in parallel to acquire the qualitative and quantitative data of each fraction; 3) Robust identification and quantification of components by use of LC coupled to multiple reaction monitoring. In this final step, the most significant fractions (Frs. III–X) were pooled to serve as the pseudo-mixed standard solution. Meticulous online parameter optimization was performed to obtain the optimal parameters, including ion transitions and collision energies. Concerns were particularly paid onto pursuing the parameters being capable of monitoring regio-specific isomers, notably praeruptorin E vs. 3′-isovaleryl-4′-angeloylkhellactone. The quantitative performance of the method was validated according to diverse assays. Eleven primary coumarins (1–11) were unambiguously identified and absolutely quantified, even though no external reference compound was used. Above all, the integrated strategy not only provides a feasible pipeline for the quality assessment of Peucedani Radix, but more importantly, shows the potential for authentic compound-free quantitative evaluation of traditional Chinese medicines. KEY WORDS: Authentic compound-independent quantitation, Offline LC–NMR–MS/MS, Automated fraction collection module, Quantitative 1H NMR, Peucedani Radix, Regio-specific monitoring