Qualitative analysis and enantiospecific determination of angular-type pyranocoumarins in Peucedani Radix using achiral and chiral liquid chromatography coupled with tandem mass spectrometry

Abstract

Angular-type pyranocoumarins (APs), the derivatives of khellactone, are widely documented as the main active constituents in Peucedani Radix (Chinese name: Qian-hu). Owing to the natural occurrence of chiral centers, enantiomers of APs are extensively distributed in the original plant, and enantioselective performances have been definitely demonstrated for these enantiomers. In current study, the chemical characterization of the major and minor APs in Peucedani Radix was performed using ultra high performance liquid chromatography coupled with diode array detector and hybrid ion trap-orbitrap mass spectrometry. On the other hand, a heart-cut two-dimensional achiral–chiral liquid chromatography combining triple quadropole-linear ion trap mass spectrometry system (2D LC–MS/MS) was developed for simultaneous enantiospecific quantification of eighteen coumarins, including seven pairs of enantiomers. Eleven APs (1–11) were recruited to propose UV absorption characteristics and electrospray ionization fragmentation patterns of APs. A total of 42 components were categorized into APs based on their UV spectral properties and identified according to the proposed mass fragmentation pathways, while two linear-type furanocoumarins (12–13) were unambiguously assigned by further purification. A Capcell core RP-C18 column was employed in the primary LC dimension to achieve efficient racemic separation for the main chemical constituents (1–9 and 12–13) in Peucedani Radix, while a Chiralpak AD-RH column was utilized in the secondary dimension to contribute enantioselective separation for seven enantiomerically enriched components (1, 3 and 5–9). Collectively, the results provided the chemical evidences for revealing the material basis of the therapeutic effects of Peucedani Radix, and the developed 2D LC–MS/MS system in the present study is expected to be an ideal tool for the quality control of Peucedani Radix as well as a reliable technique for complex matrices containing both achiral and chiral components.