High-performance liquid chromatography-diode array detection/electrospray ionization mass spectrometry for the simultaneous analysis of cis-, trans- and dihydro-2-glucosyloxycinnamic acid derivatives from Dendrobium medicinal plants

Abstract

Sensitive, selective and reliable high-performance liquid chromatography (HPLC)-diode array detection (DAD)/electrospray ionization multi-stage mass spectrometry (ESI-MSⁿ) methods have been developed for the characterization of nine 2-glucosyloxycinnamic acid derivatives and quantitative analysis of three of the major 2-glucosyloxycinnamic acids, <i>cis</i>-melilotoside, <i>trans</i>-melilotoside and dihydromelilotoside, present in <i>Dendrobium</i> medicinal plants. The identities of the latter three major 2-glucosyloxycinnamic acids were confirmed by comparing their retention times, UV and mass spectra with those of the reference standards. The characteristic ESI-MSⁿ fragmentation patterns of the remaining six 2-glucosyloxycinnamic acid derivatives, which are similar to the three major compounds, have allowed the putative elucidation of their structures. The concentrations of the <i>cis</i>-, <i>trans</i>- and dihydromelilotosides were simultaneously determined by HPLC/ESI-MS² using the multiple reaction monitoring (MRM) mode in extracts of <i>Dendrobium</i> species. The method was validated with respect to the overall intra- and inter-day variation (RSD less than 8%) and the limits of quantification for the <i>cis</i>-, <i>trans</i>- and dihydromelilotosides were 0.09, 0.09 and 0.01 µg/mL, respectively.