Analysis of iridoid glycosides fromPicrorhiza kurroa by capillary electrophoresis and high performance liquid chromatography-mass spectrometry

Summary

A micellar electrokinetic chromatography (MEKC) method was applied to the analysis of iridoid glycosides ofPicrorhiza kurroa Royle ex Benth. Baseline separation was achieved within 16 min using a fused silica capillary and a borate buffer solution (100 mM, pH 8.60) containing 30 mM SDS and 1% acetonitrile. The applied voltage was 25 kV, the thermostating temperature was kept constant at 30°C. Injection was performed in the pressure mode for 2 s, the detection wavelength was 205 nm. For optimization of the CE method an iridoid-containing fraction of a methanolic extract ofP. kurroa was injected. The impact of the electrolyte composition, the pH value, the ionic strength, the concentration of SDS, the influence of organic additives, the voltage and the temperature on resolution of adjacent peaks was studied. The optimized method was used for quantitative determination of the main iridoids in crude methanolic extracts ofP. kurroa.

Analysis was also performed by HPLC-MS using an electrospray ionization (ESI) interface. Conditions were optimized both for efficient HPLC and for the MS system. Mass spectra of all HPLC peaks showed one dominant signal corresponding to [M+Na]⁺. The good agreement of quantitative CE results with those obtained by LC clearly demonstrated the applicability of the presented methods.