Quantitative analysis of iridoids, secoiridoids, xanthones and xanthone glycosides in Gentiana lutea L. roots by RP-HPLC and LC–MS

The here described HPLC-method enables the determination of all major, currently known bioactive compounds in gentian roots. A separation of iridoids (loganic acid), secoiridoids (swertiamarin, gentiopicroside, amarogentin, sweroside), xanthones (gentisin, isogentisin) and two xanthone glycosides (gentiosides) was possible on RP-18 column material, using 0.025% aqueous TFA, acetonitrile and n-propanol as mobile phase. The method is sensitive (LOD ≤ 37 ng/ml and LOQ ≤ 112 ng/ml), accurate (recovery rates of spiked samples were between 96.7 and 101.5%), repeatable (σrel ≤ 1.7%) and precise (intra-day variation ≤ 4.6%, inter-day variation ≤ 3.1%). LC–MS experiments performed in negative ESI mode assured peak purity and identity. Analysis of several commercially available G. lutea samples showed that gentiopicroside is the most dominant compound in the specimens (4.46–9.53%), followed by loganic acid (0.10–0.76%), swertiamarin (0.21–0.45%) and the xanthone glycosides. Gentisin and isogentisin were found in much lower concentrations between 0.02 and 0.11%, respectively.