Determination of iridoid glycosides by micellar electrokinetic capillary chromatography-mass spectrometry with use of the partial filling technique

A fast and easy method was sought for determination of the iridoid glycosid es catalpol, ketologanin, verbenalin, loganin, 8-epi-loganic acid, geniposi dic acid and 10-cinnamoyl catalpol in plant samples. The method involved mi cellar electrokinetic capillary chromatography (MEKC) coupled on-line to ma ss spectrometry. The partial filling technique and electrospray ionization were used. Seven iridoid glycosides could be separated with use of MEKC und er basic conditions. However, 8-epi-loganic acid and geniposidic acid could not be detected simultaneously with the five neutral iridoid glycosides by mass spectrometry. Therefore, only the neutral iridoid glycosides were scr eened from plant samples. Catalpol, verbenalin, loganin and possibly 10-cin namoyl catalpol were found in an examination of seven plant species in the genera Plantago, Veronica, Melampyrum, Succisa, and Valeriana. Aucubin, whi ch was not included in the sample mixture used in method development becaus e of overlapping with catalpol in MEKC, was also detected. The limits of de tection for the iridoid glycosides, both at the UV and at the mass spectrom eter, are given.