Simultaneous Analysis of a Mixture of Iridoids in Water Extracts of Plantago asiatica L. by LC

A simple liquid chromatographic method using an ultraviolet detector was developed for the simultaneous quantification of a mixture of iridoid glycosides, catalpol, aucubin, and geniposidic acid. By adding a minute amount of trifluoroacetic acid into the conventional aqueous acetonitrile mobile phase, the unstable resolution arising from the tautomeric rearrangements in the carboxylic group at the 11 position of geniposidic acid could be solved, resulting in a clear separation profile of the catalpol, aucubin, and geniposidic acid peaks. We were able to quantify the contents of catalpol, aucubin, and geniposidic acid contained in the leaves and seeds of P. asiatica.