PREPARATIVE SEPARATION OF IRIDOID GLYCOSIDES FROM EUCOMMIA ULMOIDES OLIV.BY REVERSED-PHASE HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

摘要

The separation of three iridoid glycosides, aucubin, geniposide and geniposidic acid, from the traditional Chinese medicinal herb Eucommia was investigated by RP-HPLC on a C_(18) reversed-phase preparative column. The relationship between the retention time of these iridoid glycosides and their structure was discussed. In order to obtain simultaneously iridoid glycosides in pure form, greater than 95% pure, some particular steps were taken. The first step was to adjust the mobile phase composition, choosing the elution mode, the column temperature and the flow rate in order to increase the separation factor between the desired components. Next, it was possible to increase the column efficiency and to reduce the time of separation required. Finally the locations of the cut points for the collection of target compounds were chosen carefully to ensure the purities of products. The optimum parameters for simultaneous preparation of iridoid glycosides were obtained by stepwise gradient mode at the wavelength 220 nm because all of the three compounds could be detected at this wavelength with good sensitivity. The suitable mobile phases were consisted of water-ethanol (80:20, v/v, adjusting pH to 2.8 with formic acid) and water-ethanol (70:30) at the flow rate of 45 ml/min. High purity of GPA (98.8%), GP (99.5%) and AU (95.9%) were obtained with good recovery yields of 90%, 92% and 88%, respectively.