Fast determination of saikosaponins in Bupleurum by rapid resolution liquid chromatography with evaporative light scattering detection

Abstract

A rapid resolution liquid chromatography coupled with evaporative light scattering detection method was established for simultaneous determination of six saikosaponins, namely saikosaponin a, saikosaponin c, saikosaponin d, 6''-O-acetylsaikosaponin a, 3''-O-acetylsaikosaponin d and 6''-O-acetylsaikosaponin d in Bupleurum. The analysis was performed by using an Agilent Zorbax SB-C18 column (1.8 microm, 3.0 mm x 50 mm i.d.) at gradient elution of water and acetonitrile, and the saikosaponins were well separated within 12 min, which provided about a fourfold reduction in analysis time by comparing a conventional high performance liquid chromatography method. Owing to their low ultraviolet absorption, the saikosaponins were detected by evaporative light scattering. The standard curves to quantify the saikosaponins were constructed by the log-log plot, which showed good linearity with the correlation coefficients exceeding 0.9954. The detection limits and quantification limits ranged in 8.38-25.00 microg/mL and 25.13-45.00 microg/mL, respectively. Satisfactory intra-day and inter-day precisions were achieved with the relative standard deviation (R.S.D.) less than 6.58%, and the average recoveries obtained were in the range of 96.9-100.4%. In addition, MeOH-1.0% (v/v) pyridine was found to be the best the extraction solvent when compared to MeOH and MeOH-1.0% (v/v) ammonia water. A total of 23 samples of roots of Bupleurum from different species or locations were examined with this analytical method, and their chemical profiles provided information for the chemotaxonomic investigation. The results demonstrated that the analytical method is highly effective for the quality evaluation of Bupleurum species.