Determination of free isomeric oleanolic acid and ursolic acid in Pterocephalus hookeri by capillary zone electrophoresis

A rapid capillary zone electophoresis (CZE) method for the quantification of two bioactive terpenes in Pterocephalus hookeri was developed. With β-cyclodextrin as an additive, excellent resolution for these hydrophobic isomers can be obtained in less than 11 min. Linear calibration range for oleanolic acid was between 15.6 and 1000 μg/ml (r = 0.9998), for ursolic acid between 31.2 and 1000 μg/ml (r = 0.9992). The limits of detection for oleanolic acid and ursolic acid were 3.4 and 3.8 μg/ml, respectively. The contents of the free oleanolic acid and ursolic acid in P. hookeri were determined with recoveries ranging from 95.2 to 106.0%. The contents of oleanolic and ursolic acids were found to be 0.21 mg/g (RSD 5.49%) and 0.53 mg/g (RSD 3.37%), respectively. After hydrolysis by acid, these values were 1.12 mg/g (RSD 3.29%) and 0.43 mg/g (RSD 3.42%).