Enhanced analysis of triterpenes, flavonoids and phenolic compounds in Prunella vulgaris L. by capillary zone electrophoresis with the addition of running buffer modifiers

A cyclodextrin-modified capillary zone electrophoresis method was developed for the separation and determination of three isomeric compounds (ursolic acid, oleanolic acid and betulinic acid), caffeic acid, p-coumaric acid, rosmarinic acid, rutin and quercetin. Without the addition of beta-cyclodextrin (beta-CD) and methanol, the separation of these analytes was poorly resolved. These eight compounds, however, were well separated from each other within 20 min with a borax running buffer (40 mM of borax, pH 9.4) containing 2mM beta-CD and 4% (v/v) methanol at the voltage of 25kV, temperature of 25 degrees C and detection wavelength of 210 nm. The relative standard deviations (RSDs) of migration time ranged from 0.16 to 0.74% while those of the peak area ratios ranged from 2.17 to 4.61% for six determinations of the analytes at concentration of 10 and 25 mu g mL(-1). The correlation coefficients of the calibration curves of the analytes were all > 0.998, and the recoveries were from 96.8 to 103.6%. The method was successfully applied to determine these bioactive components in the samples of Prunella vulgaris L and its beverage drink products. Our results reveal that only the isomeric compounds and rosmarinic acid could be detected in the spikes of P vulgaris L; other components were either too low to be detected or not present while only rosmarinic acid was detected in the beverage products. (c) 2008 Elsevier B.V. All rights reserved.