Chemical assay of glycyrrhizin in medicinal plants by pressurized liquid extraction (PLE) with capillary zone electrophoresis (CZE)



Glycyrrhizin in Radix glycyrrhizae or liquorice was determined using a laboratory made dynamic pressurized liquid extraction (PLE) system coupled with capillary zone electrophoresis (CZE). The amount of glycyrrhizin was determined using CZE with an aqueous buffer of 10 mM of sodium tetraborate at pH 9.25 with UV detection at 254 nm. The effects of pH, buffer concentration, and the applied voltage on the electrophoretic separation were investigated. Temperature was found to be the important parameter in PLE as it was observed that the amount of thermally labile components such as glycyrrhizin extracted from medicinal plants decreased with increasing temperature from 100 to 160°C. The amount of glycyrrhizin extracted by PLE with methanol as solvent for glycyrrhizin in medicinal plants was found to be comparable or higher compared to multiple step ultrasonic extraction using a mixture of methanol/water (70 : 30). The overall method precision was found to vary from 6.9 to 8.1% (RSD) for glycyrrhizin in medicinal plants. The specificity of the method was checked using standard addition experiments.