HPLC analysis of liquorice triterpenoids--applications to the quality control of pharmaceuticals.

A reversed-phase HPLC method is proposed for the separation of five liquorice triterpenoids, 18 beta glycyrrhetic acid (beta GA), 18 alpha glycyrrhetic acid (alpha GA), 24-hydroxy-18 beta-glycyrrhetic acid (24-OH-beta GA), alpha and beta liquiritic acid (alpha and beta LA), with potentially different biological activities. The method has been developed by studying the influence of the type of stationary phase, pH, amine modifier and organic modifier on the resolution of the five compounds. The optimized chromatographic conditions were then successfully applied to the analysis of alpha- and beta-GA in pharmaceutical preparations (toothpaste and creams) on a reversed-phase Phenomenex Ultracarb 5 ODS (30) column (150 x 4.6 mm i.d.), using as the mobile phase acetonitrile-THF-0.010 M dioctylammonium phosphate buffer (pH 6.5) (25:20:55, v/v/v) at a flow-rate of 0.8 ml min-1. SPE methods with diolic and C18 sorbents were developed to isolate and concentrate the analytes and to enhance the sensitivity for the determination of alpha-GA as an impurity in the beta-GA preparations. The method was found to be reliable and suitable for the quality control of beta-GA preparations.