HPLC determination of glycyrrhizin and glycyrrhetic acid in biological fluids, after licorice extract administration to humans and rats.

Simple and sensitive HPLC methods were developed for the determination of glycyrrhyzin (G) and its main metabolite glycyrrhetic acid (GA) in biological samples, in order to investigate the pharmacokinetic behaviour of G after oral administration of licorice extract (LE) or G to humans and rats. The analysis have been carried out by HPLC with UV detector (251 nm), after a careful pretreatment of the samples. These methods are suitable in terms of precision and accuracy for the G and GA determination in plasma and urine of human volunteers and in bile, plasma ad urine of rats.