Determination of 18α-glycyrrhizin and 18β-glycyrrhizin in dog plasma by high-performance liquid chromatography

A high-performance liquid chromatographic method has been developed for the separation and determination of 18α-glycyrrhizin (α-GZ) and 18β-glycyrrhizin (β-GZ) in dog plasma. The two compounds were separated on a reversed-phase column and detected by UV absorption at 254 nm. The mobile phase was a mixture of water–methanol–60% perchloric acid (45:55:0.5, v/v) and was adjusted to pH 8.0 with 25% ammonia solution. Indomethacin was added to the plasma as an internal standard. Methanol was selected for the extraction of both the compounds and internal standard. α-GZ and β-GZ could be precisely determined in concentration of 1 mg/ml in a 0.1 ml sample.