The Development of Immunological Quantification Method for Glycyrrhetinic Acid in Serum to Estimate the Potential Risk for Pseudoaldsteronism

Glycyrrhizae Radix (GR), the dried root and stolon of Glycyrrhiza uralensis or G. glabra, is most frequently used as a crude drug, compounding Kampo medicines to treat a variety of diseases in Japan. This key crude drug, however, would be coinstantaneously a risk factor for pseudoaldosteronism. This adverse effect is thought to be due to glycyrrhetinic acid (GA), a major metabolite of glycyrrhizin, which is one of the ingredients of GR. Therefore, we thought that if the blood GA concentration could be measured quickly and easily when side effects occur, the causal relationship could be clarified, and side effects could be avoided. To realize this plan, we developed the competitive ELISA using anti-GA monoclonal antibody (mAb6D6), which was labeled 'biotin' to avoid endogenous effects, such as antibodies in serum, and to detect GA sensitively. This ELISA could quantify GA from about 10 pg/mL to 25 ng/mL. The quantitative value of GA in serum based on this ELISA was significantly corelated with that of GA based on high-performance liquid chromatography. Hence, the developed competitive ELISA could be an useful tool for users who would like to quantify the blood GA concentration to clarify the relationship between GA and pseudoaldosteronism derived from the intake of medicines containing GR and to lead to avoiding side effects derived from GA.