Pharmacokinetics-based identification of pseudoaldosterogenic compounds originating from Glycyrrhiza uralensis roots (Gancao) after dosing LianhuaQingwen capsule

LianhuaQingwen capsule, prepared from an herbal combination, is officially recommended as treatment for COVID-19 in China. Of the serial pharmacokinetic investigations we designed to facilitate identifying LianhuaQingwen compounds that are likely to be therapeutically important, the current investigation focused on the component Glycyrrhiza uralensis roots (Gancao). Besides its function in COVID-19 treatment, Gancao is able to induce pseudoaldosteronism by inhibiting renal 11β-HSD2. Systemic and colon-luminal exposure to Gancao compounds were characterized in volunteers receiving LianhuaQingwen and by in vitro metabolism studies. Access of Gancao compounds to 11β-HSD2 was characterized using human/rat, in vitro transport, and plasma protein binding studies, while 11β-HSD2 inhibition was assessed using human kidney microsomes. LianhuaQingwen contained a total of 41 Gancao constituents (0.01–8.56 μmol/day). Although glycyrrhizin (1), licorice saponin G2 (2), and liquiritin/liquiritin apioside (21/22) were the major Gancao constituents in LianhuaQingwen, their poor intestinal absorption and access to colonic microbiota resulted in significant levels of their respective deglycosylated metabolites glycyrrhetic acid (8), 24-hydroxyglycyrrhetic acid (M2(D); a new Gancao metabolite), and liquiritigenin (27) in human plasma and feces after dosing. These circulating metabolites were glucuronized/sulfated in the liver and then excreted into bile. Hepatic oxidation of 8 also yielded M2(D). Circulating 8 and M2(D), having good membrane permeability, could access (via passive tubular reabsorption) and inhibit renal 11β-HSD2. Collectively, 1 and 2 were metabolically activated to the pseudoaldosterogenic compounds 8 and M2(D). This investigation, together with such investigations of other components, has implications for precisely defining therapeutic benefit of LianhuaQingwen and conditions for its safe use.