Pharmacokinetics-based Identification Of Potential Pseudoaldosterogenic Compounds Originating From Glycyrrhiza Uralensis Roots (Gancao) After Dosing LianhuaQingwen Capsule

Objective:Lianhua Qingwen capsule,prepared from a combination of 11 herbs,gypsum,and l-menthol,is officially recommended as treatment for COVID-19 in China.Serial pharmacokinetic investigations of Lianhua Qingwen were designed to identify its compounds having therapeutic potential.This investigation focused on the component herb Glycyrrhiza uralensis roots（Gancao）,excess use of which can induce pseudoaldosteronism by inhibiting renal 11β-HSD2.The aim of this investigation was to identify its Gancao compounds having therapeutic potential,particularly potential pseudoaldosterogenic Gancao compounds of Lianhua Qingwen.Methods:Systemic exposure to Gancao compounds and their access to the colonic microbiota were determined in human volunteers receiving Lianhua Qingwen and were characterized by in vitro metabolism and rat studies.Access of glycyrrhetic acid and related compounds to renal 11β-HSD2 were characterized using in vitro transport,plasma protein binding,and rat studies,while the enzyme inhibition was assessed using human kidney microsomes.Literature-mined information was used to facilitate the experimental studies,with their samples,as well as the dosed Lianhua Qingwen sample,being analyzed by liquid chromatography/mass spectrometry.Results:Although the saponin glycyrrhizin and the flavonoids liquiritin and liquiritin apioside were the major Gancao constituents of Lianhua Qingwen,access to the colonic microbiota due to poor gut absorption resulted in significant levels of their respective deglycosylated metabolites glycyrrhetic acid and liquiritigenin in human plasma samples and fecal samples（glycyrrhetic acid only）after dosing the capsule.Glycyrrhetic acid was jointly eliminated by sulfation,glucuronidation,and hydroxylation,followed by hepatobiliary excretion;similar scenario occurred with liquiritigenin,but its glucuronides were detectable in blood.Glycyrrhetic acid has a very high plasma protein binding,and the unbound fraction in plasma is only 0.07%.Its renal excretion was very slow and involved tubular reabsorption,as indicated by renal clearance ratios of 0.2 in volunteers receiving Lianhua Qingwen.The results of in vitro membrane permeability and transporter transport of licorice components suggested that glycyrrhetic acid is not a substrate for the renal uptake transporters,it has good membrane permeability that can pass through the membrane and reach the target by passive diffusion.It is worth mentioning that glycyrrhetic acid has strong inhibitory activity on human11β-HSD2 with IC₅₀ value 0.01μmol/L,which is the most inhibitory Gancao compound.Conclusion:To our knoeledge,the human pharmacokinetic data originating from Gancao of Lianhua Qingwen are reported here for the first time.Based on systemic exposure and access to and inhibition of renal 11β-HSD2,glycyrrhetic acid was identified as a potential pseudoaldosterogenic Gancao compound in Lianhua Qingwen.This investigation,together with such investigations for the other component herbs,facilitates better defining therapeutic benefit of Lianhua Qingwen and conditions for its safe use.