Mechanisms Underlying The Pharmacokinetic Influence Of Glycyrrhizae Radix Et Rhizoma On Berberine In Coptidis Rhizoma

Aim:Coptidis Rhizoma（CRE）has long and widely been used in clinics.Glycyrrhizae Radix et Rhizoma（GRE）has significant influence on the pharmacokinetics of Coptidis Rhizoma alkaloids.However,there are few systematic studies on the pharmacokinetic mechanisms except influences on extract ratio and influences mediated by modulating drug metabolism enzymes.Therefore,based on our previous studies,the pharmacokinetic mechanisms of GRE on CRE were investigated in this study,majorly focusing on influences on the intestinal absorption of berberine.Methods:CRE and the water extract dry powder in different proportions of CRE and GRE were prepared through extraction and drying.The concentration of berberine in the samples was quantitatively analyzed with LC-MS or LC-MS/MS.The influences of GRE on the extracted amount of berberine in CRE were firstly determined.Then the influences of GRE on the pharmacokinetics of berberine in CRE were investigated in mice.The effects of GRE on the solulibity of berberine were studied and the dissolution of berberine in the stomach and intestine fluids were investigated using a dissolution apparatus.The in vitro absorption and efflux of berberine was studied using mice gut sacs.The diffusion rate of berberine was tested via a dialysis experiment.The existence form of berberine in different extracts was qualitatively observed by a laser confocal fluorescence microscopy.Results:The results showed that the AUC_0-12 value of berberine in the portal vein of mice decreased by 36.5%when CRE-GRE is 1:1 and 56.9%when CRE-GRE is 3:1,where the amount of the herb piece of CRE was equal to the control CRE treated group.A two-way analysis of variance showed that the AUC value in CRE treated group was significantly different from CRE-GRE（1:1）group and CRE-GRE（3:1）treated group（all p<0.01）.GRE showed significant influences on the extracted amount,solubility,gastric and intestinal dissolution,intestinal absorption and efflux,diffusion rate,and existing forms of berberine in CRE.The extracted amount of berberine was decreased by 32%;the solubility decreased by 81.3%;and there were significant difference on the dissolution of gastric juice and intestinal juice.In the gastric juice dissolution,the similarity factor（f₂）of CRE group and CRE-GRE（1:1）group was 13.6;in the intestinal juice dissolution,the similarity factor（f₂）of CRE group and the CRE-GRE（1:1）group was 48.3.However,the transfer of berberine across intestinal epithelial cells was promoted by GRE because the intestinal efflux of berberine was inhibited by GRE and the diffusion rate of berberine was improved by GRE.Berberine in CRE was encapsulated by unknown substance in GRE to form precipitates.The results of a pharmacokinetic study indicated that the AUC_0-12 value of berberine in mice that received the precipitate was decreased by 44.1%when compared with the supernatant treated groups,which received same dose of berberine.Conclusion:Although GRE was able to promote the intestinal absorption of berberine by inhibiting its efflux during absorption and improving its diffusion rate,GRE had inhibitory effects on the extracted amount,form,solubility,gastrointestinal dissolution of berberine in CRE,and finally significantly reduced the intestinal absorption and in vivo exposure level of berberine.