Study On The Effects Of Glycyrrhizic Acid And Glycyrrhetinic Acid On The Bioavailability Of Paeoniflorin

Traditional Chinese medicine White Peony Root is the dry root of Pulsatilla chinensis (Bge.) Regel (Ranunculaceae), which is recorded in the first edition of China Pharmacopeia in2010.The herb is widely used to nourish blood for regulating menstruation and to repress the liver, which had been proved by the pharmacological and clinical research. Glycyrrhiza uralensis is the dry root and rhizome of leguminous plant Glycyrrhiza uralensis Fisch, Glycyrrhiza in flata Bat, Glycyrrhiza glabra L. Glycyrrhiza uralensis is one commonly used Chinese medicine with multi-effectiveness. Glycyrrhizic acid and glycyrrhetinic acid are the main active component of glycyrrhiza uralensis. Peony and licorice decoction was first found in Treatise on Febrile Diseases by Zhang Zhongjing, which had the effects of sedation, analgesic, antispasmodic and anti-inflammation.We initially investigated the bioavailability of paeoniflorin in vivo and the effect of glycyrrhizic acid or glycyrrhetinic acid on bioavailability of paeoniflorin by the rat in vivo kinetic models in the studies. It would help us to understand the rationality of concert application of herbs. After the administration of paeoniflorin alone or with glycyrrhizic acid and glycyrrhetinic acid, blood samples were collected and assayed by LC-MS, the plasma concentration-time profiles of paeoniflorin were established. Pharmacokinetic parameters were calculated and analyzed with DAS2.1.1software. Pharmacokinetics data indicated that glycyrrhizic acid can reduce the Cmax, Tmax and AUC of paeoniflorin, while glycyrrhetinic acid can increase the parameters. After the administration of glycyrrhizic acid or glycyrrhetinic acid for senen days, the conclusion was the same as it. The main active component of glycyrrhiza uralensis can affect the oral absorption and the bioavailability of paeoniflorin.In addition, the effects of glycyrrhizic acid and glycyrrhetinic acid on the intestinal absorption of paeoniflorin were investigated by the rat intestinal perfusion model. The results indicated that the apparent absorption reaction constant decreased and the conversion of absorption of paeoniflorin both decreased by the use of glycyrrhizic acid. So glycyrrhizic acid can inhibit the intestinal absorption of paeoniflorin while glycyrrhetinic acid showed the opposite effects. The results indicated that the apparent absorption reaction constant and the conversion of absorption of glycyrrhizic acid and glycyrrhetinic acid both increased by the use of digoxin and cyclosporin. Which showed digoxin and cyclosporin had significant effect on the intestinal absorption of glycyrrhizic acid and glycyrrhetinic acid. Digoxin is the substrate of P-gp and cyclosporin is the inhibitor of MRP2and P-gp. So we indicated that glycyrrhizic acid and glycyrrhetinic acid may affect the absorption and bioavailability of paeoniflorin by the regulation effect of P-gp、MRP2.Western blot analysis was used to measure the P-gp of intestinal tissue. The results indicated that the expressing quantity of P-gp apparently increased after glycyrrhizic acid was given for seven days. But the expressing quantity of P-gp apparently decreased by the use of glycyrrhetinic acid. RT-PCR analysis was used to measure the expressing quantity of MDR1to provide evidence for regulation effect of P-gp. The results showed that the expressing quantity of MDR1apparently was increased by the use of glycyrrhizic acid while glycyrrhetinic acid can inhibit the expressing quantity of MDR1.Recent studies show that the expressing quantity of MDR1is mediated by pregnane X receptor (PXR). Western blot analysis was used to measure the expressing quantity of PXR for HepG-2cells treated by glycyrrhizic acid and glycyrrhetinic acid. Rifampicin was served as the positive control group. After HepG-2cells were treated by glycyrrhizic acid for48hours, the expressing quantity of PXR was increased apparently. When treated by glycyrrhetinic acid, it had tendency to increase the expressing quantity of PXR, but had no significant difference. The regulation effect of PXR may be one of the reasons why glycyrrhizic acid affected P-gp. Glycyrrhetinic acid may affect P-gp by other receptors or in other ways, which deserves further studies.In this study, the effects of glycyrrhizic acid and glycyrrhetinic acid on the bioavailability of paeoniflorin were explained from the point of biopharmaceutics by various pharmacokinetics models. The final conclusion can be obtained that the transfer protein mediating the absorption of paeoniflorin in vivo can be regulated by glycyrrhizic acid and glycyrrhetinic acid, further, which could influence the absorption of paeoniflorin, leading the influence of the bioavailability of paeoniflorin in vivo eventually.