Enterohepatic Circulation and Pharmacokinetics of Genistin and Genistein in Rats.

Genistin and its aglycone genistein of isoflavone are naturally occurring in plants. The aim of this study is to develop an experimental animal model of enterohepatic circulation to investigate the metabolic biotransformation of genistin and genistein in rats. A paired-rat model was developed in which the drug was administered intravenously to the donor rat whose bile duct was cannulated into the duodenum of the untreated recipient rat. The blood sample was collected from the jugular vein of the donor and recipient rats after genistin administration. The results demonstrate that genistein was detected in both the donor and recipient rats after genistein administration (50 mg/kg, iv) in the donor rat, which suggested that the enterohepatic circulation of genistein occurred. The same phenomenon happened again in the biotransformation after genistin administration (50 mg/kg, iv) in the donor rat. Genistein was detected in the recipient rat's blood sample after treatment with β-glucuronidase, which suggested that enzymatic hydrolysis occurred in the transformation of genistin into genistein. In conclusion, the research revealed the metabolic pathway of the glucuronidation of genistin into genistein.