Metabolism and disposition of resveratrol in rats: extent of absorption, glucuronidation, and enterohepatic recirculation evidenced by a linked-rat model.

Pharmacokinetics of trans-resveratrol in its aglycone (RES(AGL)) and glucuronide (RES(GLU)) forms were studied following intravenous (15 mg/kg i.v.) and oral (50 mg/kg p.o.) administration of trans-resveratrol in a solution of beta-cyclodextrin to intact rats. In addition, the enterohepatic recirculation of RES(AGL) and RES(GLU) was assessed in a linked-rat model. Multiple plasma and urine samples were collected and concentrations of RES(AGL) and RES(GLU) were determined using an electrospray ionization-liquid chromatography/tandem mass spectrometry method. After i.v. administration, plasma concentrations of RES(AGL) declined with a rapid elimination half-life (T(1/2), 0.13 h), followed by sudden increases in plasma concentrations 4 to 8 h after drug administration. These plasma concentrations resulted in a significant prolongation of the terminal elimination half-life of RES(AGL) (T(1/2TER), 1.31 h). RES(AGL) and RES(GLU) also displayed sudden increases in plasma concentrations 4 to 8 h after oral administration, with T(1/2TER) of 1.48 and 1.58 h, respectively. RES(AGL) bioavailability was 38% and its exposure was approximately 46-fold lower than that of RES(GLU) (AUC(inf), 7.1 versus 324.7 micromol.h/l). Enterohepatic recirculation was confirmed in the linked-rat model since significant plasma concentrations of RES(AGL) and RES(GLU) were observed in bile-recipient rats at 4 to 8 h. The percentages of the exposures of RES(AGL) and RES(GLU) that were due to enterohepatic recirculation were 24.7 and 24.0%, respectively. The fraction of drug excreted in the urine over a period of 12 h was negligible. These results confirm that RES(AGL) is bioavailable and undergoes extensive first-pass glucuronidation, and that enterohepatic recirculation contributes significantly to the exposure of RES(AGL) and RES(GLU) in rats.