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 (RESAGL) and glucuronide (RESGLU) 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 RESAGL and RESGLU was assessed in a linked-rat model. Multiple plasma and urine samples were collected and concentrations of RESAGL and RESGLU were determined using an electrospray ionization-liquid chromatography/tandem mass spectrometry method. After i.v. administration, plasma concentrations of RESAGL 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 RESAGL (T-1/2TER, 1.31 h). RESAGL and RESGLU 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. RESAGL bioavailability was 38% and its exposure was approximately 46-fold lower than that of RESGLU (AUC(inf), 7.1 versus 324.7 mumol.h/l). Enterohepatic recirculation was confirmed in the linked-rat model since significant plasma concentrations of RESAGL and RESGLU were observed in bile-recipient rats at 4 to 8 h. The percentages of the exposures of RESAGL and RESGLU 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 RESAGL is bioavailable and undergoes extensive first-pass glucuronidation, and that enterohepatic recirculation contributes significantly to the exposure of RESAGL and RESGLU in rats.