Previous research in our laboratory found that the absolute bioavailability of vitexin-2''-O-rhamnoside (VR) was quite low at 4.89%. A rapid and sensitive UHPLC method using hesperidin as an internal standard was therefore developed and validated to investigate the reasons for this by determining VR in rat plasma after administering intravenously, intraportally (5 mg/kg), intraduodenally and intragastrically (40 mg/kg) to the rat model of the hepatic, gastric and intestinal first-pass effects. As only a high intestinal first-pass effect of VR was found, that is, there existed a low bioavailability of VR (2.40%), inhibitors of P-glycoprotein (P-gp) and cytochrome P450 3A (CYP3A), including verapamil, cyclosporin A and midazolam, and absorption enhancers, including bile salts and borneol, combined with VR, were instilled into duodenum to evaluate the effects on bioavailability of VR. The results demonstrated that area under the concentration-time curve (AUC) values of VR slightly increased after administration of verapamil, cyclosporin A and midazolam, indicating that CYP3A and P-gp do not play an important role in the first-pass effect in the intestine. AUC values of VR significantly increased after administering bile salts or borneol, indicating that the low bioavailability of VR was mainly related to its poor absorption in the intestine.
Keywords: bioavailability; first-pass effect; vitexin-2”-O-rhamnoside.
Copyright © 2015 John Wiley & Sons, Ltd.