The efflux of flavonoids morin, isorhamnetin-3-O-rutinoside and diosmetin-7-O-β-D-xylopyranosyl-(1-6)-β-D-glucopyranoside in the human intestinal cell line Caco-2

Purpose. In this study, we chose three of the flavonoids isorhamnetin-3-O-rutinoside(IRR) diosmetin-7-O-beta-D-xylopyranosyl-(1-6)-beta-D-glucopyranoside(DXG) and morin, which showed obvious efflux, to test the hypothesis that a specific efflux transporter is responsible for their transportation. Methods. The intestinal epithelial membrane transport of the flavonoids were examined using the monolayer of the human Caco-2 cell line grown in Transwells, a common model of intestinal absorption. The flavonoids were measured by high performance liquid chromatography with UV detector. Result. The efflux of morin, IRR and DXG, across Caco-2 cell monolayers was examined over the concentration range from 2 to 200 mu M and showed a saturable process. The depletion of the cellular ATP stores with 5 mM iodoacetamide led to a significant inhibition of the efflux. Fifty micromolar verapamil, a chemical inhibitor of P-glycoprotein, had no effect on the transport of the three flavonoids, while the presence of 50 mu M MK-571 and 1 mM probenecid, MRP inhibitors, resulted in an obvious reduction in the efflux. Moreover, inhibition of morin transport by MK-571 demonstrated concentration dependence. The transportation of the three flavonoids was compared with apigenin. Conclusion. These data support a role for MRPs in the intestinal transcellular efflux of morin, IRR, DXG and possibly other hydrophilic flavonoid aglycons and glycosides.