Purpose: Four flavones, namely Apigenin, Baicalein, Chrysin and Luteolin, were selected for study and comparison of their absorption and metabolism in gut using the in vitro Caco-2 monolayer model.
Methods: Transport of the four flavones in the Caco-2 monolayer model was studied in both Apical-to-Basolateral and Basolateral-to-Apical directions.
Results: All of the selected flavones were able to pass through the Caco-2 cell monolayer with no significant efflux. The permeability coefficients of the four compounds were all greater than 10(-6) cm/sec and those of Apigenin and Baicalein were even greater than 10(-5) cm/sec. Glucuronides of the tested flavones were all formed in the Caco-2 cell monolayer model and a structure-activity relationship has been proposed for this glucuronidation. In addition, Apical-to-Basolateral transport studies were performed in Caco-2 models pre-treated with Chrysin, an UGT inducer. Quantities of the corresponding glucuronides formed were all significantly higher in Chrysin-treated groups than the controls.
Conclusions: It demonstrated that all selected flavones were substrates of the UGT isoforms that are inducible by Chrysin.