Effects of friedelin on the intestinal permeability and bioavailability of apigenin

Although apigenin possesses diverse pharmacological activities, its utilization as a bioactive substance is limited by poor oral bioavailability. The aim of this study was to improve the bioavailability of apigenin by co-administration of friedelin.

To achieve this, the intestinal permeability of apigenin in the absence or presence of friedelin was investigated in both Caco-2 cells and single-pass rat intestinal perfusion models.

The apparent permeability coefficients (P_app) of apigenin in the presence of friedelin were substantially increased by 1.63- and 1.60-fold in Caco-2 cells and single-pass rat intestinal perfusion models, respectively. Such increases in the P_app indicated that friedelin could significantly enhance the absorption of apigenin into the body. The increased bioavailability of apigenin in rats following the oral administration of apigenin 50mg/kg body weight with friedelin 50mg/kg body weight was further confirmed by increases in the peak concentration of apigenin (C_max), elimination half-life (T_1/2) and area under the plasma concentration-time curve (AUC).

Friedelin suppressed ATPase activity of P-glycoprotein (P-gp) indicated that the improved bioavailability of apigenin may be ascribed to P-gp inhibition by the co-administered friedelin.