Presence or absence of a gallate moiety on catechins affects their cellular transport

The accumulation of (-)-epicatechin (EC), a non-gallate catechin, was significantly lower than that of (-)-epicatechin gallate (ECG), a gallate catechin, in Caco-2 cells. Using Caco-2 cell monolayers cultured in transwells, the transport of catechins in the basolateral-to-apical direction was much higher than that in the apical-to-basolateral direction, suggesting the involvement of an efflux transporter. Moreover, the results suggest that involvement of a transporter in EC efflux is greater than that for ECG. Treatment with transporter inhibitors MK571, quinidine or mitoxantrone, which inhibit MRP2 P-glycoprotein (P-gp) and BCRP, respectively, led to an increase in the accumulation of EC into Caco-2 cells and a decrease in the P-app ratio (P-app B -> A/P-app A -> B) for EC. These transporters seemed to be involved in EC efflux. BCRP was not an efflux transporter for ECG, and the influences of MRP2 and P-gp on ECG efflux were lower than for EC. Thus, efflux transporters appear to be responsible for the difference in cellular accumulation of EC versus ECG, suggesting that the presence or absence of a gallate moiety in the catechin structure influences the transporters.