Rosmarinic acid, the active component of , improves gliquidone transport by regulating the expression and function of P-gp and BCRP in Caco-2 cells.

(Danshen) is typically used in the treatment of diabetic complications and is often co-prescribed with gliquidone in China. However, whether danshen affects the absorption of gliquidone has not been elucidated. In this study, the effects of an aqueous extract of danshen (danshen injection, DSI) and its primary compounds (danshensu, protocatechuic aldehyde, rosmarinic acid and salvianolic acid B) on gliquidone transport across Caco-2 monolayer cells was investigated. DSI enhanced the transport of gliquidone in Caco-2 cell monolayers from the apical (AP) to basolateral (BL) sides and from the BL to AP sides. Rosmarinic acid (RA) also significantly increased the Papp (AP-BL) value for gliquidone transport. Verapamil (a P-gp inhibitor) and Ko143 (a BCRP inhibitor) inhibited the BL-AP transport of gliquidone and promoted the AP-BL transport of gliquidone, whereas MK571 (an MRP1 inhibitor), probenecid (an MRP2 inhibitor), and benzbromarone (an MRP3 inhibitor) had no effect on gliquidone transport. RA also enhanced the intracellular accumulation of Rho123 and Hoechst 33342. The expression of P-gp and BCRP was significantly downregulated, and P-gp ATPase activity was promoted by RA in a dose-dependent manner. These results indicate that an aqueous extract of danshen can increase the transport of gliquidone in Caco-2 cell monolayers and that RA may be the primary compound associated with this activity, which is in agreement with RA simultaneously suppressing the function and expression of P-gp and BCRP.