Absorption and transportation characteristics of scutellarin and scutellarein across Caco-2 monolayer model

Objective: To investigate the absorption and transepithelial transport characteristics of scutellarin and scutellarein in the human colonic adenocarcinoma cell (Caco-2) monolayer model. The influence factors on these two compounds' absorption were investigated, such as buffer solution, duration of culture, and inhibitors of multidrug resistance-associated protein 2 (MRP ₂), breast cancer drug resistance protein (BCRP) and P-glycoprotein (P-gp). Methods: By using Caco-2 monolayer as an intestinal epithelial cell model, the transport process was studied from apical (AP) side to basolateral (BL) side or from BL to AP. The two compounds were determined by high-performance liquid chromatography coupled with diode-array-detector detection. Transport parameters and apparent permeability coeffients (P _app) were calculated. Results: The P_app values of scutellarin and scutellarein were different in two buffer solutions, respectively. In phosphate buffered saline, scutellarin had no absorption from AP to BL, while its P_app value was 0.74 × 10^-6 to 1.58 × 10^-6 cm/s from BL to AP. The P_app values of scutellarein were 4. 33 × 10^-6 to 6.79 × 10^-6 cm/s and 1.32 × 10^-6 to 2.56 × 10^-6 cm/s from AP to BL and from BL to AP, respectively. The P_app value gradually decreased with time. The absorption of scutellarein was better than that of scutellarin. The scutellarin absorption was improved by verapamil, MK-571 and reserpine. The scutellarein absorption was improved by verapamil whereas its excretion was improved by MK-571. Conclusion: Absorption of scutellarin is difficult in Caco-2 monolayer cells, which contributes to its low bioavailability. Scutellarein absorption is better than scutellarin absorption. Scutellarein transepithelial transport is passive diffusion. The inhibitor of P-gp can improve scutellarin and scutellarein transportation. The inhibitors of MRP₂ and BCRP can promote transportation of scutellarin. The inhibitor of MRP₂ can promote efflux of scutellarein. The multidrug resistance-associated protein may be the second reason for low bioavailability of scutellarin.