Caco-2 cells with Transepithelial electrical resistance (TEER) (TEER= (Resistance sample -Resistance blank)×Effective Membrane Area) = 450 ± 19 Ω•cm2 Ω•cm 2 were used for the experiment. Compounds were dissolved in appropriate buffer (10 mM DMSO stock solutions were diluted with HBSS buffer to a final concentration of 10 µM testing compound and 0.4% DMSO, Lucifer Yellow was introduced in the apical side buffer to test the intactness of the mono-cell layer) and was applied to the apical or basolateral donor side for measuring A -B or B -A permeability (two replicates), respectively. The apical and basolateral plates were prewarmed to 37 °C before placing the apical plate onto basolateral plate. After incubating at 37 °C for 90 min, the apical plate and basolateral plate were separated, and the donor or receiver samples were analyzed with UPLC-MS/MS.