Permeability of plumbagin across human intestinal cell in vitro

Plumbagin is the active compound isolated from plants used in traditional medicine for treatment of various diseases such as activities malaria, leishmaniasis, viral infections and cancers. The aim of the study was to investigate the permeability of plumbagin across Caco-2 (human epithelial colorectal adenocarcinoma) cell monolayer and its effects on the expression and function of P-glycoprotein. The integrity of Caco-2 cell monolayer was evaluated by measuring trans-epithelial electrical resistance and permeation (Papp) of Lucifer yellow across the cell monolayer. The effect of plumbagin on P-glycoprotein was detected by measuring its interference with the transport of the P-glycoprotein substrate (R123) and the effect on MDR-1 mRNA expression was detected by RT-PCR. The Papp of plumbagin (2-8 µM) for the apical to basolateral and basolateral to apical directions were 10.29-15.96 × 10(-6) and 7.40-9.02 × 10(-6) cm/s, respectively, with the efflux ratios of 0.57-0.73. Plumbagin is not either a substrate or inhibitor of P-glycoprotein. It did not interfere with the P-glycoprotein-mediated R123 transport across Caco-2 cell monolayer, as well as the function of P-glycoprotein and the expression of MDR-1 mRNA. Results suggest moderate permeability of plumbagin across the Caco-2 cell monolayer in both directions. The transport mechanism is likely to be a passive transport.