RESUMO
Extracts of bitter melon, soybean, dokudami and welsh onion by 40% methanol increased the accumulation of rhodamine-123 by Caco-2 cells, suggesting that these extracts inhibited P-glycoprotein (P-gp). The extract of bitter melon was separated in a tC18 cartridge column and the eluate from 80% acetonitrile most markedly increased the [(3)H]-daunomycin accumulation by Caco-2 cells. The inhibitory compounds in the bitter melon fraction were isolated by HPLC with Pegasil C4 and Pegasil ODS columns. The HPLC fraction having the highest activity was analyzed by (1)H-NMR and FAB-MS, and the active compound was identified as 1-monopalmitin. The inhibitory activities of 1-monopalmitin and its related compounds suggested that the inhibition of P-gp activity was not dependent on the degree of unsaturation of fatty acid in the monoglyceride, but on the chain length. It was also suggested that the monoglyceride structure played an important role in the inhibition of P-gp activity. Monoglycerides could therefore alter the pharmacokinetics of drugs by inhibiting the P-gp-mediated efflux.
Assuntos
Subfamília B de Transportador de Cassetes de Ligação de ATP/metabolismo , Momordica charantia , Extratos Vegetais/farmacologia , Subfamília B de Transportador de Cassetes de Ligação de ATP/antagonistas & inibidores , Adenocarcinoma/metabolismo , Adenocarcinoma/patologia , Aminoácidos/farmacocinética , Transporte Biológico/efeitos dos fármacos , Células CACO-2 , Cromatografia Líquida de Alta Pressão/métodos , Neoplasias do Colo/metabolismo , Neoplasias do Colo/patologia , Daunorrubicina/farmacocinética , Relação Dose-Resposta a Droga , Frutas , Glicerídeos/farmacologia , Temperatura Alta , Humanos , L-Lactato Desidrogenase/metabolismo , Espectrometria de Massas/métodos , Metanol/química , Extratos Vegetais/isolamento & purificação , Extratos Vegetais/metabolismo , Pronase/metabolismo , Rodamina 123/farmacocinética , VerdurasRESUMO
P-glycoprotein (P-gp) is a 170 kDa membrane protein that belongs to the ATP-binding cassette (ABC) transporter superfamily. In normal tissues, P-gp functions as an ATP-dependent efflux pump that excretes highly hydrophobic xenobiotic compounds, playing an important role in protecting the cells/tissues from xenobiotics. In the present study, chemical substances that could directly modulate the intestinal P-gp activity were searched in vegetables and fruits. By using human intestinal epithelial Caco-2 cells as a model of the small intestinal cells, we observed that a bitter melon fraction extracted from 40% methanol showed the greatest increase of the rhodamine-123 accumulation by Caco-2 cells. Inhibitory compounds in the bitter melon fraction were then isolated by HPLC using Pegasil C4 and Pegasil ODS columns. The HPLC fraction having the highest activity was analyzed by (1)H-NMR and FAB-MS, and the active compound was identified as 1-monopalmitin. It is interesting that certain types of monoglyceride might be involved in the drug bioavailability by specifically inhibiting the efflux mediated by P-gp.
