The present study was designed to investigate the effects of aqueous fruit extract of Momordica charantia (MC), a traditional medicinal plant, on the transport of fluid in vitro. Everted intestinal sacs from rats were mounted in an organ bath containing Krebs solution. We compared the effect of MC extract on water transport with increasing inorganic phosphate concentration with or without D-glucose in the buffer. In the control experiments, fluid uptake was enhanced significantly (P < 0.05) at high inorganic phosphate concentration (8-10 mM) in the presence of 5.5 mM D-glucose. Addition of 3.0 mg/mL MC extract to the serosal side inhibits the uptake of fluid significantly (P < 0.05). At high inorganic phosphate concentration (8-10 mM), fluid uptake was not inhibited (P > 0.05) when incubated with 3.0 mg/mL MC fruit extract. It is hypothesized that an increase in inorganic phosphate enhances oxidative phosphorylation thereby increasing the fluid uptake across everted intestinal sacs of rat. These findings seem to indicate that the MC-induced reduction on intestinal fluid absorption capacity could be mainly the result of an interference with the carrier-mediated coupled entrance of glucose and Na(+) across the brush-border membrane.