ABSTRACT
Emodin has numerous biochemical and pharmacological activities, though information about its intestinal absorption and first-pass metabolism is scarce. The purpose of this study was to evaluate intestinal absorption and metabolism of luminally administered emodin in an isolated rat small intestine using the method of LC/MS/MS. About 22.55% of the administered emodin appeared at the vascular side, chiefly as free emodin (12.01%), but some emodin glucuronide (8.69%) and sulfate (1.84%) were also detected. Free glucuronide (5.23%) and sulfate (1.08%) moieties were found in the luminal perfusate. This model serves as a valuable tool for understanding intestinal handling of emodin, and our results confirm absorption and first-pass metabolism of emodin in the rat small intestine. Phase II metabolic enzymes such as glucuronyl transferase or sulfate transferase may also play an important role in the first-pass metabolism of emodin in the small intestine, which may ultimately reduce the bioavailability (and thus the efficacy) of orally administered emodin.
Subject(s)
Cathartics/metabolism , Emodin/metabolism , Intestine, Small/metabolism , Animals , Biological Availability , Chromatography, Liquid , Glucuronides/metabolism , In Vitro Techniques , Intestinal Absorption , Male , Perfusion , Rats , Rats, Sprague-Dawley , Splanchnic Circulation/physiology , Sulfates/metabolism , Tandem Mass SpectrometryABSTRACT
The intestinal absorption characteristics of anthraquinones emodin and chrysophanol were observed by measuring the intracellular accumulation across Caco-2 cells by the reverse-phase high performance liquid chromatography. The intracellular accumulation of chrysophanol was much greater than that of emodin, the maximum absorption of emodin and chrysophanol being 414.02+/-15.28 and 105.56+/-11.57 nmol/l x mg x protein, respectively. The absorption of each anthraquinone was significantly lower at 4 degrees C than that of 37 degrees C. The effects of the transport inhibitors, verapamil, cyclosporine and phloridzin, on the intracellular accumulation were also examined. Verapamil and cyclosporine increased the absorption of emodin and chrysophanol, while phloridzin inhibited their absorption, all in a dose-dependent manner. These results suggest that the absorption characteristics of emodin and chrysophanol were closely related to their special structure with the hydroxy groups. It is also likely that a specific transport system mediated the intracellular accumulation of emodin and chrysophanol across the Caco-2 cells.
