Determination and pharmacokinetics of evodiamine in the plasma and feces of conscious rats

Evodiamine is one of the major quinazolinocarbolin alkaloids isolated from the fruit of dried unripened Evodia rutaecarpa Bentham. The aim of the present study is to develop an automated blood sampling method to evaluate the oral bioavailability of evodiamine in a conscious freely moving rat. The blood was collected by an automated blood sampling system after evodiamine was administered at doses of 1 and 500 mg/kg through oral and intravenous administration, respectively. The fecal samples were collected by a metabolic cage over five consecutive days after the evodiamine was given orally administered to the rats. Acetonitrile was used to extract evodiamine from the feces and plasma samples. After centrifugation (8000 × g, 10 min), 20 μl aliquot of supernatant were passed through a filter before injection into an HPLC/UV system. The analytes were separated on RP-phenyl column (150 mm × 4.6 mm i.d., particle size 5 μm) at room temperature, and eluted with acetonitrile-water (60:40 (v/v), pH 2.5 adjusted by H3PO4) with a flow-rate of 1.3 ml/min. The UV detector was set at 227 nm. The limit of detection of evodiamine was 0.01 μg/ml in rat plasma and feces. The concentration–response relationship from the present method indicated linearity over a concentration range of 0.01–50 μg/ml. Intra- and inter-assay precision and accuracy of evodiamine in the biological fluids fell well within the predefined limits of acceptability (<15%). Biological fluids were thereby sampled following a dose of evodiamine (500 mg/kg, p.o.). The oral bioavailability was estimated to be about 0.1% in the conscious rat system.