OBJECTIVETo improve the method of indirubin in serum by HPLC and apply to pharmacokinetics in rats.

METHODChromatographic separation was conducted on an C18 column (4.6 mm x 250 mm, 5 microm), using a mixture of methanol-water (75:25) as mobile phase at a flow rate of 1.0 mL min(-1) with UV detection at 289 nm, the column temperature was at 35 degrees C and ethinyl estradiol was used as an internal standard. Rats were administered i. v. bolus of indirubin in doses of 2.0 and 4.0 mg x kg(-1) through a jugular vein catheter, respectively. Serial blood samples (about 100 microL) were individually collected at 2, 5, 10, 20, 30, 60, 90, 120, 180 min after administration, and the concentrations of indirubin determined were in rat serum by HPLC. The pharmacokinetic parameters were calculated with the Winnonlin 5.0 software.

RESULTThe calibration curve for indirubin was linear ( R2 = 0.9996) in the range of 0.031-2.48 mg x L(-1) and the limit of detection (LOD) was 31 microg x L(-1). The average recovery of indirubin in rat serum was more than 98% and the relative standard deviations of intra-day and inter-day were both less than 10%. The pharmacokinetics of Indirubin in rats was fitted to two-compartment model.

CONCLUSIONThe method is simple and accurate with a high sensitivity and a good repeatability, and it can be applied to the evaluation of pharmacokinetic parameters of indirubin in rats and blood concentration of indirubin in clinical controlling.