A high-performance liquid chromatographic method for determination of mitragynine in serum and its application to a pharmacokinetic study in rats

A simple HPLC technique for determining mitragynine levels in serum was developed. The separation system consisted of a C-18 column heated to 35 degrees C, a methanol-water (80:20, v/v) mobile phase, a flow rate of 0.8 mL/min and detection in the ultraviolet at 225 run. Mitragynine, with a retention time of 10.09 min, was well resolved from any interferences in human serum and the internal standard peak. The calibration curve was linear from 0.1 to 10 mu g/mL (r = 0.9995). Extraction of mitrag nine from alkalinized serum using diethyl ether gave a high recovery (>= 85%). The intra- and inter-day precisions of the method were 4.29-5.88% RSD and 7.06-8.45% RSD, respectively. The accuracy ranged from -9.54 to +0.67%DEV. The limit of detection was 0.03 mu g/mL and the lower limit of quantification was 0.1 mu g/mL. Mitragynine in the stock solution was stable during 30 days of storage at 4 degrees C. This method was successfully applied to determine the pharmacokinetic characteristics of mitragynine levels in the serum of rats after it was administered orally. Copyright (c) 2007 John Wiley & Sons, Ltd.