Measurement and pharmacokinetic study of plumbagin in a conscious freely moving rat using liquid chromatography/tandem mass spectrometry

The aim of the present study is to develop an automated blood sampling (ABS) method coupled to a liquid chromatography–tandem mass spectroscopy (LC–MS/MS) method to evaluate the oral bioavailability of plumbagin in a conscious freely moving rat. Plumbagin, an herbal ingredient, was isolated from Plumbago zeylanica L. The separation was performed using a reversed phase C18 (150mm × 4.6 mm I.D.; 5 μm) column and was eluted with the mobile phase of water–acetonitrile (40:60, v/v) at a flow-rate of 0.8 ml/min. Multiple reaction monitoring (MRM) was used to monitor the transition of the deprotonated molecule m/z 187 [MH]− to the product ion m/z 159 [MHCO]− for the plumbagin analysis. The calibration curve was linear over the concentration range of 10–2000 ng/ml with a coefficient estimation of 0.995. The intra- and inter-day variations (% relative standard deviation; RSD and % bias) of the assay for rat plasma samples were less than 17%. The limit of detection and the limit of quantification were 5 and 10 ng/ml, respectively. Recovery of plumbagin from the rat plasma was about 80%. This LC–MS/MS method has been validated to study the pharmacokinetics of plumbagin in rats. The oral bioavailability (AUCPO/DosePO)/(AUCIV/DoseIV) of plumbagin was about 38.7 ± 5%.