Determination of ginsenoside Rd in dog plasma by liquid chromatography-mass spectrometry after solid-phase extraction and its application in dog pharmacokinetics studies.

A sensitive liquid chromatography-mass spectrometric (LC/MS) method for the quantification of ginsenoside Rd in dog plasma was developed and validated after solid-phase extraction (SPE). Chromatographic separation was achieved on a reversed-phase Cromosil C(18) column with the mobile phase of acetonitrile-ammonium chloride (500 micromol/L) and step gradient elution resulted in a total run time of about 5.5 min. The analytes were detected by using an electrospray negative ionization mass spectrometry in the selected ion monitoring (SIM) mode. A good linear relationship was obtained in the concentration range studied (0.005-2.500 microg/mL) (r=0.9998). Lower limit of quantification (LLOQ) was 5 ng/mL by using 500 microL plasma sample. Average recoveries ranged from 70.71 to 75.89% in plasma at the concentrations of 0.010, 0.100 and 2.500 microg/mL. Intra- and inter-day relative standard deviations were 8.49-11.71 and 5.71-16.48%, respectively. This method was successfully applied to the pharmacokinetic studies on dogs. The absolute bioavailability of Rd in dogs was 0.26%.