Pharmacokinetics of ganoderic acid D and its main metabolite by liquid chromatography-tandem mass spectrometry

The present study aims to investigate the pharmacokinetics of ganoderic acid D (GD), a representative active triterpenoid from Ganoderma lucidum. A sensitive and selective liquid chromatography-tandem mass spectrometry method was developed for the simultaneous determination of the concentrations of GD and its main metabolite (ganoderic acid B) in rat plasma. Following protein precipitation, the analytes were separated on a reversed-phase C18 column. Acetonitrile-water-acetic acid (40:60:0.01) was used at a flow-rate of 0.2 ml/min. A triple quadrupole mass spectrometer equipped with an electrospray ionization source was used as the detector and was operated in the negative ion mode. Multiple reaction monitoring using the characteristic transitions was performed to quantify the analytes. The method had a lower limit of quantification of 8.19 ng/ml for GD, and 8.59 ng/ml for ganoderic acid B (GB). The calibration curves were demonstrated to be linear over the concentration range of 8.19-4096 ng/ml and 8.59-2149 ng/ml, respectively. Variations within- and between-batch were less than 6.4% and 4.6%, respectively. The extraction recovery rates ranged from 98.8 to 105.2% and 100.7 to 113.6%, respectively. The validated method was successfully applied to the quantification of GD and GB concentrations in rat plasma after oral administration (or intravenous administration) of GD preparations at a dose of 15 mg/kg. The data showed that the absolute bioavailability increased from 22% to 70% after the GD suspension was changed to GD loaded solid lipid nanoparticles. In the meantime, the Cmax increased from 107.2 to 1555.6 ng/ml; the tmax changed from 2.0 h to 0.3 h. These results are very helpful in the further studies.