Determination of gambogic acid in human plasma by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry.

A high-performance liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (HPLC-APCI-MS) method was established for the determination of gambogic acid (GA) in human plasma using ursolic acid as the internal standard (I.S.). Plasma samples were extracted with ethyl acetate and separated on a Hanbon Lichrospher 5-C18 column with a mobile phase of acetonitrile-tetrahydrofuran-water (70:23:7, v/v). Gambogic acid was determined by using atmospheric pressure chemical ionization (APCI) in a single quadrupole mass spectrometer. HPLC-APCI-MS was performed in the selected ion monitoring (SIM) mode using target ions at [M-H](-)m/z 627.4 for gambogic acid and [M-H](-)m/z 455.4 for the I.S. Calibration curve was linear over the range of 3.108-4144 microg/L. The lower limit of quantification was 3.108 microg/L. The intra- and inter-run precisions were less than 12.3 and 14.1%, respectively. The method has been successfully applied to study the pharmacokinetics of gambogic acid in patients with malignant tumour.