UHPLC-MS method for determination of gambogic acid and application to bioavailability, pharmacokinetics, excretion and tissue distribution in rats

A sensitive ultrahigh performance liquid chromatography tandem mass spectrometry (UHPLC-MS) method was developed for determination of gambogic acid (GA) in rat plasma, urine, bile and main tissues. GA was separated on an Agilent Zorbax XDB-C₁₈ column (50×2.1mm, 1.8μm) with gradient mobile phase at the flow rate of 0.2mL/min. The detection was performed by negative electrospray ionization with multiple reaction monitoring mode. The calibration curves of GA were linear between 1.0 and 1000ng/mL in rat plasma and bile and between 1.0 and 500ng/mL in urine and tissues. The lowest limit of quantification for all matrices was 1.0ng/mL. Both accuracy and precision of the assay were satisfactory. This validated method was firstly applied to bioavailability (BA), pharmacokinetics, excretion and tissue distribution in rats. The BAs of GA (40 and 80mg/kg) in rats were 0.25 and 0.32%, respectively. GA was distributed extensively in rats after oral administration and exhibited the highest level in liver. GA reached the cumulative excretion amount of 25.3±1.7μg in bile and 0.275±0.08μg in urine after i.g. 80mg/kg to rats at 24h. The present results would be helpful for further clinical use of GA as a potential anticancer drug.