A Sensitive Liquid Chromatography-Mass Spectrometry Method for Determination of 14-Deoxy-12(R)-Sulfo Andrographolide Concentration in Rat Plasma and its Application to a Pharmacokinetic Study

Background: Andrographolide is a promising natural substance with numerous pharmacotherapy uses. 14-deoxy-12(R)-sulfo andrographolide (SAP) is the main metabolite of andrographolide in the intestine. Objective: To investigate the pharmacokinetic properties of SAP, a precise and sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the determination of SAP concentration in rat plasma was developed and validated in this study. Methods: Chromatographic separation was achieved on an Acpuity UPLC BEH C18 column with gradient elution that consisted of methanol and water at a flow rate of 0.3 mL/min. MS/MS detection was carried out by the multiple reaction monitoring (MRM) mode with negative electrospray ionization (ESI-) source, with the transitions of m/z 413.2→m/z 287.2 for SAP and m/z 269→m/z 133 for genistein [which was used as an internal standard (IS)]. Results: The calibration curve of SAP was linear over the concentration range of 5-120 ng/mL. The selectivity, precision, accuracy, extraction recovery, matrix effect, and stability of the method were within acceptable ranges. This SAP quantification method was then successfully applied to a pharmacokinetic study of SAP. The area under the curve (AUC) of SAP in rats treated with SAP at 60 mg/kg by intravenous administration was 7498.53 ± 2405.02 mg/L·min. The AUC of SAP in rats treated with SAP at 60 mg/kg by oral administration was 97.74 ± 39.56 mg/L·min. Thus, the absolute oral bioavailability of SAP was determined to be 1.40%.