Pharmacokinetics of Sijunzi decoction in rat plasma after oral administration using ultra‐high‐performance liquid chromatography electrospray ionization quadrupole–time of flight mass spectrometry

Sijunzi decoction (SJZD) is one of the most well‐known traditional Chinese herbal formulations. This study elucidates the pharmacokinetics of SJZD in rat plasma after the administration of a single oral dose of 3 mL/kg using ultra‐high‐performance liquid chromatography electrospray ionization quadrupole–time of flight mass spectrometry (UHPLC‐ESI‐Q‐TOF/MS) with bergapten as an internal standard. The separation was performed on an Agilent Zorbax Eclipse Plus C18 column (2.1 × 50 mm, 1.8 μm) by elution with acetonitrile and water (containing 0.1% formic acid) at a flow rate of 0.3 mL/min. Electrospray ionization in positive and negative ion modes was used to quantify six compounds, with monitored ion m/z values of 249.1397 [M + H]+ and 529.3857 [M + H]+ for atractylenolide III (ATL‐III) and pachymic acid (PA), respectively, and m/z of 1107.6638 [M − H]−, 991.5746 [M – H + HCOO]−, 821.3714 [M − H]−, 469.3315 [M − H]− for ginsenoside Rb1, Re, glycyrrhizic acid (GL), and glycyrrhetinic acid (GA), respectively. The calibration curves for ginsenoside Rb1, Re, ATL‐III, PA, GL and GA were 0.0015–0.75, 0.001–0.5, 0.0004–0.2, 0.003–0.9, 0.0015–0.3 and 0.001–1.5 μg/mL, respectively. The intra‐ and inter‐day precisions (RSD) were