Characterization of metabolites in rat plasma after intravenous administration of salvianolic acid A by liquid chromatography/time‐of‐flight mass spectrometry and liquid chromatography/ion trap mass spectrometry

<jats:title>Abstract</jats:title> <jats:p> Salvianolic acid A (SalA) is one of the main active constituents in <jats:italic>Salvia miltiorrhiza</jats:italic> (Danshen). Although the pharmacokinetics of SalA in rats after intravenous (i.v.) administration of Danshen injection has been reported, the information relevant to the metabolites of SalA <jats:italic>in vivo</jats:italic> is absent so far. In this study, by means of liquid chromatography with time‐of‐flight mass spectrometry (LC/TOFMS) and liquid chromatography with ion trap mass spectrometry (LC/MS <jats:sup>n</jats:sup> ) techniques, the unknown metabolites of SalA in rat plasma after i.v. administration of the purified SalA at the dose of 20 mg/kg body weight were identified. A liquid‐liquid extraction method was established to separate the metabolites from the plasma and the chromatographic separations were performed on a Xterra MS C <jats:sub>18</jats:sub> column (100 mm × 4.6 mm i.d., 3.5 µm) with acetonitrile/methanol/water/formic acid (20.5:19.5:64: 0.05, v/v/v/v) as the mobile phase at a constant flow rate of 0.2 mL/min. Based on the data obtained from the LC/TOFMS determination (the total ion chromatograms, MS spectra and extracted ion chromatograms), in combination with the characteristic fragment ions acquired from the LC/MS <jats:sup>n</jats:sup> determination, five metabolites were identified as SalA‐monoglucuronide, monomethyl‐SalA‐monoglucuronide, mono‐methyl‐SalA, dimethyl‐SalA and dimethyl‐SalA‐monoglucuronide, and the possible chemical structures were deduced. The results indicated that SalA might mainly undergo two metabolic pathways <jats:italic>in vivo</jats:italic> in rats, which were methylation and glucuronidation. The present studies have laid a solid foundation for the metabolic mechanism of SalA <jats:italic>in vivo</jats:italic> . Copyright © 2009 John Wiley & Sons, Ltd. </jats:p>