Determination of Catalposide in Rat Plasma by Liquid Chromatography-Mass Spectrometry

A liquid chromatography-mass spectrometric method was developed for the quantitative determination of catalposide in rat plasma. The method involved the deproteinization followed by injection onto an XTerra C18 column. Catalposide was eluted at 3.8 min at a flow rate of 0.4 mL/min with the mobile phase of methanol-acetonitrile-ammonium formate (10 mM, pH 4.5) (30:5: 65, v/v). The standard curve was linear (r 2 = 0.997) over the concentration range of 0.05–10 µg/mL with the coefficient of variation of intra- and inter-assay ranged from 1.5–4.8% and 3.4–5.6%, respectively. The limit of quantification was 0.05 µg/mL using a plasma sample of 100 µL. Catalposide was stable in various pH solutions ranging from 2 to 13 for up to 24 h incubation at 37°C. Catalposide was relatively stable in rat whole blood and plasma, human plasma, and rat or human liver microsomes for up to 3 h incubation at 37°C. This method was applied to a pharmacokinetic study after intravenous injection of catalposide (10 mg/kg) to rats.