A rapid and sensitive determination of aucubin in rat plasma by liquid chromatography-tandem mass spectrometry and its pharmacokinetic application.

A sensitive, accurate, rapid and robust LC-MS-MS method for the quantification of aucubin, a major bioactive constituent of Aucuba japonica, Eucommia ulmoides and Plantago asiatica, was established and validated in rat plasma. Plasma samples were simply precipitated by adding methanol and the supernatant was chromatographed by a Diamonsil® C(18)(2) column with the mobile phase comprising a mixture of 10 mm ammonium acetate in methanol and that in water with the ratio of 50:50 (v/v). Quantification of aucubin was performed by mass spectrometry in the multiple-reaction monitoring mode with positive atmospheric ionization at m/z 364 → 149 for aucubin, and m/z 380 → 165 for catalpol (IS), respectively. The retention time was 2.47 and 2.44 min for aucubin and the IS, respectively. The calibration curve (10.0-30,000 ng/mL) was linear (r²  > 0.99) and the lower limit of quantification was 10.0 ng/mL in the rat plasma sample. The method showed satisfactory results such as sensitivity, specificity, precision, accuracy, recovery, freeze-thaw and long-term stability. This simple LC-MS method was successfully applied in a pharmacokinetic study carried out in Sprague-Dawley rats after oral administration of aucubin at a single dose of 50 mg/kg. Herein the pharmacokinetic study of aucubin is reported for the first time.