Simultaneous determination of magnolin and epimagnolin A in rat plasma by liquid chromatography with tandem mass spectrometry: Application to pharmacokinetic study of a purified extract of the dried flower buds of Magnolia fargesii, NDC-052 in rats

A purified extract isolated from the dried flower buds of Magnolia fargesii (NDC-052) is currently being evaluated for phase III clinical trials as a new anti-asthma drug. A rapid, sensitive and selective liquid chromatography–tandem mass spectrometric (LC/MS/MS) method for the simultaneous determination of magnolin and epimagnolin A, the major bioactive components of NDC-052, in rat plasma was developed. After liquid–liquid extraction with tolterodine as an internal standard, magnolin and epimagnolin A were separated on a Luna phenyl-hexyl column with the mobile phase of 70% methanol in 10 mM ammonium formate. The analytes were detected by an electrospray ionization tandem mass spectrometry in the multiple-reaction-monitoring mode. The standard curves were linear over the concentration range of 50–2500 ng/mL for magnolin and epimagnolin A in rat plasma. The intra- and inter-day coefficients of variation and relative errors for magnolin and epimagnolin A at four QC concentrations were 1.5–11.4% and 5.9–12.5%, respectively. The lower limits of quantification for magnolin and epimagnolin A were 50.0 ng/mL using 50 μL of plasma. This method was successfully applied to the pharmacokinetic study of magnolin and epimagnolin A after an oral administration of NDC-052 in male Sprague–Dawley rats.