Pharmacokinetics of seven major active components of Mahuang decoction in rat blood and brain by LC–MS/MS coupled to microdialysis sampling

A new highly specific high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS) method coupled to microdialysis sampling was developed and validated for simultaneous determination of L-ephedrine, D-pseudoephedrine, L-methyl-ephedrine, cinnamic acid, liquiritin, amygdalin, and glycyrrhizic acid both in rat blood and brain after oral administration of Mahuang decoction in this paper. An Agilent Zorbax SB-C18 using the 0.1% formic acid water solution and acetonitrile as mobile phase with a gradient elution was applied to the chromatographic separation. The ion transitions were quantified in positive mode for D-pseudoephedrine, L-ephedrine, L-methylephedrine, and diphenhydramine (internal standard), while negative mode for liquiritin, glycyrrhizic acid, amygdalin, cinnamic acid, and prednisolone (internal standard). Several parameters of the method including linearity, accuracy, precision, stability, and matrix effect were within acceptable ranges. The results showed the LC-MS/MS method coupled to microdialysis sampling can be utilized for the pharmacokinetic studies of these seven ingredients in vivo. According to the pharmacokinetic results, the pharmacokinetic parameters of L-ephedrine, D-pseudoephedrine, L-methylephedrine, glycyrrhizic acid, cinnamic acid, liquiritin, and amygdalin were totally different in rat blood and brain, the bioavailability of ephedrine and amygdalin in the blood and brain was higher, while the MRT of ephedrine was the shortest. In the rat brain, the elimination rate of three Ephedra alkaloids was lower than that of the remaining four components. This research offered more basic pharmacokinetic information on the safety mechanisms of Mahuang decoction.