A UPLC-MS Method for Simultaneous Determination of Geniposidic Acid, Two Lignans and Phenolics in Rat Plasma and its Application to Pharmacokinetic Studies of Eucommia ulmoides Extract in Rats.

The bark of Eucommia ulmoides is a well-known Chinese herbal medicine that is used to regulate blood pressure and reduce blood sugar and fats, as well as an antioxidant and antimicrobial agent. Here we describe the development of a sensitive ultrahigh performance liquid chromatography-tandem mass spectrum method for the simultaneous determination of five major active ingredients of E. ulmoides bark extract, namely, geniposidic acid (GA), protocatechuic acid (PCA), chlorogenic acid (CA), (+)-pinoresinol di-O-β-D-glucopyranoside (PDG) and (+)-pinoresinol 4'-O-β-D-glucopyranoside (PG), in rat plasma. The preliminary steps in the plasma analysis were the addition of an internal standard and acidification (0.1 % formic acid), followed by protein precipitation with methanol. Separation of the active ingredients was performed on an ACQUITY UPLC® BEH C18 column (2.1 × 50 mm; internal diameter 1.7 µm) at a flow rate of 0.35 mL/min, with acetonitrile/water containing 0.1 % formic acid as the mobile phase. Detection was performed on a triple quadrupole tandem mass spectrometer via electrospray ionization source with positive and negative ionization modes. All calibration curves showed good linearity (r ≥ 0.997) over the concentration range with the low limit of quantification between 4.45 and 54.9 ng/mL. Precision was evaluated by intra- and inter-day assays, and the percentages of the relative standard deviation were all within 15 %. Extraction efficiency and matrix effect were 84.3-102.4 % and 98.1-112.2 %, respectively. The validated method was successfully applied to the pharmacokinetic study in rats after oral administration of E. ulmoides extract. The results indicate that the pharmacokinetic properties of GA differ from those of PCA, CA, PDG and PG, respectively.