Simultaneous Determination of Baicalein, Baicalin, Wogonin, and Wogonoside in Rat Plasma by LC-MS/MS for Studying the Pharmacokinetics of the Standardized Extract of Scutellariae Radix

A new composition of standardized Scutellariae Radix extract (HPO12) was developed for treatment of Alzheimer's disease. For the preclinical pharmacokinetic study of HPO12, a rapid, sensitive, and selective LC-MS/MS method was developed and validated for the simultaneous determination of 4 bioactive compounds, baicalein, baicalin, wogonin, and wogonoside. After extraction with ethylacetate, chromatographic analysis was performed on a Thermo C-18 column (150 mm x 2.1 mm, 3 mu m) with a mobile phase consisting of 0.1% formic acid (A) and 0.1% formic acid in 95% acetonitrile (B) by using gradient elution at a flow rate of 250 mu L/min. Analytes introduced to a mass spectrometer were monitored by multiple reaction monitoring (MRM) in positive ion mode. Using 25 mu L of plasma sample, the method was validated over the following concentration ranges: 25-5000 ng/mL for baicalein, 20-40000 ng/mL for baicalin, 1-1000 ng/mL for wogonin, and 5-10000 ng/mL for vogonoside. The intra- and inter-day precision and accuracy of the quality control samples at the 4 concentrations showed <= 13.7% relative standard deviation (RSD) and 86.6-105.5% accuracy. The method was successfully applied to determine the concentrations of baicalein, baicalin, wogonin, and wogonoside in rat plasma after intraperitoneal and oral administrations of HPO12.This research was supported by a grant (09172KFDA996) from Korea Food & Drug Administration in 2011