Comparative pharmacokinetics of baicalin and wogonoside by liquid chromatography-mass spectrometry after oral administration of Xiaochaihu Tang and Radix scutellariae extract to rats.

The aim of this study was to compare the pharmacokinetics of baicalin and wogonoside in rats following oral administration of Xiaochaihu Tang (Minor Radix Bupleuri Decoction) and Radix scutellariae extract. Thus, a specific LC-MS method was developed and validated for the determination of these flavonoids in the plasma of rats after oral administration Xiaochaihu Tang and Radix scutellariae extract. Chromatographic separation was performed on a Zorbax SB C(18) column (150mmx4.6mm, i.d.: 5microm) with 0.1% formic acid in water and acetonitrile by linear gradient elution. Baicalin, wogonoside and carbamazepine (internal standard, I.S.) were detected in select-ion-monitoring (SIM) mode with a positive electrospray ionization (ESI) interface. The following ions: m/z 447 for baicalin, m/z 461 for wogonoside and m/z 237 for the I.S. were used for quantitative determination. The calibration curves were linear over the concentration ranges from 0.1231 to 6.156microg mL(-1) for baicalin and 0.08832 to 4.416microg mL(-1) for wogonoside. The lower limit of detection (LLOD) based on a signal-to-noise ratio of 2 was 0.06155microg mL(-1) for baicalin and 0.04416microg mL(-1) for wogonoside. Intra-day and inter-day precisions (RSD%) were within 10% and accuracy (RE%) ranged from -6.4 to 4.4%. The extraction recovery at three QC concentrations ranged from 74.7 to 86.0% for baicalin and from 71.3 to 83.7% for wogonoside. The plasma concentrations of baicalin and wogonoside in rats at designated time periods after oral administration were successfully determined using the validated method, pharmacokinetic parameters were estimated by a non-compartment model. Following oral administration of Xiaochaihu Tang and Radix scutellariae extract, the t(1/2) of baicalin was 3.60+/-0.90 and 5.64+/-1.67, the C(max1) was 1.64+/-0.99 and 5.66+/-2.02, the t(max1) was 0.13+/-0.05 and 0.20+/-0.07, the C(max2) was 2.43+/-0.46 and 3.18+/-1.66, and the t(max2) were 6.40+/-1.67 and 5.66+/-2.02, respectively. Following oral administration of Xiaochaihu Tang and Radix scutellariae extract, the t(1/2) of wogonoside was 4.97+/-1.68 and 7.71+/-1.55, the C(max1) was 1.39+/-0.83 and 1.45+/-0.37, the t(max1) was 0.21+/-0.20 and 0.17+/-0.01, the C(max2) was 1.90+/-0.55 and 1.42+/-0.70, and the t(max2) was 5.60+/-1.67 and 5.20+/-1.79, respectively. A significant difference (p<0.05) was observed for t(1/2), and the elimination of baicalin and wogonoside in Xiaochaihu Tang was increased.