Comparative pharmacokinetics of timosaponin B-II and timosaponin A-III after oral administration of Zhimu-Baihe herb-pair, Zhimu extract, free timosaponin B-II and free timosaponin A-III to rats

The aim of this study was to compare the pharmacokinetics of timosaponin B-II and timosaponin A-III in rat plasma after oral administration of Zhimu-Baihe herb-pair, Zhimu extract, free timosaponin B-II and free timosaponin A-Ill. After addition of internal standard (IS) ginsenoside Rh1, plasma samples were pretreated by protein precipitation. Chromatographic separation was carried out on a SHISEIDO CAP-CELL PAK C-18 column (100 mm x 3 mm i.d., 3.0 mu m) with the mobile phase consisting of acetonitrile and 0.05% (v/v) formic acid by linear gradient elution. The detection was performed on an Agilent G1946D single quadrupole mass spectrometer with negative electrospray ionization (ESI) interface in select-ion-monitoring (SIM) mode. The following ions: m/z 919 for timosaponin B-II, m/z 739 for timosaponin A-III and m/z 683 for the IS were used for quantitative determination. Good linearity was achieved over the concentration ranged from 4.0-793.3 ng/mL to 3.9-781.3 ng/mL for the two saponins. The precision of the in vivo study was evaluated by intra- and inter-day assays and the percentages of relative standard deviation were all within 15%. The plasma concentrations of timosaponin B-II and timosaponin A-Ill in rats at designated time periods were successfully determined using this fully validated method, and statistically significant differences (p <0.5) in pharmacokinetic parameters including AUC(0-t), AUC(0-infinity) and MRT (mean residence time) were obtained. Compared to these pharmacokinetic parameters after oral administration of Zhimu extract and monomer solution, higher peak concentration (C-max is higher), slower elimination (MRT is longer) and larger AUC values could be observed after giving Zhimu-Baihe herb-pair in our study. Therefore, this result not only elucidated the steady and long-lasting pharmacological properties but also revealed the practical value of the compatibility of herb-pair remedy. (C) 2013 Elsevier B.V. All rights reserved.