Study on Absolute Bioavailability of Xanthoceraside in Rat and in Vitro Metabolic Behavior

OBJECTIVE To establish a method to determine the concentration of xanthoceraside(XAN) in rat plasma by LC-MS/MS, and to study its oral absolute bioavailability and metabolic behavior in vitro in rats. METHODS The blood sample was collected at different time points after intragastric administration of XAN at 40 mg·kg^-1 and intravenous administration of XAN at 2 mg·kg^-1. XAN in plasma sample was analyzed by the validated LC-MS/MS. DAS 3.3.2 software was used to calculate relevant pharmacokinetic parameters, the metabolic behavior of XAN was studied by intestinal microflora and liver S9 incubation test in vitro. RESULTS The linear concentration ranges of XAN were 1.56-100 mg·L^-1 and 200-40 000 mg·L^-1, which were applied to the determination after intragastric and intravenous administration separately. The specificity, precision, accuracy, matrix effect, extraction recovery and stability of the methods were consistent with the requirements for biological sample analysis. The pharmacokinetic parameters ρ_max and AUC_0-tafter oral administration were (38.33±33.21)mg·L^-1and (100.77±28.85)mg·h·L^-1, respectively; and the ρ_max and AUC_0-t after intravenous injection were (24 428.01±10 386.18)mg·L^-1 and (17 355.24± 10 498.7)mg·h·L^-1, respectively. The absolute bioavailability of XAN in rat in vitro was 0.028%. In the incubation experiment, XAN remained 90.7% and 99.3% compared with the pre-incubation sample after 48 h of intestinal flora incubation and 2 h of liver S9 incubation. CONCLUSION The LC-MS/MS analytical method established is suitable for the pharmacokinetic study of the XAN in rats. The oral absolute bioavailability of XAN is 0.028%, which might be caused by the low absorption in gastrointestinal tract.