Pharmacokinetics and oral bioavailability studies of three saikogenins in rats using a validated UFLC-MS/MS method.

Radix Bupleuri (RB) has been widely used in Traditional Chinese Medicine with a long history. Saikosaponins (SSs), the major constituents of RB, are assumed to be transformed into saikogenins (SGs) by human intestinal microflora prior to absorption and then exert pharmacological effects. There have been detailed reports on the deglycosylation of SSs in the gastrointestinal tract. But to date, there is very limited research addressing the further absorption, distribution, metabolism, and excretion of these deglycosylated derivatives in vivo. In this study, a rapid UFLC-MS/MS method was established and fully validated for simultaneously determining four SGs (SGF, SGA, SGD, and SGG) in rat plasma. The developed method was successfully applied to the pharmacokinetics of three SGs (SGF, SGD, and SGG) in rats after oral and intravenous administrations. Finally, the absolute bioavailabilities were calculated at 0.71% for SGF and 0.66% for SGD. However, the oral bioavailability of SGG was not obtained due to the extremely poor absorption in rats.