Development and Validation of a Rapid and Simple UPLC–ESI–MS Method for Pharmacokinetics and Tissue Distribution of Astragaloside III in Rats

A rapid and simple ultra-performance liquid chromatography-electrospray ionization-mass spectrometry (UPLC-ESI-MS) method for the determination of astragaloside III was developed and used in a pharmacokinetic and tissue distribution study in rats following the oral administration 95% ethanol extraction of Zhenqi Fuzheng capsules. Although astragaloside III and astragaloside IV have the same molecular weight and very similar structures, they were successfully separated using this method. Quantification was performed using low-energy collision tandem mass spectrometry (CID-MS-MS) with the multiple reaction monitoring scan mode of the following precursor ion. product ion at m/z 807.61 -> 335.22 for astragaloside III and at m/z 633.18 -> 331.18 for the internal standard (hesperidin). Both astragaloside III and astragaloside IV in rat plasma were best fit to a two-compartment model. The tissue distribution study showed the overall trend of disposition of astragaloside III were C-thymus > C-spleen > C-stomach > C-liver > C-heart > C-kidney > C-lung > C-testicle. The high levels of astragaloside III in thymus and spleen indicated an accumulation in organs involved in immune responses and showed that these organs are major target sites in vivo. The results in the article will provide valuable information for use in clinical applications of astragaloside III.