Pharmacokinetic and tissue distribution study of six saponins in the rat after oral administration of Ilex pubescens extract using a validated simultaneous UPLC-qTOF-MS/MS assay

Ilex pubescens Hook. et Arn is a medicinal plant of the Ilex family that is mainly used for the treatment of cardiovascular diseases. Its main medicinal ingredients are total triterpenoid saponins (IPTS). However, the pharmacokinetics and tissue distribution of the main multi-triterpenoid saponins are lacking. This is the first report that demonstrates a sensitive ultra-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UPLC-qTOF-MS/MS) method for the quantification of ilexgenin A (C1), ilexsaponin A1 (C2), ilexsaponin B1 (C3), ilexsaponin B2 (C4), ilexsaponin B3 (DC1) and ilexoside O (DC2) in rat plasma and various tissues of the heart, liver, spleen, lungs, kidney, brain, stomach, duodenum, jejunum, ileum, colon and thoracic aorta. The chromatographic separation was carried out on an Acquity HSS T3 UPLC column (2.1 × 100 mm, 1.8 µm, Waters, USA) with a mobile phase consisting of 0.1% (v/v) formic acid (A) and acetonitrile containing 0.1% (v/v) formic acid (B) at a flow rate of 0.25 mL/min. The MS/MS detection was performed by electrospray ionization (ESI) using selected ion monitoring (SIM) in negative scan mode. The developed quantification method showed good linearity over the concentration range of 10-2000 ng/mL for plasma and 25-5000 ng/mL for tissue homogenates with R2 ≥ 0.990. Lower limits of quantification (LLOQ) was 10 ng/mL in plasma and 25 ng/mL in tissue homogenates. The intra- and inter-day precision were less than 10.39%, and the accuracy was between - 1.03% and 9.13%. The extract recoveries, dilution integrity and matrix effect were well within satisfactory limits. Using the validated method, the pharmacokinetic parameters, including half-life, AUC, Cmax, CL, and MRT, of six triterpenoid saponins in rats after oral administration were provided by establishing their plasma concentration-time curves, while their absolute quantification in various tissues after oral administration was also determined at first, which provides a scientific basis for their clinical application.