A UPLC-MS/MS method for simultaneous quantification of pairs of oleanene- and ursane-type triterpenoid saponins and their major metabolites in mice plasma and its application to a comparative pharmacokinetic study

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.

Ilexsaponin A1: In vitro metabolites identification and evaluation of inhibitory drug-drug interactions

As a triterpene saponin, ilexsaponin A1 is one of the most abundant, representative and active components in plants of Ilex pubescens, used in the treatment of cardiovascular diseases. This study aimed to identify the metabolites of ilexsaponin A1 and evaluate its in vitro inhibitory drug-drug interaction (DDI) potential by using human liver microsomes (HLM) and cytochrome P450 enzymes (CYPs)-specific probes, with all the qualitative and quantitative analysis performed by LC-MS/MS. As a result, two metabolites generated through the metabolic pathways of glucuronic acid conjugation and glucose conjugation were first time detected in the HLM. An inhibitory DDI evaluating system consisting of 7 major CYP enzymes involving 8 CYP-catalyzed reactions was established, validated and then used for the DDI evaluation. Our data suggested ilexsaponin A1 and its metabolite, ilexgenin A, are not direct or mechanism-based inhibitors of CYP1A2, 2B6, 2C8, 2C9, 2D6, 2E1 or 3A4/5 at 0.05-10 μM. A significant decreased remaining activity of CYP2B6 (from 77.89 % to 23.19 %) was observed in a dose-dependent manner when increased the concentration of ilexsaponin A1 from 50 to 500 μM. Collectively, our data demonstrate ilexsaponin A1 is unlikely to cause DDIs by inhibiting co-administered drugs metabolized by these CYP enzymes.

The combination of Ilexhainanoside D and ilexsaponin A1 reduces liver inflammation and improves intestinal barrier function in mice with high-fat diet-induced non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is becoming a major health concern worldwide. Ilex hainanensis Merr. extract was proved to have anti-inflammation effect on NAFLD, and Ilexhainanoside D (IhD) and ilexsaponin A₁ (IsA) were the main triterpenoid saponins extracted from it.

PURPOSES

To investigate the hepatoprotective effect of the combination of IhD and IsA (IIC) against NAFLD and discuss the potential mechanisms.

METHODS

Male C57BL/6 mice were fed a high-fat diet (HFD) to induce NAFLD and were treated with IIC (60, 120 or 240 mg/kg) for 8 weeks. Growth parameters, abdominal fat content, serum biochemical markers, hepatic lipid accumulation and insulin tolerance were assessed. Quantitative real-time PCR was used to determine the hepatic gene expression of TLR2, TLR4, TNF-α, IL-6, and IL-1β. Western blot analysis was performed to determine the expression of the epidermal tight junction proteins ZO-1 and occludin. Gut microbiota profiles were established via high-throughput sequencing of the V3-V4 region of the bacterial 16S rRNA gene.

RESULTS

IIC significantly reduced the severity of NAFLD induced by HFD in a dose-dependent manner. IIC decreased the ratio of Firmicutes/Bacteroidetes, reduced the relative abundance of Desulfovibrio and increased the relative abundance of Akkermansia. The intestinal barrier was improved as evidenced by the upregulation of the expression of ZO-1 and occludin in the ileum. IIC thus reduced the entry of LPS into the circulation and decreased the hepatic gene expression levels of proinflammatory cytokines.

CONCLUSION

This approach demonstrated the positive effects of IIC in a mouse model of NAFLD, indicating that it possibly acts by reducing inflammation and improving the intestinal barrier function.