Determination of deltonin in rat plasma by using HPLC-MS/MS and the application of this method in pharmacokinetic studies.

Deltonin is a naturally occurring spirostanol glycoside from Dioscorea zingiberensis C.H. Wright, which is used in traditional Chinese medicine. It exerts strong cytotoxic effect on C26 cells, inhibits C26 derived-tumor growth, and prolongs the survival of tumor-bearing mice after its oral administration, indicating its potential for use as an anti-tumor drug. To investigate the pharmacokinetic profiles of deltonin, a rapid, sensitive, and simplified high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) assay was developed and validated for the determination of deltonin in rat plasma. After acetonitrile-mediated plasma protein precipitation, chromatographic separation of deltonin was achieved using a reversed phase Hypersil Gold column (150mm×2.1mm, 5µm), with gradient elution using 0.1% formic acid and acetonitrile. Thereafter, deltonin was quantified using MS/MS with electrospray ionization (ESI) in positive multiple reaction monitoring (MRM) mode. The flow rate of the mobile phase was 200µL/min, and the retention time was 9.03min for deltonin and 6.31min for the internal standard (IS: 20(S)-ginsenoside Rb1). The linear range of the calibration curve was 2-5000ng/mL (r(2)>0.99), and the limit of detection (LOD) was 0.46ng/mL. The intra- and inter-day accuracies ranged from -2.8% to 11.1% and precisions (RSD) were within 13.1%. Deltonin was found to be stable under short-term temperature conditions, post-preparative temperature conditions, and after 3 freeze-thaw cycles conditions. The validated method was successfully applied to a pharmacokinetic study in rats after oral administration of deltonin (50 and 100mg/kg). The pharmacokinetics is characterized by high apparent clearance (CL/F) and apparent volume of distribution (Vd/F).

Pennogenin tetraglycoside stimulates secretion-dependent activation of rat platelets: evidence for critical roles of adenosine diphosphate receptor signal pathways.

BACKGROUND: Total steroidal saponins extracted from the rhizome of Paris polyphylla Sm. var. yunnanensis (TSSPs) have been demonstrated to promote hemostasis in vivo and induce platelet aggregation in vitro. Pennogenin tetraglycoside (Tg) has been identified as one of the active ingredients in TSSPs and can induce rat platelet aggregation. OBJECTIVE: To investigate the functional role of Tg in platelets and the signaling pathway mechanisms which mediate Tg-induced platelet aggregation. METHODS AND RESULTS: Using scanning electron microscopy, the turbidimetric method and flow cytometry, we demonstrated that Tg induces shape change and concentration-dependently induces aggregation, dense granule secretion and a-granule secretion in rat platelets. The activation characteristics were comprehensively confirmed using transmission electron microscopy. Apyrase and antagonists of the platelet adenosine diphosphate (ADP) receptors, P2Y1 and P2Y12, completely inhibited Tg-induced platelet aggregation, which was not sensitive to indomethacin or SQ29548 inhibition. Furthermore, ADP receptor antagonists inhibited Tg-induced a-granule secretion, and blockade of the P2Y1 receptor prevented Tg-induced platelet shape changes. Tg-induced dense granule secretion was not affected by ADP receptor antagonists or various various pharmacological inhibitors of the intracellular effectors involved in dense granule secretion signaling pathways. CONCLUSION: We identified that Tg directly induces platelet activation and demonstrated that Tg-induced platelet activation depends on dense granule secretion of ADP, which in turn activates the P2Y1 and P2Y12 receptor signaling pathways.