Discovery and Characterization of Panaxatriol as a Novel Thrombin Inhibitor from Panax notoginseng Using a Combination of Computational and Experimental Approaches.

Thrombin is a crucial enzyme in the coagulation cascade, and inhibitors of thrombin have been extensively studied as potential antithrombotic agents. The objective of this study was to identify natural inhibitors of thrombin from Panax notoginseng and evaluate their biological activity in vitro and binding characteristics. A combined approach involving molecular docking, thrombin inhibition assays, surface plasmon resonance, and molecular dynamics simulation was utilized to identify natural thrombin inhibitors. The results demonstrated that panaxatriol directly inhibits thrombin, with an IC₅₀ of 10.3 µM. Binding studies using surface plasmon resonance revealed that panaxatriol interacts with thrombin, with a K_D value of 7.8 µM. Molecular dynamics analysis indicated that the thrombin-panaxatriol system reached equilibrium rapidly with minimal fluctuations, and the calculated binding free energy was - 23.8 kcal/mol. The interaction between panaxatriol and thrombin involves the amino acid residues Glu146, Glu192, Gly216, Gly219, Tyr60A, and Trp60D. This interaction provides a mechanistic basis for further optimizing panaxatriol as a thrombin inhibitor. Our study has shown that panaxatriol serves as a direct thrombin inhibitor, laying the groundwork for further research and development of novel thrombin inhibitors.