Antithrombotic And Antiplatelet Activity Of An Organometallic Rhodium(I) Complex Incorporating A Substituted Thieno-[2,3-D]-Pyrimidine Ligand: Synthesis, Structural Characterization, And Molecular Docking Calculations

The antiplatelet and antithrombotic activity of a novel organometallic rhodium(I) complex of the formula [Rh(cod)Cl(tpc)] (1) (cod = cis-1,5-cyclooctadiene; tpc = methyl 2-amino-4-(diethylamino)-thieno-[2,3-d]-pyrimidine-6-carboxylate) was investigated. Complex 1 was easily synthesized by a one-pot, high-yield reaction and was fully characterized by standard spectroscopic techniques including FT-IR, UV-Vis, and NMR spectroscopy and by elemental analysis. The molecular structures of tpc and 1 were determined by single-crystal X-ray crystallography. Complex 1 displayed a slightly distorted square planar geometry and is the first crystallographically characterized example of a coordination compound bearing the ligand precursor tpc. Biological studies demonstrate that 1 displays strong antiplatelet and antithrombotic properties in vitro, by inhibiting both the aggregation of human and washed rabbit platelets induced by the potent inflammatory and thrombotic mediator, platelet-activating factor (PAF) in the micromolar range. This is an approach of continuous interest in the field. Molecular docking calculations suggest that 1 can fit at the ligand-binding site of the PAF receptor (PAFR) and thus block PAF thrombotic activities, through an antagonistic effect on the PAF/PAFR-related pathway, which is in accord with the experimental findings. Complex 1 constitutes an interesting example of a metal-based PAF inhibitor with promising antiplatelet, antithrombotic, and anti-inflammatory activity, because PAF is the most potent inflammatory lipid mediator. This is also supported by the fact that 1 is an inhibitor of other inflammatory and thrombotic mediators like thrombin, along with well-established platelet agonists like ADP and collagen.