Novel hydrazone schiff's base derivatives of polyhydroquinoline: synthesis, in vitro prolyl oligopeptidase inhibitory...

This research work reports the synthesis of new derivatives of the hydrazone Schiff bases (1-17) based on polyhydroquinoline nucleus through multistep reactions. HR-ESIMS,¹H- and ¹³C-NMR spectroscopy were used to structurally infer all of the synthesized compounds and lastly evaluated for prolyl oligopeptidase inhibitory activity. All the prepared products displayed good to excellent inhibitory activity when compared with standard z-prolyl-prolinal. Three derivatives 3, 15 and 14 showed excellent inhibition with IC₅₀ values 3.21 ± 0.15 to 5.67 ± 0.18 µM, while the remaining 12 compounds showed significant activity. Docking studies indicated a good correlation with the biochemical potency of compounds estimated in the in-vitro test and showed the potency of compounds 3, 15 and 14. The MD simulation results confirmed the stability of the most potent inhibitors 3, 15 and 14 at 250 ns using the parameters RMSD, RMSF, Rg and number of hydrogen bonds. The RMSD values indicate the stability of the protein backbone in complex with the inhibitors over the simulation time. The RMSF values of the binding site residues indicate that the potent inhibitors contributed to stabilizing these regions of the protein, through formed stable interactions with the protein. The Rg. analysis assesses the overall size and compactness of the complexes. The maintenance of stable hydrogen bonds suggests the existence of favorable binding interactions. SASA analysis suggests that they maintained stable conformations without large-scale exposure to the solvent. These results indicate that the ligand-protein interactions are stable and could be exploited to design new drugs for disease treatment.