Novel 2-aminopyridine liganded Pd(II) N-heterocyclic carbene complexes: Synthesis, characterization, crystal structure and bioactivity properties

In this work, the synthesis, crystal structure, characterization, and enzyme inhibition effects of the novel a series of 2-aminopyridine liganded Pd(II) N-heterocyclic carbene (NHC) complexes were examined. These complexes of the Pd-based were synthesized from PEPPSI complexes and 2-aminopyridine. The novel complexes were characterized by using C-13 NMR, H-1 NMR, elemental analysis, and FTIR spectroscopy techniques. Also, crystal structures of the two compounds were recorded by using single-crystal X-ray diffraction assay. Also, these complexes were tested toward some metabolic enzymes like a-glycosidase, aldose reductase, butyrylcholinesterase, acetylcholinesterase enzymes, and carbonic anhydrase I, and II isoforms. The novel 2-aminopyridine liganded (NHC) PdI2(2-aminopyridine) complexes (1a-i) showed Ki values of in range of 5.78 +/- 0.33-22.51 +/- 8.59 nM against hCA I, 13.77 +/- 2.21-30.81 +/- 4.87 nM against hCA II, 0.44 +/- 0.08-1.87 +/- 0.11 nM against AChE and 3.25 +/- 0.34-12.89 +/- 4.77 nM against BChE. Additionally, we studied the inhibition effect of these derivatives on aldose reductase and alpha-glycosidase enzymes. For these compounds, compound 1d showed maximum inhibition effect against AR with a Ki value of 360.37 +/- 55.82 nM. Finally, all compounds were tested for the inhibition of alpha-glycosidase enzyme, which recorded efficient inhibition profiles with Ki values in the range of 4.44 +/- 0.65-12.67 +/- 2.50 nM against aglycosidase.