Synthesis and distinct urease enzyme inhibitory activities of metal complexes of Schiff-base ligands: Kinetic and thermodynamic parameters evaluation from TG-DTA analysis

Transition metal [Co, Ni, Cu and Zn(II) acetates] complexes of salicylaldehyde derived Schiff bases, 2-{(E)-[(4-chlorophenyl)imino]methyl}phenol (CIMP) and 2-{(E)-[(4-bromophenyl)imino]methyl}phenol (BIMP) were synthesized and characterized by various analytical and spectroscopic studies. The Schiff base ligands and their metal complexes were also screened for their urease, α-chymotrypsin, acetylcholinesterse and butyrylcholinesterase inhibition activities. The ligands were found active against α-chymotrypsin with IC50±S.E.M.=305.0±3.2 and 330.6±1.6μM respectively. The copper complexes of both the ligands were found active in inhibiting urease enzyme with IC50±S.E.M.=10.7±0.2 and 5.0±0.1μM respectively, as compared to standard inhibitor. Structure activity relationship (SAR) was evaluated using autodock programme. It was found that the active complexes block the entrance cavity to the enzyme. All the complexes were evaluated for their thermal degradation studies using TG-DTA analytical methods in static air. Thermodynamic and kinetic parameters were evaluated from the TG/DTA curves using Horowitz–Metzger method.