Selective Urease Inhibitory and Antimicrobial Activities of Transition Metal Complexes of Amino Acid Bearing Schiff Base Ligand: Thermal Degradation Behavior of Complexes

Amino acid derived Schiff base ligand [1-({[(Z)-(2-hydroxynaphthalen-1-yl)methylidene]-amino}methyl)-cyclohexyl]acetic acid (H-HMAC) and its metal complexes with composition [M(HMAC)(2)] [M = Co(II), Ni(II), Cu(II), and Zn(II)] reported previously were studied for their thermal degradation, antimicrobial and inhibitory activities against the enzymes like urease, alpha-chymotrypsin, acetylcholinesterase and butyrylcholinesterase. Only a zinc-based compound of the zwitter-ion ligand has been found to inhibit the urease activity with IC50= 0.04 +/- 0.01 mu M (value +/- SEM), which is 400 times better than the standard reference drug used. Metal coordination with zinc improved the bioactivity and deserved for selective urease inhibitor development. The inhibitory activity was structurally rationalized by carrying out the molecular modeling studies using AutoDock software. The same metal complex was also observed to inhibit the activity ofCandida albicans. The thermal degradation studies suggest that the order of stability and activation energies of all compounds is as follows: Cu < H-HMAC < Ni < Co = Zn andE*(Zn)>E*(Co)>E*(Ni)>E*(Cu), respectively.