Mixed-Ligand Cu(II)-Vanillin Schiff Base Complexes; Effect of Coligands on their DNA Binding, DNA Cleavage, SOD Mimetic and Anticancer Activity

SOD mimics with varying coligand are momentous in developing potential chemotherapeutic drugs. Cu(II) based SOD mimics 1-4 [CuLH(OAc)(H2O)Y)] (LH=2-((E)-(1,3-dihydroxy-2-methylpropan-2-ylimino)methyl)-6-methoxyphenol, OAc = CH3COO, 1: Y = H2O; 2: Y= phen (1,10-phenanthroline), 3: Y = tpimH (2,4,5-triphenylimidazole); 4: Y= tfbimH (2-(trifluoromethyl)benzimidazole) were synthesized and thoroughly characterized. Their interaction with CT-DNA showed different non-covalent binding behaviour. SOD activity of 2 was highest among 1-4 which was further validated by gel electrophoresis. The pBR322 plasmid strand break offered by 2+O2.− system reveals oxidative cleavage mechanism. In vitro antimicrobial activity of 1-4 was shown by percent inhibition data while in vitro anticancer activity of 1-4 was screened using 16 human carcinoma cell lines of different histological origin. Complex 2 showed higher efficacy towards 14 cell lines. Nitrogen-donar-bridged Cu(II) binding site with distorted square pyramidal geometry are absolutely essential for SOD activity. Oxidation by O2•- to give H2O2 is a proton-coupled electron transfer followed by outer or inner sphere pathway . ⺠1-4 exhibit novel structure because of active sites that mimics native SOD enzyme. ⺠Complexes with free -OH pertains to guanidinium group of Arg residue of native SOD. ⺠nitrogen containing heterocyclic units act as substitute for His residues. ⺠distorted structure around Cu(II) is feasibile for the attack of O2-.