Au(III) complexes of symmetrical tetradentate Schiff base ligands: Synthesis, characterization, anticancer/antioxidant potency, in silico prediction, and catalase binding properties

Abstract

Two new gold(III) complexes, [AuL1]Cl3, A, and [AuL2]Cl3, B, were synthesized and characterized. DFT calculations showed square planar geometry for both complexes. Antioxidant results showed that the ability of compounds to inhibit DPPH• is as follows: A > B > L2 > L1. The anticancer assay showed that both complexes have the ability to inhibit the growth of HCT116 colon cancer cell lines, but B shows a relatively better effect than cisplatin. The interaction effects of A and B on the activity and structure of the bovine liver catalase (BLC) were investigated by spectroscopic techniques and molecular docking. Both complexes were able to change the performance and structure of BLC; B has a greater effect on BLC activity, so at concentration of 2 μM, A and B inhibit initial BLC activity by 92.2% and 55.6%, respectively. The interaction mechanism of A and B with BLC was also different; A interacted mostly with van der Waals interactions and hydrogen bonds, but the most important forces for B was hydrophobic interactions. According to docking results, both complexes prefer the domain III of BLC, but B has higher affinity toward BLC than A, which supports the results of spectroscopic and FMO analysis.