New copper (II) complexes bearing tryptophan‐based Schiff bases and 2,2′‐bipyridine: Crystal structures, DNA/BSA interactions and antiproliferative activities

Abstract

Abstract[Cu(5‐ClSal‐Trp)(bpy)]·CH3OH (1) and [Cu(3,5‐ClSal‐Trp)(bpy)]·H2O (2) (5‐ClSal‐Trp: Schiff base derived from 5‐chlorosalicylaldehyde and tryptophan, 3,5‐ClSal‐Trp: Schiff base derived from 3,5‐dichlorosalicylaldehyde and tryptophan, bpy: 2,2′‐bipyridine) have been synthesized and analyzed by CHN analysis, FTIR, electronic absorption spectroscopy, ESI‐MS and XRD techniques. Interaction of the complexes with biomolecules {calf thymus DNA (CT‐DNA) and bovine serum albumin (BSA)} has been researched by fluorescence and electronic absorption spectroscopy. The results show that the complexes can bind via a moderate intercalation binding mode. According to the results obtained with both methods, the logKb and logKSV values of the complexes were found to be very close to each other. BSA quenching mechanism was found to be static. The results showed that the interaction between the complexes and BSA is driven by the hydrogen bond and van der Waals interaction. Additionally, the r values of the complexes (the complex 1 = 0.59 nm and the complex 2 = 0.53 nm) calculated from FRET theory suggested that the distance between the complexes (acceptor) and BSA (donor) is quite close. The complexes exhibited free radical scavenging activity compared to the standard antioxidant β‐carotene and catechin. Antiproliferative efficiency of the complexes on both breast cancer cells (MCF‐7 and MDA‐MB‐231) were also researched using the Sulforhodamine B (SRB) viability assay. It was found that the complex 1 (IC50 = 10.99 μM) exhibited higher cytotoxicity than cisplatin (IC50 = 15.6 μM) against MDA‐MB‐231 cell line. Additionally, intracellular reactive oxygen species (ROS) formation was determined by dihydroethidium (DHE) fluorescent staining. N‐acetylcysteine (NAC) was used as an efficient reactive oxygen species (ROS) scavenger. It was observed that newly synthesized Cu (II) complexes exhibited anti‐growth potential in human breast cancer cells. Additionally, it was determined that the complexes induced reactive oxygen species (ROS) formation in cells in a dose‐dependent manner.