Palladium(II) and ruthenium(II) complexes of benzotriazole functionalized N-heterocyclic carbenes: Cytotoxicity, antimicrobial, and DNA interaction studies

In the present study, four palladium and four ruthenium complexes were synthesized with benzotriazole substituted N-heterocyclic carbene ligands. The structures of complexes were established by appropriate spectroscopic methods and elemental analyses. In addition, the crystal structure of a Pd-NHC complex (1c) was reported. Anticancer, antimicrobial and DNA interaction properties of the complexes were examined. Antimicrobial effects of the complexes were tested against two bacteria strains and one fungi strain. Cytotoxic effects of the complexes were tested against human breast (MCF-7) and colorectal (Caco-2) cancer cell lines and non-cancer mouse fibroblast (L-929) cell lines. Ruthenium complexes were found as more cytotoxic than palladium complexes against cancer cell lines. Especially, benzyl containing, benzimidazole-based ruthenium complexes (3c and 3d) were found as non-cytotoxic against non-cancer L-929 cell lines while performing comparable cytotoxicity against Caco-2 cancer cell lines with cisplatin. In addition, DNA interaction studies were performed with pBR322 plasmid DNA and ctDNA and results showed that both palladium and ruthenium complexes have weaker ability to interact with DNA than cisplatin. The results from this study showed that although the cytotoxic properties of the complexes are not stronger than cisplatin, selectivity of benzyl containing benzimidazole-based ruthenium-NHC complexes against Caco-2 cell lines provides them an advantage, and they deserve further research in the treatment of human colorectal cancer. (c) 2019 Elsevier B.V. All rights reserved.