Issue 38, 2018

New gold pincer-type complexes: synthesis, characterization, DNA binding studies and cytotoxicity

Abstract

With the aim of assessing whether Au(III) compounds with pincer type ligands might be utilized as potential antitumor agents, three new monofunctional Au(III) complexes of the general formula [Au(NN’N)Cl]Cl2, where NN’N = 2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)pyridine (H2LtBu, 1), 2,6-bis(5-tert-butyl-1-methyl-1H-pyrazol-3-yl)pyridine (Me2LtBu, 2) or 2,6-bis((4S,7R)-1,7,8,8-tetramethyl-4,5,6,7-tetrahydro-1H-4,7-methanoindazol-3-yl)pyridine (Me2*L, 3) were synthesized. All complexes were characterized by elemental analysis, spectroscopic techniques (IR, UV-Vis, 1D and 2D NMR) and mass spectrometry (MALDI TOF MS). The chemical behavior of the complexes under physiological conditions was studied by UV-Vis spectroscopy, which showed that all compounds were remarkably stable and that the gold center remained in the 3+ oxidation state. The kinetics and the mechanism of the reaction of complexes 1–3 with guanine derivatives (i.e. guanosine (Guo) and guanosine-5′-monophosphate (5′-GMP)) and calf thymus DNA (CT DNA) were studied by stopped-flow spectroscopy. The three complexes displayed moderately different rate constants in their reactions with Guo, 5′-GMP and CT DNA, which can be explained by the steric hindrance and σ-donicity of the methyl substituent on the bis-pyrazolylpyridine fragment in complexes 2 and 3. The measured enthalpies and entropies of activation (ΔH > 0, ΔS < 0) supported an associative mechanism for the substitution process. The interaction of the newly synthesized complexes 1–3 with CT DNA was investigated by UV-Vis and fluorescence spectroscopy, and also by viscosity measurements, which all indicated that complexes 1–3 bound to CT DNA with moderate binding affinity (Kb = 1.6–5.7 × 103 M−1) and stabilized the duplex of CT DNA. Molecular docking indicated that complexes 1–3 interacted with DNA via intercalation. Complex 1 reduced the cell survival of all the investigated cell lines (A549, A375, and LS-174) with IC50 values being up to 20 μM. We have shown that 1 induced perturbations of the cell cycle and led to apoptosis in human melanoma A375 cells. Complex 1 also affected the level of reactive oxygen species (ROS) in the same cells. However, pre-treatment of A375 cells with NAC (ROS scavenger) reversed the effect of 1 on their survival.

Graphical abstract: New gold pincer-type complexes: synthesis, characterization, DNA binding studies and cytotoxicity

Supplementary files

Article information

Article type
Paper
Submitted
17 Jul 2018
Accepted
30 Aug 2018
First published
31 Aug 2018

Dalton Trans., 2018,47, 13696-13712

New gold pincer-type complexes: synthesis, characterization, DNA binding studies and cytotoxicity

S. Radisavljević, I. Bratsos, A. Scheurer, J. Korzekwa, R. Masnikosa, A. Tot, N. Gligorijević, S. Radulović and A. Rilak Simović, Dalton Trans., 2018, 47, 13696 DOI: 10.1039/C8DT02903B

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements