A new bio-active asymmetric-Schiff base: synthesis and evaluation of calf thymus DNA interaction, topoisomerase IIα inhibition, in vitro antiproliferative activity, SEM analysis and molecular docking studies

Abstract

In this paper, the asymmetric-Schiff base 2-(4-(2-hydroxybenzylideneamino)benzylideneamino)benzoic acid (SB-2) was newly synthesized and characterized by various spectroscopic methods. The interaction of SB-2 with calf thymus DNA was investigated by UV–vis, fluorescence spectroscopy and molecular docking methods. It was determined that SB-2 effectively binds to DNA via the intercalation mode. DNA electrophoretic mobility experiments displayed that topoisomerase IIα could not cleave pBR322 plasmid DNA in the presence of SB-2, confirming that the Schiff base acts as a topo II suppressor. In the molecular docking studies, SB-2 was found to show an affinity for both the DNA-topoisomerase IIα complex and the DNA. In vitro antiproliferative activity of SB-2 was screened against HT-29 (colorectal) and HeLa (cervical) human tumor cell lines by MTT assay. SB-2 diminished the cell viability in a concentration- and incubation time-dependent manner. The ability of SB-2 to measure DNA damage in tumor cells was evaluated with cytokinesis-block micronucleus assay after incubation 24 h and 48 h. Light and scanning electron microscopy experiments of tumor cells demonstrated an incubation time-dependent increase in the proportion of apoptotic cells (nuclear condensation and apoptotic bodies) suggesting that autophagy and apoptosis play a role in the death of cells. Based on the obtained results, it may be considered that SB-2 is a candidate for DNA-targeting antitumor drug.

Communicated by Ramaswamy H. Sarma

GRAPHICAL ABSTRACT

Keywords:

• Schiff bases
• CT-DNA
• topoisomerase II
• molecular docking
• antiproliferative activity
• cytokinesis-block micronucleus assay
• scanning electron microscopy

Acknowledgements

We are thankful to Prof. Dr. Demet Çetin for helping SEM analysis. We are thankful to Dr. Levent Nuralın, Assoc. Prof. Dr. Fatih Akkurt, Prof. Dr. Atilla Murathan for providing the necessary facilities of studying with fluorescence spectrophotometer. We are thankful to Prof. Dr. İlkay Yıldız for helping molecular docking studies.

Disclosure statement

No conflict of interest was declared by the authors.