# Biological and Teratogenic Evaluations of Nitrogen Heterocycles for Anticancer Therapy

## TL;DR

This study evaluates four nitrogen heterocycles for anticancer potential, finding that the quinoline compound shows strong activity without harming zebrafish embryos.

## Contribution

The study introduces and evaluates four new nitrogen heterocycle derivatives for anticancer therapy, identifying the quinoline compound as a promising candidate.

## Key findings

- The quinoline derivative (3b) showed the strongest DNA intercalation and antitopoisomerase IIα activity.
- All compounds were cytotoxic to breast cancer cells without hemolytic effects on human erythrocytes.
- Zebrafish embryos showed no toxicological effects, but compounds altered antioxidant enzyme activity.

## Abstract

Background: Heterocycle compounds with acridine, quinoline, indole, and pyridine nuclei are potentially active for anticancer activity since they can promote inhibition of vital enzymes, decreasing cell survival after binding to biomolecules. However, unspecific biological interactions can result in unwanted effects, which should be defined during the synthesis and proposition of new molecules. Thus, the objective of this study was to investigate the biological and teratogenic effects of four nitrogen heterocycles proposed for anticancer therapy. Methods: Four 2-cyano-N-phenylacrylamine type derivatives containing acridine (3a), quinoline (3b), indole (3c), and pyridine (3d) nuclei were synthesized and characterized. They were evaluated for their ability to interact with DNA, physicochemical and pharmacokinetic predictions, in vitro and in silico methodologies, besides in vitro inhibition of the Topoisomerase IIα enzyme, antiproliferative activity in tumor and non-tumor cells, hemolytic activity with human erythrocytes, and in vivo toxicological studies with zebrafish embryos. Results: UV–vis absorption studies with ssDNA revealed different spectroscopic effects, with binding constants (Kb) ranging from 1.41 × 105 to 6.46 × 104 M−1. The fluorescence quenching constant (Ksv) with ethidium bromide (EB) varied between 0.53 and 0.67 × 103 M−1. The compounds intercalated into DNA base pairs, a mechanism confirmed by molecular docking, with 3b (quinoline) showing the most substantial interaction. All derivatives exhibited antitopoisomerase IIα activity at 100 μM and were cytotoxic against MCF-7 and T47-D breast tumor cells, particularly against the more aggressive T47-D lineage. No hemolytic activity was observed in human erythrocytes. In vivo assays in zebrafish embryos showed no toxicological or cardiotoxic effects. However, all compounds altered superoxide dismutase (SOD) and catalase (CAT) enzymatic activity, requiring further studies on reactive oxygen species (ROS) generation to assess potential adverse effects. Furthermore, significant results were observed in the physicochemical and pharmacokinetic parameters of the synthesized compounds. Conclusions: The findings highlight the quinoline derivative (3b) as the most promising nitrogen heterocycle due to its antiproliferative activity and biomolecular interactions without adverse effects in zebrafish embryos, distinguishing it from clinically available agents.