Synthesis and evaluation of pyrazole-fused quinoline hybrids as dual-function anticancer and fluorescent live-cell imaging agents.

This study reports the synthesis and biological evaluation of pyrazole-fused quinolines (2a1-2a5) as potential anticancer agents targeting human DNA topoisomerases. Owing to their intrinsic fluorescence, the synthesized compounds were also explored for live-cell imaging applications. The synthetic strategy involved a multistep sequence comprising Claisen-Schmidt condensation, cyclocondensation, oxidation, reduction, and final ring annulation. In vitro biological evaluation identified compounds 2a4, 2a1 and 2a5 as the most active derivatives against MDA-MB-231 breast cancer cells, with IC₅₀ values of 6.91 ± 0.21, 8.55 ± 0.18 and 9.59 ± 0.47 μM, respectively. Enzymatic topoisomerase inhibition studies suggested that the synthesized series exhibits dual Topo I/II inhibitory potential, with compound 2a4 showing the most favorable inhibition profile and the highest antiproliferative activity against MDA-MB-231 cells. Further biological investigation indicated that compound 2a4 increased intracellular reactive oxygen species (ROS) levels and induced G2/M phase cell-cycle arrest. Computational analyses, including molecular docking and molecular dynamics simulations, suggested stable ligand-enzyme interactions, while MM-GBSA calculations provided comparative insights into the binding trends. In silico ADME prediction suggested that compound 2a4 possesses favorable drug-like characteristics, including acceptable oral absorption and limited blood-brain barrier permeability. Confocal microscopy revealed the intrinsic fluorescence of compound 2a1 and supported its fluorescence-based cellular imaging applications. Overall, compounds 2a4 and 2a1 represent promising in vitro leads for further investigation as topoisomerase-targeting anticancer scaffolds with fluorescence imaging capability.