| Summary: | Four 1,10-phenanthroline derivatives (<b>1</b>–<b>4</b>) were synthesized as potential telomeric DNA binders, three substituted in their chains with thiosemicarbazones (TSCs) and one 4-phenylthiazole derivative. The compounds were characterized using NMR, HRMS, FTIR-spectroscopy and combustion elemental analysis. Quadruplex and dsDNA interactions were preliminarily studied, especially for neutral derivative <b>1</b>, using FRET-based DNA melting assays, equilibrium dialysis (both competitive and non-competitive), circular dichroism and viscosity titrations. The TSC derivatives bind and stabilize the telomeric Tel22 quadruplex more efficiently than dsDNA, with an estimated 24-fold selectivity determined through equilibrium dialysis for compound <b>1</b>. In addition, cytotoxic activity against various tumor cells (PC-3, DU145, HeLa, MCF-7 and HT29) and two normal cell lines (HFF-1 and RWPE-1) was evaluated. Except for the 4-phenylthiazole derivative, which was inactive, the compounds showed moderate cytotoxic properties, with the salts displaying lower IC<sub>50</sub> values (30–80 μM), compared to the neutral TSC, except in PC-3 cells (IC<sub>50</sub> (<b>1</b>) = 18 μM). However, the neutral derivative was the only compound that exhibited a modest selectivity in the case of prostate cells (tumor PC-3 versus healthy RWPE-1). Cell cycle analysis and Annexin V/PI assays revealed that the compounds can produce cell death by apoptosis, an effect that has proven to be similar to that demonstrated by other known 1,10-phenanthroline G4 ligands endowed with antitumor properties, such as PhenDC3 and PhenQE8.
|
|---|