Triphenylphosphonium-triazole hybrids as mitochondria-targeted anticancer agents: design, DNA binding, cytotoxicity...

In this study, three novel triphenylphosphonium-containing 1,2,3-triazole derivatives (7-9) were synthesized and structurally characterized by FT-IR, ¹H NMR, and elemental analysis. DNA binding properties were investigated by UV-Vis titration and fluorescence competitive displacement experiments. Spectral changes, including hypochromic and hyperchromic effects, showed a strong affinity towards FSds-DNA, with binding constants on the order of 10⁵ M^-1. Fluorescence quenching studies using ethidium bromide and Hoechst 33258 revealed effective probe displacement with higher Stern-Volmer constants for the Hoechst system, suggesting a preferential minor groove binding mode. Lipophilicity assessment (Log P = 1.60-2.05) showed that para-substitution significantly altered hydrophobicity while preserving drug-like properties. Biological evaluation demonstrated potent antiproliferative activity against lung (A549, Calu-1, H1650) and bone (Saos-2) cancer cell lines and exhibited lower GI₅₀ values (∼1 µg mL^-1) compared to 5-fluorouracil (5FU). Compounds containing electron-attracting substituents (7 and 9) exhibited enhanced cytotoxicity, moderate TGI and LC₅₀ values, and improved tumor selectivity indices (TSI = 1.97 and 2.78, respectively) while maintaining low toxicity against normal cells. LDH assays confirmed limited membrane damage (<20%) at TGI concentrations, and fluorescence microscopy (DAPI, Rhodamine-123, Hoechst/PI) demonstrated mitochondrial membrane depolarization and apoptosis induction, particularly for compounds 7 and 9. Overall, the results highlight that modulation of para-substituents critically influences DNA interaction, lipophilicity, mitochondrial targeting, and anticancer activity. These triphenylphosphonium-triazole derivatives represent promising mitochondria-targeted anticancer candidates for further optimization. The binding affinity and interaction modes of compound 9, which showed the highest inhibitory activity in both DNA-binding and anticancer assays, were elucidated via molecular docking studies.