DNA binding properties and cell viabilities of metal complexes derived from (E)-2-hydroxy-N'-((thiophen-2-yl)methylene)benzohydrazone and (E)-N'-((thiophen-2-yl)methylene)isonicotinylhydrazone.

Objective: This study aims to investigate the CT-DNA (Calf thymus DNA) binding properties and HeLa cell viabilities of metal complexes derived from (E)-2-hydroxy-N'-((thiophen-2-yl)methylene)benzohydrazone (H2L1) and (E)-N'-((thiophen-2-yl)methylene)isonicotinylhydrazone (HL2).

Materials And Methods: A series of metal complexes derived from (E)-2-hydroxy-N'-((thiophen-2-yl)methylene)benzohydrazone (H2L1) and (E)-N'-((thiophen-2-yl)methylene)isonicotinylhydrazonewere (HL2) were synthesized, and their structures were characterized through FT-IR, ESI-MS, elemental analysis, molar conductivities and X-ray diffraction. DNA binding properties between CT-DNA and metal complexes were investigated by UV-Vis spectrophotometry and viscosity titration. The toxicological properties of compounds on HeLa cell were measured in vitro.

Results: Ligand H2L1 or HL2 exhibits a tridentate and anion ligand and uses oxygen anion, nitrogen atom and sulfur atom to coordinate with metal ions. When coordinated with metal ions, the unit O=C-NH- of each ligand has been enolized and deprotonated into -O-C=N-. The suggested chemical formulas of metal complexes are: [Co(HL1)2], [Ni(HL1)2], [Cu(HL1)2], [Co(L2)2], [Cu(L2)2], [Zn(L2)2], [ScL2(NO3)2(H2O)2], [Pr(L2)2(NO3)] and [Dy(L2)2(NO3)]. Both ligands and their metal complexes can bind strongly to CT-DNA through hydrogen bond and intercalation with Kb of 104~105 L mol-1 compared to ethidium bromide [classical DNA intercalator, Kb(EB-DNA) = 3.068 × 104 L mol-1]; however, the groove pattern cannot be excluded. The coexistence of multiple binding modes may be a common form of drug binding to DNA. HeLa cell shows lower viabilities in the presence of [Ni(HL1)2] and [Cu(HL1)2] (*p < 0.05) compared to the other compounds, with the LC50 of 2.6 μmol L-1 and 2.2 μmol L-1, respectively.

Conclusions: These compounds, especially [Ni(HL1)2] and [Cu(HL1)2], will be promising for anti-tumor drugs, which should be further studied.