Complex formation of an estrone-salicylaldehyde semicarbazone hybrid with copper(II) and gallium(III): Solution equilibria and biological activity

The solution chemical properties such as proton dissociation, complex formation with copper(II) and gallium(III) ions in addition to antibacterial and antitumor activity of a novel tridentate salicyaldehyde semicarbazoneestrone hybrid (estrone-SC) and a related bicyclic compound (thn-SC) were investigated. The crystal structure of complex [Cu(thn-SCH- 1)Cl] was studied by single crystal X-ray diffraction method. Estrone-SC and thnSC form mono-ligand complexes with Cu(II) characterized by relatively high stability, however, they are much less stable than their thiosemicarbazone analogues. The neutral Cu(II) complexes with (O-,N,O- )(H2O) coordination mode predominate at physiological pH. Estrone-SC and thn-SC are more efficient Ga(III) binders in comparison with thiosemicarbazones, although the complexes also suffer dissociation at pH 7.4. The Cu(II) complex of estrone-SC displayed significant cytotoxicity in A549, SW480 and CH1/PA cancer cells, and moderate apoptosis induction and ROS formation. The semicarbazone compounds did not exhibit antibacterial effect; unlike the related Cu(II)-thiosemicarbazone complexes represented by the fairly low MIC values (3-50 mu M) obtained on the Gram-positive Staphylococcus aureus and Enterococcus faecalis bacteria.

Automated summary

The study investigated the solution chemical properties and biological activities of a novel tridentate salicyaldehyde semicarbazoneestrone hybrid and a related bicyclic compound. The compounds showed relatively high stability, efficient gallium binding, significant cytotoxicity against cancer cells, and dissociation at physiological pH.