Cytotoxic activity of cerium complexes with coumarin derivatives. Molecular modeling of the ligands

Cerium complexes of Umbellipherone, Mendiaxon, Warfarin, Coumachlor. and Ni ffcoumar have been synthesized by reaction of the ligands with cerium nitra te in a stoichiometric ratio of 1:2. The formation of the complexes has bee n proved on the basis of elemental analysis, conductivities, IR spectroscop y, and H-1-NMR spectroscopy. The molecules of the ligands were optimized by means of the semiempirical quantum mechanical method PM3 to the energetica lly most stable conformers. All the ligands were characterized by molecular and submolecular electronic indices and the putative donor centers are pro posed. It is concluded that the lactone- and the keto-carbonyl groups of Wa rfarin, Coumachlor, and Niffcoumar are bonded to the metal ion as bidentate ligands. The other two coumarins are bonded as monodentate ligands. Conduc tivity measurements show the non-electrolytic nature of the complexes. Cyto toxic screening by MTT assay was carried out. The cerium complexes were fou nd to be more active than the inorganic salts.