New bioactive zinc(II) complexes with peptides and their derivatives: Synthesis, structure, and in vitro insulinomimetic activity

Four Zn(II) complexes with dipeptides and three new Zn(II) complexes with pseudo-tripeptides were prepared and a complex, [Zn(glythr)(2)](n), was revealed to have a polymeric structure by X-ray structure analysis. The ligand, glythr, acts as a bridging ligand completely, a monodentate oxygen atom of the terminal carboxyl group of threonine residue and a didentate ligand containing the nitrogen and oxygen atoms of glycine one. Because the Zn2+ ion has a distorted six-coordinated octahedral geometry, it binds with two terminal carboxyl groups and two didentate ligands. Also, all Zn(II) complexes were found to have high in vitro insulinomimetic activity compared with that of zinc sulfate, as estimated by the inhibition of free fatty acid release in isolated rat adipocytes that had been treated with epinephrine (adrenalin).