Transition metal coordination compounds of an antiobesity serotoninergic ligand: spectroscopic characterization and adipogenesis activity

Coordination compounds of cobalt(II), nickel(II), copper(II) and zinc(II) with L-5-hydroxytryptophan (L-5-HTP) were synthesized and characterized by elemental analysis, IR and UV–Vis-NIR spectroscopy, mass spectrometry and thermogravimetric analysis. The X-ray structure of the pure enantiomer ligand (L-5-HTP) was obtained. The ligand coordinates to the metal ions in an unidentate mode, where the donor atom is the oxygen from the carboxylic group. The intramolecular H-bond, N1H···O2, observed in the X-ray crystal structure of the free L-5-HTP, remains as a stabilization factor in all of the coordination compounds. Two types of geometries were adopted by the metal centers: tetrahedral and octahedral. In vitro antiadipogenic studies of the coordination compounds showed that the tetrahedral cobalt(II) and copper(II) complexes presented potential antiobesity properties.