Syntheses, Structures, and Insulin-like Activities of Oxovanadium(IV) Complexes with Tetra- and Penta-dentate Histidine Derivatives

Abstract

Abstract [VO(pmH)(ClO4)], [VO(HeY)], and [VO((pm)2H)](ClO4) were prepared by reactions of VOSO4 and pmH (N-2-pyridylmethyl-(S)-histidine), HeY (N,N′-ethylene-(S)-histidine-(S)-tyrosine), and (pm)2H (N,N-bis(2-pyridylmethyl)-(S)-histidine), respectively, and followed with Ba(ClO4)2. X-ray structure analysis of [VO(HeY)] showed that a pentadentate ligand and an oxoanion were coordinated with a vanadium(IV) ion, thereby forming a distorted octahedral geometry. In in vitro evaluation using isolated rat adipocytes, a tetradentate complex [VO(pmH)(ClO4)](IC50 = 0.762 mM) was found to be more active at lower concentration than VOSO4 (IC50 = 3.56 mM) in term of IC50 value, a 50% inhibition concentration of FFA release from the adipocytes. On the other hand, two VO complexes of pentadentate (HeY and (pm)2H) ligands were found to be inactive for insulin-like activities.