Synthesis, characterization and antitumor studies of transition metal complexes of o-hydroxydithiobenzoate

Abstract

o-Hydroxydithiobenzoate (o-HOdtb) forms complexes, [Ni(o-HOdtb)(o-HOdtbS)], [Cu(o-Odtb)], [Co(o-HOdtb)3], [Fe2(o-Odtb)3], [Bun4N][V(o-Odtb)3] and [Bun4N][Zn(o-HOdtb)3] which were characterized by analyses and physicochemical studies. The bonding sites of o-HOdtb and the geometry of the complexes were determined by magnetic susceptibility, IR, ESR, NMR, Mössbauer and electronic spectral data. The structure of [Bun4N][Zn(o-HOdtb)3] and H2C(o-HOdtb)2 were assigned by single crystal X-ray diffraction studies. The monomeric complex [Bun4N][Zn(o-HOdtb)3] crystallizes in Pna21 space group. The Mössbauer spectra of [Fe2(o-Odtb)3] at 298 and 80K suggest the presence of high spin iron(III) with an S=5/2 state. All the metal complexes were observed to inhibit the growth of tumor in vitro, whereas, ligand did not. In vivo administration of these complexes resulted in prolongation of survival of tumor-bearing mice. Tumor bearing mice administered with metal complexes showed reversal of tumor growth associated induction of apoptosis in lymphocytes. The paper discusses the possible mechanisms and therapeutic implication of the ligand and its metal complexes in tumor regression and tumor growth associated immunosuppression.