Search

Abstract: Novel trivalent antimony complexes with the nitrogen donor heterocyclic ligand 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen) or dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq) have been synthesized by the reaction with SbCl3 or PhSbCl2. The crystal structures of [Sb(phen)Cl3] and [PhSb(phen)Cl2]CH3COOH were determined and shown to adopt a distorted square pyramid geometry with a five-coordinated Sb center. Surprisingly, all the complexes, the ligands and PhSbCl2 showed very high antileishmanial activities, with IC50 in the nanomolar range against SbIII-sensitive and -resistant Leishmania infantum (syn. Leishmania chagasi) and Leishmania amazonensis strains. These compounds were much more active against these Leishmania strains than the old trivalent drug potassium antimonyl tartrate. [PhSb(phen)Cl2]CH3COOH complex was found to be the most active compound and the lack of cross-resistance of PhSbCl2 suggests that the transport pathways of this compound across the cell membrane differ from those responsible for the resistance of Leishmania to Sb(OH)3. In the case of the complexes with PhSbCl2, our data supports the model that both ligand and metal contributed to the overall activity of the complex. Furthermore, among the complexes with SbCl3, only bipy showed an improved activity upon complexation. Cytotoxicity evaluations of these compounds against murine peritoneal macrophages showed high selective indexes in the range of 7–70 for [Sb(phen)Cl3], [Sb(bipy)Cl3] and [Sb(dpq)Cl3] complexes, being much more selective than potassium antimonyl tartrate. In conclusion, this study presents a set of new antileishmanial agents including one of the most active Sb-based compounds ever reported, which can contribute to the development of new chemotherapeutic strategies against leishmaniasis including Sb-resistant cases. [Copyright &y& Elsevier]

Five new copper(II) complexes of the type [Cu(N O)(N N)(ClO 4 ) 2 ], in which N O = 4-fluorophenoxyacetic acid hydrazide (4-FH) or 4-nitrobenzoic hydrazide (4-NH) and N N = 1,10-phenanthroline (phen), 4–4′-dimethoxy-2-2′-bipyridine (dmb) or 2,2-bipyridine (bipy) were synthesized and characterized using various spectroscopic methods. The X-ray structural analysis of one representative compound indicates that the geometry around the copper ion is distorted octahedron, in which the ion is coordinated to hydrazide via the terminal nitrogen and the carbonyl oxygen, and to heterocyclic bases via their two nitrogen atoms. Two perchlorate anions occupy the apical positions, completing the coordination sphere. The cytotoxic activity of compounds was investigated in three tumor cell lines (K562, MDA-MB-231 and MCF-7). Concerning K562 cell line, the complexes with 1,10-phenanthroline exhibit high cytotoxic activity and are more active than carboplatin, free ligands and [Cu(phen) 2 ] 2 + . Considering the cytotoxicity results, further investigations for the compounds [Cu(4-FH)(phen)(ClO 4 ) 2 ] I and [Cu(4-NH)(phen)(ClO 4 ) 2 ]∙H 2 O III were performed. Flow cytometric analysis revealed that these complexes induce apoptotic cell death in MDA-MB-231 cell line and bind to DNA with K values of 4.38 × 10 4 and 2.62 × 10 4 , respectively. These compounds were also evaluated against wild type Mycobacterium tuberculosis (ATCC 27294) and exhibited antimycobacterial activity, displayed MIC values lower than those of the corresponding free ligands. [ABSTRACT FROM AUTHOR]

Two new bismuth(III) complexes, [BiL1Cl 2 ] (1) and [BiL2Cl 2 ] (2), in which L1 is (2-hydroxy-4-6-di-tert-butylbenzyl-2-pyridylmethyl)amine and L2 is 2,4-diiodo-6-((pyridine-2-ylmethylamino)methyl)phenol, were synthesized and characterized by elemental and conductivity analyses, atomic absorption spectrometry, infrared and 1H NMR spectroscopies. The molecular structure of 1 reveals that the NN'O ligand forms a 1:1 complex with bismuth through coordination via the nitrogen of the aliphatic amine, the nitrogen of the pyridine ring and the oxygen of the phenolate. The coordination sphere is completed with two chloride anions in a distorted square pyramidal geometry. Bismuth exhibits the same coordination mode in compound 2. The cytotoxic activity of 1 and 2 was investigated in a chronic myelogenous leukemia cell line. The complexes are approximately three times more potent than the corresponding free ligands, with the IC 50 values 0.30 and 0.38 μM for complex 1 and 2 , respectively. To address the cellular mechanisms underlying cell demise, apoptosis was quantified by flow cytometry analysis. From 0.1 μM, both complexes induce apoptosis and there is a remarkable concentration-dependent increase in the population of cells in apoptosis. The complexes were also evaluated against Gram-positive and Gram-negative bacteria. Both inhibited the bacterial growth in a concentration-dependent way, with remarkable activity in some of the tested strains, for example, complex 2 was more active than its free ligand against all bacterial strains and approximately fourteen times more potent against S. dysenteriae and S. typhimurium. Two new Bi(III) complexes with asymmetric [NN'O] ligands were highly cytotoxic to chronic myelogenous leukemia cells, with IC 50 values in the range 0.3–0.4 μmol L−1. Both complexes induce a remarkable concentration-dependent increase in the population of cells in apoptosis. [Display omitted] • Bismuth compounds with asymmetric [NN'O] ligands are cytotoxic to leukemia cells. • Bi(III) binds to an amine N, a pyridine N, a phenolate oxygen, and two chlorides. • Bismuth complexes induce apoptosis in K562 cells at significant low concentrations. • [BiCl 2 (2-hydroxy-4-6-di-tert-butylbenzyl-2-pyridylmethyl)amine] is active vs. S. aureus. • Complex 2 is 14 times as potent as the ligand in S. dysenteriae and S. typhimurium. [ABSTRACT FROM AUTHOR]