Heloisa Beraldo

Metal complexes of 2-benzoylpyridine-derived thiosemicarbazones: structural, electrochemical and biological studies

Complexes of 2-benzoylpyridine thiosemicarbazone (H2Bz4DH) as well as of its N(4)-methyl (H2Bz4Me) and N(4)-phenyl (H2Bz4Ph) analogues with iron(II), nickel(II) and zinc(II) were characterized by a variety of spectroscopic techniques. Electrochemical studies revealed that the iron(II) complexes undergo oxidation giving the iron(III) analogues, which could be reduced back by cellular thiols such as thioredoxine, suggesting that this process could occur in biological media. The thiosemicarbazones have antifungal activity against Candida albicans that significantly decreases on coordination. The crystal structure 2-benzoylpyridine-N(4)-methyl thiosemicarbazone (H2Bz4Me) was determined.

Gallium(III) complexes of 2-pyridineformamide thiosemicarbazones: Cytotoxic activity against malignant glioblastoma

The gallium(III) complexes [Ga(2Am4DH)(2)]NO(3) (1), [Ga(2Am4Me)(2)]NO(3) (2) and [Ga(2Am4Et)(2)]NO(3) (3) were prepared with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me) and N(4)-ethyl (H2Am4Et) derivatives. The thiosemicarbazones were cytotoxic against malignant RT2 glioblastoma cells (expressing p53 protein) with IC(50) values in the 7.3-360 microM range, and against malignant T98 glioblastoma cells (expressing mutant p53 protein) with IC(50) values in the 3.6-143 microM range. Coordination to gallium strongly increased the cytotoxic potential in complexes 2 and 3, which showed IC(50) values in the 0.81-9.57 microM range against RT2 cells and in the 3.6-11.30 microM range against T98 cells, and were 20-fold more potent than cisplatin. All thiosemicarbazones and gallium complexes were able to induce cell death by apoptosis.

N(4)-tolyl-2-benzoylpyridine thiosemicarbazones and their copper(II) complexes with significant antifungal activity: crystal structure of N(4)-para-tolyl-2-benzoylpyridine thiosemicarbazone

) para os complexos. Nossos resultados sugerem que a coordenacao ao cobre constitui estrategia interessante de reducao da dose necessaria a atividade. Three new copper complexes of general formula [Cu(HL)Cl 2 ] have been obtained with N(4)-ortho (H2Bz4oT, HL1), N(4)-meta (H2Bz4mT, HL2) and N(4)-para-tolyl-2-benzoylpyridine thiosemicarbazone (H2Bz4pT, HL3), in which the thiosemicarbazone attaches to the metal through the N py -N-S chelating system. H2Bz4pT (HL3) crystallizes in the P1 – space group, with a = 9.509(3) A, b = 9.807(4) A, c = 11.564(4) A; α = 100.76(2)°, β = 105.99(2)°, γ = 114.59(2)°. The thiosemicarbazones and their copper(II) complexes exhibit high antifungal activities against Candida albicans with low values of minimum inhibitory concentration (MIC), in the 8-0.3 μg mL -1 (23 – 0.7 μmol L -1 ) range for the free bases and in the 1-0.1 μg mL -1 (2 – 0.3 μmol L -1 ) range for the complexes. Our results suggest that coordination to copper(II) could be an interesting strategy for dose reduction.

Antimony(III) complexes with 2-benzoylpyridine-derived thiosemicarbazones: Cytotoxicity against human leukemia cell lines

The antimony(III) complexes [Sb(2Bz4DH)Cl(2)] (1), [Sb(H2Bz4M)Cl(3)] x 2 H(2)O (2) and [Sb(2Bz4Ph)Cl(2)] (3) were obtained with 2-benzoylpyridine thiosemicarbazone (H2Bz4DH) and its N(4)-methyl (H2Bz4M) and N(4)-phenyl (H2Bz4Ph) derivatives. H2Bz4DH, H2Bz4Ph and complexes (1-3) exhibited high cytotoxic activity against HL-60 and Jurkat human leukemia cell lines. When these compounds were tested against HL-60 cells with ectopic expression of BcrAbl, Bcl-2 or Bcl-X(L), which confer resistance to apoptosis against a variety of death-inducing agents, the cytotoxicity was much lower, indicating apoptosis to be part of their mechanism of action. The cytotoxic activity of complexes 2 and 3 against HL-60 and Jurkat cells was significantly higher than that of the corresponding thiosemicarbazones, suggesting coordination to be an interesting strategy of cytotoxic dose reduction.

2-Acetylpyridine thiosemicarbazones: Cytotoxic activity in nanomolar doses against malignant gliomas

2-acetylpyridine N(4)-phenyl thiosemicarbazone (H2Ac4Ph), and its N(4)-ortho-tolyl (H2Ac4oT), N(4)-meta-tolyl (H2Ac4mT), N(4)-para-tolyl (H2Ac4pT), N(4)-ortho-chlorophenyl (H2Ac4oClPh), N(4)-meta-chlorophenyl (H2Ac4mClPh) and N(4)-para-chlorophenyl (H2Ac4pClPh) derivatives were assayed for their cytotoxicity against RT2 (expressing p53 protein) and against T98 (expressing mutant p53 protein) glioma cells. The compounds were highly cytotoxic against RT2 (IC50=24-1.4 nM) and T98 cells (IC50=50-1.0 nM). IC50 for cisplatin=5 (RT2) and 17 μM (T98). The thiosemicarbazones presented haemolytic activity with IC50>10(-3)M, indicating a very good therapeutic index. SAR studies suggested that stereo properties are critical to define the potential activity of the studied compounds against the RT2 cell line, while electronic properties seem to be important for interaction with the biological target in T98 cells.

Copper(II) and nickel(II) complexes of glyoxaldehyde bis{N(3)-substituted thiosemicarbazones}

Copper(II) and nickel(II) complexes of glyoxaldehyde bis{N(3)-methyl-, bis{N(3)-ethyl-, bis{N(3)-dimethyl-, bis{piperidyl- and bis{hexamethyleneiminylthiosemicarbazone} have been prepared and studied spectroscopically. The five bis(thiosemicarbazones) have been characterized by their melting points, as well as i.r., electronic and 1H-n.m.r. spectra. The four-coordinate copper(II) complexes have been studied by e.s.r. spectroscopy, and the copper(II) and nickel(II) complexes by a number of the spectroscopic techniques mentioned above. Upon formation of these complexes, loss of protons from each thiosemicarbazone moiety occurs, and the bis(thiosemicarbazones) coordinate to the metal centres as dianionic, tetradentate N2S2 ligands.

N4-Phenyl-substituted 2-acetylpyridine thiosemicarbazones: Cytotoxicity against human tumor cells, structure–activity relationship studies and investigation on the mechanism of action

N(4)-Phenyl 2-acetylpyridine thiosemicarbazone (H2Ac4Ph; N-(phenyl)-2-(1-(pyridin-2-yl)ethylidene)hydrazinecarbothioamide) and its N(4)-ortho-, -meta- and -para-fluorophenyl (H2Ac4oFPh, H2Ac4mFPh, H2Ac4pFPh), N(4)-ortho-, -meta- and -para-chlorophenyl (H2Ac4oClPh, H2Ac4mClPh, H2Ac4pClPh), N(4)-ortho-, -meta- and -para-iodophenyl (H2Ac4oIPh, H2Ac4mIPh, H2Ac4pIPh) and N(4)-ortho-, -meta- and -para-nitrophenyl (H2Ac4oNO(2)Ph, H2Ac4mNO(2)Ph, H2Ac4pNO(2)Ph) derivatives were assayed for their cytotoxicity against human malignant breast (MCF-7) and glioma (T98G and U87) cells. The compounds were highly cytotoxic against the three cell lineages (IC(50): MCF-7, 52-0.16 nM; T98G, 140-1.0 nM; U87, 160-1.4 nM). All tested thiosemicarbazones were more cytotoxic than etoposide and did not present any haemolytic activity at up to 10(-5)M. The compounds were able to induce programmed cell death. H2Ac4pClPh partially inhibited tubulin assembly at high concentrations and induced cellular microtubule disorganization.

Gold(I) complexes with thiosemicarbazones: Cytotoxicity against human tumor cell lines and inhibition of thioredoxin reductase activity

Complexes [Au(H2Ac4DH)Cl]∙MeOH (1) [Au(H(2)2Ac4Me)Cl]Cl (2) [Au(H(2)2Ac4Ph)Cl]Cl∙2H(2)O (3) and [Au(H(2)2Bz4Ph)Cl]Cl (4) were obtained with 2-acetylpyridine thiosemicarbazone (H2Ac4DH), its N(4)-methyl (H2Ac4Me) and N(4)-phenyl (H2Ac4Ph) derivatives, as well as with N(4)-phenyl 2-benzoylpyridine thiosemicarbazone (H2Bz4Ph). The compounds were cytotoxic to Jurkat (immortalized line of T lymphocyte), HL-60 (acute myeloid leukemia), MCF-7 (human breast adenocarcinoma) and HCT-116 (colorectal carcinoma) tumor cell lines. Jurkat and HL-60 cells were more sensitive than MCF-7 and HCT-116 cells. Upon coordinating to the gold(I) metal centers in complexes (2) and (4), the cytotoxic activity of the H2Ac4Me and H2Bz4Ph ligands increased against the HL-60 and Jurkat tumor cell lines. 2 was more active than auranofin against both leukemia cells. Most of the studied compounds were less toxic than auranofin to peripheral blood mononuclear cells (PBMC). All compounds induced DNA fragmentation in HL-60 and Jurkat cells indicating their pro-apoptotic potential. Complex (2) strongly inhibited the activity of thioredoxin reductase (TrxR), which suggests inhibition of TrxR to be part of its mechanism of action.

Spectroscopic studies of metal complexes containing π-delocalized sulfur ligands. The resonance raman spectra of the iron(II) and iron (III) complexes of the antitumor agent 2-formylpyridin thiosemicarbozone

Abstract The resonance Raman spectra of the Fe(II) and Fe(III) complexes of 2-formylpyridine thiosemicarbazone have been measured in acid (pH 3.94.2) and alkaline (pH 7.4) aqueous media. In the spectra of both compounds the bands most strongly enhanced are due to skeletal modes (primarily CN and CS stretches) and ring deformations. On the basis of these results the strong visible absorption of these complexes is attributed to a pπ(s) → σ *(Fe) ligand to metal charge transfer transition. Moreover, the excitation profiles of the Fe(II) complex show a progression of peaks with regular spacing, which are interpreted as arising from successive vibrational levels involving the CS stretching mode. CN vibrations are very sensitive both to metal charge and protonation of the ligand whereas the CS vibrational frequencies are only dependent on metal charge. These results suggest appreciable dππ metalsulfur back bonding in the Fe(II) complex.

Organotin(IV) complexes with 2-acetylpyridine benzoyl hydrazones: antimicrobial activity

Reaction of n-butyltin trichloride, [BunSnCl3], and phenyltin trichloride, [PhSnCl3], with 2-acetylpyridine benzoyl hydrazone (H2AcPh), 2-acetylpyridine para-chloro-benzoyl hydrazone (H2AcpClPh) and 2-acetylpyridine para-nitro-benzoyl hydrazone (H2AcpNO2Ph) gave [BunSn(2AcPh)Cl2] (1), [BunSn(2AcpClPh)Cl2] (2), [BunSn(2AcpNO2Ph)Cl2] (3), [PhSn(2AcPh)Cl2] (4), [PhSn(2AcpClPh)Cl2] (5) and [PhSn(2AcpNO2Ph)Cl2] (6) as products. Among the hydrazones H2AcpClPh proved to be the most active against Staphylococcus aureus and Candida albicans. Upon coordination the antibacterial activity of both tin and the hydrazones significantly increases. Complexes 2 and 5 revealed to be the most active as antimicrobial agents.