Bernardo L. Rodrigues

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.

1,2,3-triazole-, arylamino- and thio-substituted 1,4-naphthoquinones: potent antitumor activity, electrochemical aspects, and bioisosteric replacement of C-ring-modified lapachones.

1,2,3-Triazole-, arylamino- and thio-substituted naphthoquinones (24, 8, and 2 representatives, respectively) were synthesized in moderate yields and evaluated against several human cancer cell lines (blood, ovarian, breast, central nervous system, colon, and prostate cancers and melanoma), showing, for some of them, IC50 values below 2 μM. The cytotoxic potential of the tested naphthoquinones was also assayed on non-tumor cells such as human peripheral blood mononucluear cells (PBMC) and two murine fibroblast lines (L929 and V79 cells). α-Lapachone- and nor-α-lapachone-based 1,2,3-triazoles and arylamino-substituted naphthoquinones showed potent cytotoxicity against different cancer cell lines. The compounds may represent promising new lead derivatives for anticancer drug development. The electrochemical properties of selected compounds were evaluated in an attempt to correlate them with antitumor activity.

Metal complexes with 2-acetylpyridine-N(4)-orthochlorophenylthiosemicarbazone: Cytotoxicity and effect on the enzymatic activity of thioredoxin reductase and glutathione reductase

Metal complexes with 2-acetylpyridine-N(4)-orthochlorophenylthiosemicarbazone (H2Ac4oClPh) were assayed for their cytotoxicity against MCF-7 breast adenocarcinoma and HT-29 colon carcinoma cells. The thiosemicarbazone and most of the complexes were highly cytotoxic. H2Ac4oClPh and its gallium(III) and tin(IV) complexes did not show any inhibitory activity against thioredoxin reductase (TrxR) and glutathione reductase (GR). The palladium(II), platinum(II) and bismuth(III) complexes inhibited TrxR at micromolar concentrations but not GR. The antimony(III) and gold(III) complexes strongly inhibited TrxR at submicromolar doses with GR inhibition at higher concentrations. The selectivity of these complexes for TrxR suggests metal binding to a selenol residue in the active site of the enzyme. TrxR inhibition is likely a contributing factor to the mode of action of the gold and antimony derivatives.

Experimental electron density of urea–phosphoric acid (1/1) at 100 K

The deformation electron density of the urea-phosphoric acid adduct has been studied from 100 K X-ray and neutron diffraction experiments. Data were interpreted according to the Hirshfeld model. The long hydrogen bonds show characteristics of electrostatic interaction. Deformation density maps on the short hydrogen bond shows hydrogen more strongly bonded to urea than to phosphoric acid, and peak maxima at almost midway between the two O-H bonds.

Novel Triphenylantimony(V) and Triphenylbismuth(V) Complexes with Benzoic Acid Derivatives: Structural Characterization, in Vitro Antileishmanial and Antibacterial Activities and Cytotoxicity against Macrophages

Two novel organoantimony(V) and two organobismuth(V) complexes of the type ML2 were synthesized, with L = acetylsalicylic acid (HL1) or 3-acetoxybenzoic acid (HL2) and M = triphenylantimony(V) (M1) or triphenylbismuth(V) (M2). Complexes, [M1(L1)2] (1), [M1(L2)2]∙CHCl3 (2), [M2(L1)2], (3) and [M2(L2)2] (4), were characterized by elemental analysis, IR and NMR. Crystal structures of triphenylantimony(V) dicarboxylate complexes 1 and 2 were determined by single crystal X-ray diffraction. Structural analyses revealed that 1 and 2 adopt five-coordinated extremely distorted trigonal bipyramidal geometries, binding with three phenyl groups in the equatorial position and two deprotonated organic ligands (L) in the axial sites. The metal complexes, their metal salts and ligands were evaluated in vitro for their activities against Leishmania infantum and amazonensis promastigotes and Staphylococcus aureus and Pseudomonas aeruginosa bacteria. Both the metal complexes showed antileishmanial and antibacterial activities but the bismuth complexes were the most active. Intriguingly, complexation of organobismuth(V) salt reduced its activity against Leishmania, but increased it against bacteria. In vitro cytotoxic test of these complexes against murine macrophages showed that antimony(V) complexes were the least toxic. Considering the selectivity indexes, organoantimony(V) complexes emerge as the most promising antileishmanial agents and organobismuth(V) complex 3 as the best antibacterial agent.

Synthesis and anti-Trypanosoma cruzi activity of naphthoquinone-containing triazoles: electrochemical studies on the effects of the quinoidal moiety.

In our continued search for novel trypanocidal compounds, twenty-six derivatives of para- and ortho-naphthoquinones coupled to 1,2,3-triazoles were synthesized. These compounds were evaluated against the infective bloodstream form of Trypanosoma cruzi, the etiological agent of Chagas disease. Compounds 17-24, 28-30 and 36-38 are described herein for the first time. Three of these novel compounds (28-30) were found to be more potent than the standard drug benznidazole, with IC50/24h values between 6.8 and 80.8μM. Analysis of the toxicity to heart muscle cells led to LC50/24h of <125, 63.1 and 281.6μM for 28, 29 and 30, respectively. Displaying a selectivity index of 34.3, compound 30 will be further evaluated in vivo. The electrochemical properties of selected compounds were evaluated in an attempt to find correlations with trypanocidal activity, and it was observed that more electrophilic quinones were generally more potent.

On the search for potential antimycobacterial drugs: synthesis of naphthoquinoidal, phenazinic and 1,2,3-triazolic compounds and evaluation against mycobacterium tuberculosis

Fifteen naphthoquinones, sixteen phenazines and fifteen aryl triazoles were synthesized and evaluated against Mycobacterium tuberculosis. Twenty five substances are reported here for the first time and, among all of the compounds evaluated, six presented MIC (minimal inhibitory concentration) values < 6.25 µg mL-1. These substances are promising antimycobacterial prototypes.

Tricarbonylrhenium(I) complexes with 2-acetylpyridine-derived hydrazones are cytotoxic to NCI-H460 human large cell lung cancer

Complexes [ReCl(CO)3(H2AcPh)] (1), [ReCl(CO)3(H2AcpClPh)]·0.5C7H8 (2) and [ReCl(CO)3(H2AcpNO2Ph)]·0.5C7H8 (3) were obtained with 2-acetylpyridine-phenylhydrazone (H2AcPh) and its para-chlorophenylhydrazone (H2AcpClPh) and para-nitrophenylhydrazone (H2AcpNO2Ph) analogues. Coordination to tricarbonylrhenium(I) resulted in a higher antiproliferative activity against NCI-H460 human large cell lung cancer. Complexes (2) and (3) induced apoptosis on NCI-H460 cells. Complex (2) induced mitochondrial damage while treatment with 3 showed a later response, suggesting that probably the same effect would be observed at higher concentrations or longer treatments. Both complexes (2) and (3) showed a high antioxidant activity, 2 being more potent in reducing intracellular reactive oxygen species (ROS) production.

Synthesis and Characterization of Cobalt(III), Nickel(II) and Copper(II) Mononuclear Complexes with the Ligand 1,3-bis[(2-aminoethyl)amino]-2-propanol and Their Catalase-Like Activity.

In this work, we present the synthesis and characterization of two new mononuclear complexes with the ligand 1,3-bis[(2-aminoethyl)amino]-2-propanol (HL), [Co(L)(H2O)](ClO4)2 (1), [Ni(HL)](ClO4)2 (2), as well as the known complex [Cu(HL)](ClO4)2 (3) for comparison. Their abilities to catalyze the dismutation of H2O2 and the oxidation of cyclohexane were investigated. The complexes were characterized by X-ray diffraction, elemental analysis, electronic and infrared spectroscopy, cyclic voltammetry, electrospray ionization mass spectrometry (ESI-MS) and conductivity measurements. The X-ray structures showed that the nickel (2) and copper (3) complexes are tetracoordinated, with the metal ion bound to the nitrogen atoms of the ligand. On the other hand, the cobalt complex (1) is hexacoordinated, possessing additional bonds to the alkoxo group of the ligand and to a water molecule. Neither of the complexes was able to catalyze the oxidation of cyclohexane, but all of them exhibited catalase-like activity, following Michaelis-Menten kinetics, which suggest resemblance with the catalase natural enzymes. The catalytic activity followed the order: [Ni(HL)](ClO4)2 (2) > [Cu(HL)](ClO4)2 (3) > [Co(L)(H2O)](ClO4)2 (1). As far as we know, this is the first description of a nickel complex presenting a significant catalase-like activity.

6α,7β‐Dihydroxyvouacapan‐17β‐oic Acid

The title compound, 1,5,5a,6,7,7a,8,9,10,11,11a,11b-dodecahydro-6,7-dihydroxy-8,8,11a- trimethylphenanthro[3,2-b]furan-5-carboxylic acid, C20H28O5, presents both anti-inflammatory and analgesic activities. Two of the six-membered rings adopt chair conformations, whereas the ring fused to furan is in a half-chair conformation. Crystal packing is established by three intermolecular hydrogen bonds.