José R. Sabino

Docking, Synthesis and Antiproliferative Activity of N-Acylhydrazone Derivatives Designed as Combretastatin A4 Analogues

Cancer is the second most common cause of death in the USA. Among the known classes of anticancer agents, the microtubule-targeted antimitotic drugs are considered to be one of the most important. They are usually classified into microtubule-destabilizing (e.g., Vinca alkaloids) and microtubule-stabilizing (e.g., paclitaxel) agents. Combretastatin A4 (CA-4), which is a natural stilbene isolated from Combretum caffrum, is a microtubule-destabilizing agent that binds to the colchicine domain on β-tubulin and exhibits a lower toxicity profile than paclitaxel or the Vinca alkaloids. In this paper, we describe the docking study, synthesis, antiproliferative activity and selectivity index of the N-acylhydrazone derivatives (5a–r) designed as CA-4 analogues. The essential structural requirements for molecular recognition by the colchicine binding site of β-tubulin were recognized, and several compounds with moderate to high antiproliferative potency (IC50 values ≤18 µM and ≥4 nM) were identified. Among these active compounds, LASSBio-1586 (5b) emerged as a simple antitumor drug candidate, which is capable of inhibiting microtubule polymerization and possesses a broad in vitro and in vivo antiproliferative profile, as well as a better selectivity index than the prototype CA-4, indicating improved selective cytotoxicity toward cancer cells.

Design, synthesis, antinociceptive and anti-inflammatory activities of novel piroxicam analogues.

In this paper we report the design, synthesis, antinociceptive and anti-inflammatory activities of a series of benzothiazine N-acylhydrazones 14a–h, planned by structural modification of piroxicam (1), a non steroidal anti-inflammatory drug. Among the synthesized analogues, compounds 14f (LASSBio-1637) and 14g (LASSBio-1639) were identified as novel antinociceptive and anti-inflammatory prototypes, active by oral administration, acting by a mechanism of action that seems to be different from that of piroxicam, since they were inactive as an inhibitor of cyclooxygenase (COX-1 and COX-2) at concentrations of 10 μM.

Biotransformation of LASSBio-579 and pharmacological evaluation of p-hydroxylated metabolite a N-phenylpiperazine antipsychotic lead compound.

Using a combination of docking and molecular dynamics simulations, we predicted that p-hydroxylation by CYP1A2 would be the main metabolic pathway for the 1-[1-(4-chlorophenyl)-1H-4pyrazolylmethyl] phenylhexahydropiperazine, LASSBio-579 (3). As the result of a screening process with strains of filamentous fungi, Cunninghamella echinulata ATCC 9244 was chosen to scale up the preparation of the p-hydroxylated metabolite (4). About 30 min after i.p. administration of (3) to rats was identified as the p-hydroxylated metabolite, confirming our in silico previsions. Chemical synthesis of the metabolite was performed and allowed its pharmacological evaluation in binding assays revealing its high affinity for D2 and D4 receptors, indicating that this metabolite should participate to the antipsychotic effect of (3) in vivo. Furthermore, we report here that both (3) and its p-hydroxylated metabolite (4) have a much lower affinity than clozapine for two receptors involved in adverse reactions. Voltammetric assays were useful to understand the redox profile of (3).

Structure and theoretical approaches to a chalcone derivative

Chalcones are α,β-unsaturated aromatic ketones which can present a wide range of biological activities. Here, the structure of the chalcone (E)-1-(4-biphenyl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one was determined by single crystal X-ray diffraction technique and compared to those of similar compounds whose crystal structures are available in the Cambridge Structural Database. These comparisons have allowed us to conclude that electron delocalization is abrogated through the biphenyl and carbonyl moieties, while resonance effects are increased through the trimethoxyphenyl group and the olefin carbons. Single-molecule calculations of the asymmetric unit using the DFT method have strengthened these structural relationships, since experimental and theoretical molecular geometries were similar. For instance, the global minimum for the optimized structure occurs when one of the four dihedral angles on the bridge between the two rings of biphenyl is 40.25°, a value close to that of the corresponding torsion determined by single crystal X-ray diffraction analysis [41.7(3)°]. Our theoretical approaches further suggest another stable conformer for different torsions around this bridge, although this conformer was not found in the crystal phase because C–H···π intermolecular interactions contributing to assemble the supramolecular architecture of the studied compound keep only the conformer observed. Other face-to-face π···π stacking interactions and C–H···Ο contacts are also responsible for the crystal assembly.

Synthesis of 3-bromotetronamides via amination of 3,4-dibromofuran-2(5H)-one

This work describes the direct synthesis of 3-bromotetronamides in good yields through the reaction of 3,4-dibromofuran-2(5H)-one, obtained from furfural, with primary and secondary amines. Aromatic amines were more tolerated than aliphatic and heteroaromatic ones. The X-ray structures of five derivatives are described

Guanylation of thiosemicarbazones: a new synthetic route to polysubstituted guanylhydrazones with antimicrobial activity

Guanil-hidrazonas poli-substituidas foram sintetizadas atraves da reacao de guanilacao de tiossemicarbazonas com aminas aromaticas e alifaticas, promovida HgCl 2 . Este metodo representa o primeiro emprego de tiossemicarbazonas como componente eletrofilico em reacoes de sintese de guanidinas mediadas por tiofilo, onde a introducao de cada substituinte dos nitrogenios das guanil-hidrazonas ocorreu de forma regiosseletiva. As atividades antibacteriana e antifungica foram avaliadas e alguns derivados mostraram atividade em valores pequenos de concentracao inibitoria minima e com amplo espectro de atividade. Estudou-se a estrutura cristalina de duas guanil-hidrazonas, determinando-se suas configuracoes e, as unicas interacoes relevantes observadas foram intermoleculares do tipo N–H...N e C–H...N. Thiosemicarbazones were employed for the first time as electrophiles in the guanylation reaction promoted by HgCl 2 , affording polysubstituted guanylhydrazones, with regioselective introduction of each nitrogen substituent. The antibacterial and antifungal activities of guanylhydrazones were evaluated by determination of minimal inhibitory concentrations. Some of them exhibited very low minimal inhibitory concentrations (MIC) and broad-spectrum activities. The configurations of two guanylhydrazones were assigned by X-ray analysis that also revealed intramolecular interactions of the type N–H...N and C–H...N.

Mycoleptones A-C and Polyketides from the Endophyte Mycoleptodiscus indicus

Three new azaphilones with an unusual methylene bridge, named mycoleptones A, B, and C (2, 4, and 5), were isolated from cultures of Mycoleptodiscus indicus, a fungus associated with the South American medicinal plant Borreria verticillata. Additionally, four known polyketides, austdiol (1), eugenitin (3), 6-methoxyeugenin (6), and 9-hydroxyeugenin (7), were also isolated. The structural characterization of compounds was carried out by nuclear magnetic resonance spectroscopy, high-resolution mass spectrometry, electronic circular dichroism spectroscopy, time-dependent density functional theory calculations, and X-ray crystallography. Compounds 1-9 were weakly active when tested in antileishmanial and cytotoxicity assays.

Amaiouine, a Cyclopeptide Alkaloid from the Leaves of Amaioua guianensis

Amaiouine, a cyclopeptide alkaloid, was isolated from the ethanolic extract of the leaves of Amaioua guianensis. The structure was elucidated by NMR spectroscopy and confirmed by X-ray crystallography.

Design of new dopamine D2 receptor ligands: biosynthesis and pharmacological evaluation of the hydroxylated metabolite of LASSBio-581.

LASSBio-581 is a N-phenylpiperazine derivative designed for the treatment of schizophrenia. In this study, four strains of filamentous fungi were screened for their capabilities to biotransform LASSBio-581. Cunninghamella echinulata ATCC 9244 was chosen to scale up the biosynthesis of the p-hydroxylated metabolite of LASSBio-581. The chemical structure of the metabolite was confirmed by NMR, LC-MS and X-ray crystallography. Binding studies performed on brain homogenate indicated that the p-hydroxylated metabolite can be considered more selective for dopamine receptors than LASSBio-581, and, therefore, can be used to design new selective dopamine inhibitors.

Antinociceptive, anti-inflammatory and anxiolytic-like effects of the ethanolic extract, fractions and Hibalactone isolated from Hydrocotyle umbellata L. (Acariçoba) – Araliaceae

Hydrocotyle umbellata Linn. (Araliaceae) is specie used in the treatment of inflammatory diseases. Crude extract (E-HU) was prepared from H. umbellata subterraneous parts and fractionated by liquid-liquid partition, resulting hexane fraction (HF-HU), dichloromethane fraction (DF-HU), ethyl acetate fraction (EAF-HU) and aqueous fraction (AF-HU). The hibalactone (HU-1) was isolated from the DF-HU and its structure was elucidated by 1H NMR and 13C NMR Spectroscopy, mass spectrometry and crystallographic x-ray analysis. The formalin-induced nociception was used to evaluate antinociceptive activity; carrageenan-induced edema and pleurisy tests to evaluate anti-inflammatory activity and light-dark box to evaluate anxiolytic-like activity in mice. The acute oral treatments with E-HU (1000mg/kg), DF-HU (150mg/kg), EAF-HU (400mg/kg) and HU-1 (33mg/kg) decreased the licking time in both phases of the formalin test. In the carrageenan-induced inflammation models, the treatment with the same doses of E-HU, DF-HU, EAF-HU and HU-1 reduced the paw edema formation and leukocytes account into pleural cavity. In silico findings suggest that hibalactone present anti-inflammatory activity by interacting with the enzymes 5-lipoxygenase and cyclooxygenase-2. In the light dark box, the treatments with DF-HU, EAF-HU and HU-1 revealed an anxiolytic like effect. Thus, the E-HU and fractions of H. umbellata showed antinociceptive, anti-inflammatory and anxiolytic like activities, as also hibalactone, a possible phytoconstituent responsible for the biological effects of this specie.