Please login first

List of accepted submissions

Show results per page
Find papers
  • Open access
  • 108 Reads
DNA-binding properties of cytotoxic naphtindolizinedione-carboxamides acting as type II Topoisomerase inhibitors. A combined in silico and experimental study.

Some clinically used anticancer drugs are DNA intercalators acting as topoisomerase (Topo) IIα poisons in tumor cells highly expressing the enzyme. Synthetic naphtindolizinedione-carboxamides, previously designed as potential antitumor agents and showing relevant cytotoxic activities in vitro, have been now evaluated for their DNA-binding and inhibition of human Topo IIα, in comparison with the drug mitoxantrone. Docking calculation of each synthetic molecule as ligand with the CGCGAATTCGCG oligonucleotide model showed a stable intercalation in the DNA cut inside the enzyme. Moreover, molecular dynamics simulation indicated the stability of each DNA complex by evaluating the H-bonds involved as a function of time. These results are correlated to spectroscopic (binding constants and melting temperature by UV/Vis analysis, circular dichroism) and biological data (cytotoxicity and inhibition of human Topo IIα decatenation assay).

  • Open access
  • 94 Reads
A simple and sustainable synthetic lab-protocol for obtaining racemic dominicalure- aggregation pheromone of the grain beetle Rhyzopertha dominica F. (Coleoptera, Bostrichidae)

The pheromones constitute a decisive component in the push-pull strategies for the development of ecologically sustainable agricultural systems, the conservation of stored foods in the human communities and the preventive anti-vectorial control. Due to their specific atractantt action and minimum ecological impact their rational application that minimize the volume and utilization of plaguicides, these substances are applied intensively in plants protection systems and stored products. In Cuba and Ecuador several studies are developing, under ecosustainable conditions, on synthetic feasibility of pheromones and their applicability in the population control of insects, mainly the specie Rhyzopertha dominica which causes severe damages in stored grains and derivatives. Previously reported information details the use of expensive reagents and inert conditions (Ar atmosphere, temperaturas of -20 and –25 0C, tedious workup) for carrying out the synthesis of the aggregation pheromone of this specie. Using propionic and isobutiric aldehydes as starting substrates were synthesized, by means of aldolic condensation, selective oxidation with Ag2O-methanol of monoenic aldehydes, treatment with SOCl2 and esterificatión with 2-pentanol, the respective components of the racemic aggregation pheromone of this species were synthesized. The NMR 1H-13C structural analysis is detailed for target esters and intermediates, and an attempt of oxidation with TEMPO derivatives is also shown.

  • Open access
  • 105 Reads
Magnetized dextrin: eco-friendly effective nanocatalyst for the synthesis of dihydropyrano[2,3-c]pyrazole derivatives

Dextrin is a water soluble polysaccharide obtained by hydrolysis of starch or glycogen. This low molecular weight biopolymer with valuable properties such as biodegradability, natural origins, good availability and high reactivity can be an appropriate substance to fabricate the environmentally friendly catalysts. The magnetized dextrin was prepared via facile co- precipitation procedure of iron salts in the presences of dextrin under alkaline condition. Then, it was characterized by different conventional analyses. Eventually, the catalytic application of obtained nanocatalyst was evaluated for the synthesis dihydropyrano[2,3-c]pyrazole derivatives through multicomponent reaction of hydrazine hydrate, ethyl acetoacetate, aromatic aldehydes and malononitrile. Utilizing biocompatible nanocatalyst, simple procedure, short reaction times, and catalyst reusability after four consecutive runs with negligible decrease in catalytic efficiency are some merits of presented method.

  • Open access
  • 43 Reads
Synthesis and structure of novel potentially bioactive amphiphilic -O-(N)-glycosides

Carbohydrate-based surfactants are molecules with a sugar hydrophilic moiety and a hydrophobic tail, usually a hydrocarbon chain such as a fatty acid or alcohol. These glycosides have been synthesized and their structures were analyzed in terms of supramolecular arrangements as we see in recent literature. Also, they were proposed as potential therapeutic active molecules. The capability to interact with the lipid bilayer of biological membranes bring them a bioactive profile. In this presentation, we show the design and synthesis of carbohydrate derivatives with amphiphilic properties including a bioactive moiety, a Schiff base. Oxime ether function is an important structural motif in many famous drug scaffolds. Many anti-viral agents have the -C=N-O- function in their structures, for example, the kinase inhibitor "enviroxime" and the recently reported "EIDD-2801" glycoside that has shown broad anti-influenza virus activity. We present here the synthesis and structural analysis of novel -O-(N)-glycosides. The reaction of NHS with penta-O-acetyl-D-glucose or galactose in the presence of BF3.OEt2 gives the b anomer glycoside in a straightforward manner. Further hydrazinolysis and condensation with decanal give the desired products. Their complete structures, including the anomeric and E/Z double bond configurations, were determined by spectroscopic analysis.

  • Open access
  • 78 Reads
ZnFe2O4@dimethylglyoxime: preparation and catalyst application in the synthesis of 2-amino-tetrahydro-4H-chromene-3-carbonitrile derivatives

Hybrid materials constructed from two or more constituents provide new features and distinctive application which is not found in the single-part material. Spinel ferrites with general formula of AB2O4, where A and B represent a divalent metal ion (such as Zn(II), Ni(II), Cu(II),) and Fe(III) ions, appeared as efficient catalysts for the synthesis of organic compound. These magnetic nanoparticles have both the Lewis acid and the Lewis base sites in their structure. In present study, the ZnFe2O4 ferrite was prepared and modified with dimethylglyoxime to obtain magnetic ZnFe2O4@dimethylglyoxime hybrid catalyst. Dimethylglyoxime, N,N′-dihydroxy-2,3-utanediimine, is a dibasic acid substance which has been used as a chelating agent for divalent metal ions due to containing two nitrogen atoms and hydroxyl groups. Surface modification zinc ferrite with this dibasic acid substance produced bifunctional hybrid catalyst with increased active sites. In next step, prepared catalyst was applied in the synthesis of 2-amino-tetrahydro-4H-chromene-3-carbonitrile derivatives by condensation of dimedone, aromatic aldehydes and malononitrile in ethanol at room temperature. The present procedure offers some advantages such as simple procedure, mild reaction condition, short reaction times and retrievablity catalyst.

  • Open access
  • 109 Reads
Chemical fingerprinting and antimicrobial evaluation of the methanolic extract of the leaves of the endemic Cuban plant Coccoloba cowellii

The genus Coccoloba (Polygonaceae) comprises approximately 150 species of flowering plants. It is native to the tropical and subtropical regions of America, in South America, the Caribbean and Central America. A wide variety of biological activities has been studied for Coccoloba species due to great diversity of metabolites (mainly flavonoids, tannins, terpenoids and volatile oils) and popular uses reported for different ailments like fever, diarrhea, menstrual disturbance, uterine hemorrhages, hemorrhoids and gonorrhea. The methanolic extract of the leaves of C. cowellii, endemic of the Camagüey province of Cuba and critically endangered, was subjected to structural analysis. The HPLC-DAD-QTOF-ESI-MS obtained data was analysed employing the MS-DIAL software. A dereplication of the ESI-MS data was realized using the Feature-based Molecular Networking (FBMN) analysis method in the Global Natural Products Social Molecular Networking (GNPS) infrastructure, leading to 12 compound hits against the GNPS database. A total of 13 compounds were tentatively identified by means of MS data, together with the interpretation of the observed MS/MS spectra in comparison with those found in the literature. The major compounds were myricetin and quercetin glucuronides and glycosides and epichatechin-3-O-gallate. The total extract presented an antifungal effect against Candida albicans ATCC B59630 (azole-resistant) (IC50=2.13µg/ml) and was not cytotoxic (IC50>64.00µg/ml) in the resazurin MRC-5 SV2 cell viability assay employed. This is the first report related to chemical composition of C. cowellii plant. The research is now focused on determining the secondary metabolites responsible for the antifungal activity of the total extract.

  • Open access
  • 128 Reads
Structural characterization of the decomposition product of hexamethylenetetramine (HMTA). A combined theoretical and spectroscopic study

Hexamethylenetetramine (HMTA) is a widely known nitrogen heterocycle characterized by a cage-like structure reminiscing the adamantane motif. This versatile compound has an ample array of scientific and technological applications. However, the reactivity of HMTA and the nature of its intermediates at different conditions remains unknown to date. To gain an understanding of its reactivity, we aim to elucidate the intermediates from this amine at the most common employed conditions (high temperature and acidic media). To be able to distinguish among all the possible compounds, we employed an array of analytical and computational techniques in a synergistic way. We combined the use of NMR experiments, chemometric tools, and DFT studies to unveil structural and mechanistic details about the stability and reactivity of the intermediates of HMTA. Applying these techniques, we found that the first stage entails a nitrogen atom-protonation, which is followed by a ring opening to afford an external imine. Then, at high temperature (90°C), a [1,5-H] sigmatropic rearrangement is observed, with the formation of the internal imine. This rearrangement involving two nitrogen atoms is not uncommon and can be carried out thermally or under Lewis acids assistance. We have found that theoretical studies give full support to the mechanism proposed for the formation of the internal imine. These findings add to the current knowledge of the stability of HMTA and may help to explain some of the challenges this substrate has in industrial applications.