Mycotoxins are low-molecular-weight natural products with great structural diversity produced as secondary metabolites by fungi. One of the principal toxic fungal metabolites is patulin (PAT), produced by over 30 genera of mold including species as Penicillium expansum or Penicillium griseofulvum, and normally related to vegetable-based products and fruit, mainly apple. These mold grow easily in damaged fruit or in derived-product as juices if storage conditions are deficient. Some of the most serious effects of PAT ingestion are agitation, convulsions, edema, ulceration intestinal, inflammation and vomiting. Thus, European Regulation 1881/2006 established a maximum content of 10 ppb in infant fruit juices, 50 ppb for fruit juices in adults and 25 ppb in fruit-derived products. Nowadays, the official analytical method for food adopted by AOAC International is HPLC with UV detection, using clean-up with ethyl acetate and sodium carbonate. However, the diverse drawbacks of this method (poor stability of PAT under alkaline extraction, poor resolution between PAT and co-extracted hydroxymethylfurfural) have originated interest in alternative options, such as LC methods coupled to mass spectrometry. In the last years, purification with molecularly imprinted polymers (MIP) started to be used, and are becoming promising materials for extracting different analytes present in food. Mycotoxins are too toxic or too expensive to be used as template molecules in MIP preparation. Template “bleeding” may be an additional problem, especially when dealing with very low detection levels. In the present work, a rapid and selective method based on magnetic molecularly imprinted stir-bar (MMIB) extraction has been developed for the isolation of PAT. A structural analogue, 2-oxindole, was used as dummy template. The polymer was grafted to the silanized glass surface of the stir bar. 

Benzimidazole and its derivatives have been studied in ion recognition systems that display color changes or fluorescence quenching or enhancement upon binding. Acidity of the NH can be modulated by the presence of heterocycles, such as thiophene, pyrrole, and furan, electronically connected to the imidazole group, as a way to enhance intramolecular electronic delocalization. Furan, pyrrole and thiophene are also known for their interesting photophysical properties, which enable their use as fluorescent sensors and markers, among other applications.

Detecting metallic cations is of great interest as mercury, lead, and cadmium are some examples of cations that are toxic for living organisms, and easy detection in the environment is desirable. Also, many metallic cations are involved in biochemical reactions and their correct balance within cells or living systems is mandatory for health. Metallic cations can be complexed through N, O and S donor atoms in aromatic heterocycles. Hg²⁺ or its methylated derivative can be taken up in the food chain of aquatic organisms doing huge harm to humans and nature. Iron is the most abundant transition metal in cellular systems, more specifically, Fe³⁺ is an essential element in the growth and development of living systems as well as in many biochemical processes at cellular level.

Following our previous work on fluorimetric and colorimetric heterocyclic chemosensors, we now report the interaction studies of a family of benzimidazoles attached to furan, pyrrole and thiophene with biologically important cations, through spectrophotometric and spectrofluorimetric titrations.

The curing reaction of a system consisting of a diglycidyl ether of bisphenol-A (n= 0) and ZnTPyP (Zinc 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphyrin) was studied by Fourier Transform infrared spectroscopy (FTIR). A semi-empirical quantum chemistry program (MOPAC) was used to corroborate the experimental data. The tertiary amine ZnTPyP not only initiates the reaction but also reacts with the resin forming pyridone. This study demonstrates that macrocycles can be used as cross-linking agents for curing epoxy resins and that when metallomacrocycles are used, metal ions can be introduced into the network structure.

Pyridinium salts are very useful synthetic building blocks to obtain substituted pyridines, dihydropyridines or piperidines. Furthermore, pyridinium dyes present applications on multiple fields including biological and optical responses due to their photophysical features, in particular, high fluorescence, charge transfer character and solvatochromic properties. Recently, pyridinium-chitosan derivatives have shown NLO behaviour at molecular level as well as intrinsic fluorescent features.

Different methods are available for the synthesis of pyridinium salts depending on the symmetry around of the cation. One of them involves the use of pyrylium salts as precursor. The synthesis of pyrylium tetrafluoroborate salts can be achieved by direct reaction of 4-substituted benzaldehydes with 4-substituted acetophenones or via the previously obtained chalcone of the less reactive ketone by using Lewis acid catalyst which mediate cyclisation step. This kind of compounds constitutes a promising class of tunable emission wavelength dyes for laser technology applications.

Herein, we report the synthesis and characterization of new pyridinium-chitosan derivatives by reaction of this bipolymer with electronically tunable 2,4,6-tri-arylpyrylium tetrafluoroborates in mild conditions to preserve the original physicochemical properties of the biopolymer. Fluorescence studies have been also performed on polymeric biomaterial in order to demonstrate the redox sensor behaviour.

The synthesis of novel hydrogen-bonded [2]rotaxanes employing an acylaminopyridine-containing thread as template is described. The electronic nature of the starting aroyl chloride employed as macrocycle precursor plays an important role in the formation of the hydrogen-bonding interactions of the supramolecular precursors of the interlocked architectures. Indeed, whereas the preparation of the rotaxane employing isophthaloyl chloride and the pyridine-based template was unfeasible, the introduction of nitro substituent at the position of the same precursor allowed the formation of the target amide-based rotaxane.

Stabilization standards of PVC films are fundamentally depend on essential laws: solvation and "reverberation" Stabilization. The photo-stabilization of poly(vinyl chloride) (PVC) films by epoxidized oleic acid was investigated. Photo-stabilization activities were determined by monitoring the carbonyl, polyene and hydroxyl indices with irradiation time. The changes in viscosity average molecular weight of PVC with irradiation time were also tracked using tetrahydrofuran as a solvent. The quantum yield of the chain scission (Φcs) was evaluated and found with range 4.53´10-8 and 8.12´10-8. Postulated mechanisms were outlined depending on the structure of the additive.

Vinyl phosphonates are well-known constituents of the family of phosphorus containing organic compounds. They are of extensive importance in synthetic organic chemistry both as intermediates and as final products, and have different applications as monomers and co-monomers in polymeric materials. At present, main methods for the synthesis of vinyl phosphonates are based on Pd, Cu or Ni catalysts, but most of them require the use of phosphine ligands and/or severe reaction conditions. In the last years, we have actively been working in the development of new and mild methodologies based on the use of bare or supported copper nanoparticles (CuNPs) for their application in the construction of C-C and C-heteroatom bonds. In a recent publication, we informed the direct synthesis of vinyl phosphonates catalyzed by CuNPs supported on ZnO starting from aliphatic alkynes and commercial diethyl phosphite. The reactions were carried out in acetonitrile as solvent, in the absence of any additive or ligand, and under mild reaction conditions. Notably, the use of ZnO as support and MeCN as solvent was mandatory for the reaction to take place. Besides, we conducted a series of experiments in order to get some information about the mechanism involved. The addition of TEMPO, a radical scavenger, did not affect the formation of the vinyl phosphonate product; therefore, it should take place through a non-radical process under the reaction conditions. Additionally, the reaction carried out by using 1-deuterio-oct-1-yne as starting alkyne, led to the corresponding deuterated-vinyl phosphonate product, thus suggesting that copper acetylide species would not participate as intermediates, and thus the reaction is more likely to occur via a copper-catalyzed anti-Markovnikov hydrophosphorylation process, leading to the corresponding vinyl phosphonates through the addition of the (EtO)₂(HO)P: nucleophile to the carbon-carbon triple bond. We assume that ZnO (Lewis basic sites) could be playing a non-innocent role in the catalytic system, probably through the P-H bond activation. With the aim to explain and understand these experimental results, we performed a computational analysis using DFT methods (GAUSSIAN09). Based on the experimental data, the previous reports by other authors and the results showed by our DFT studies, we have proposed a possible reaction mechanism that implies an active role of ZnO and MeCN in different steps of the reaction. As preliminary results, DFT studies showed a strong coordination between both metals, Cu and Zn, and P=O oxygen atom, consequently, the participation of cyclic structures as intermediates is favoured in these CuNPs/ZnO-catalyzed hydrophosphorylation of aliphatic alkynes.

Flavonoids are bioactive compounds that can display antioxidant activity. Their must important source is the vegetal kingdom. Their composition in different foods is compiled into several databases organized by USDA. This information enabled the creation of a data record that was used in the work to predict the total antioxidant capacity of food by the oxygen radical absorbance capacity (ORAC) method, using algorithms of artificial intelligence. K-Nearest Neighbors (KNN) was used. The attributes were: a) amount of flavonoid, b) class of flavonoid, c) Trolox equivalent antioxidant capacity (TEAC) value, d) probability of clastogenicity and clastogenicity classification by Quantitative Structure-Activity Relationship (QSAR) method and e) total polyphenol (TP) value. The selected variable to predict was the ORAC value. For the prediction, a cross-validation method was used. For the KNN algorithm, the optimal K value was 3, making clear the importance of the similarity between objects for the success of the results. It was concluded the successful use of the KNN algorithm to predict the antioxidant capacity in the studied food groups.

ABSTRACT

Enterococci are Gram-positive bacteria responsible for causing multiple nosocomial infections in humans. Chemoinformatics could be a great ally of medicinal chemistry in the search for efficacious anti-enterococci drugs. Current methods cannot model the anti-enterococci activity and ADMET (absorption, distribution, metabolism, elimination, toxicity) properties at the same time. We create the first multitasking model for quantitative-structure biological effect relationships (mtk-QSBER), focused on the simultaneous prediction of anti-enterococci activities and ADMET profiles of compounds.  The mtk-QSBER model was constructed by using a large and heterogeneous dataset of chemicals, and exhibited accuracy higher than 95% in both training and prediction sets. We provided the physicochemical interpretations of the molecular descriptors (probabilistic quadratic indices) that entered in the model. In order to demonstrate the practical utility of our model, we predicted multiple biological profiles of the investigational antibacterial drug oritavancin, and the results of the virtual predictions strongly converged with the experimental evidences. To date, this is the first attempt to use a unified in silico model to guide drug discovery in antimicrobial research by predicting the antibacterial potency against enterococci, as well as the safety in laboratory animals and humans.

Transforming growth factor β receptor-associated kinase 1 (TAK1) or mitogen activated-protein kinase kinase kinase 7 (MAP3K7) is a serine/threonine kinase which forms a key part of canonical immune and inflammatory signaling pathways. A 5-point pharmacophore model was developed and the generated pharmacophore model was used to derive a predictive atom-based 3D quantitative structure–activity relationship analysis (3D-QSAR) model for the studied dataset. The obtained 3D-QSAR model has an excellent correlation coefficient value (r² = 0.97) along with good statistical significance as shown by high Fisher ratio (F = 266.8). The QSAR model suggests that electron-withdrawing character, hydrogen bond-donating groups, hydrophobic and negative ionic groups positively contribute to the TAK1 inhibition.