Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

In the present study, the interaction of transition cations in their divalent states Cu2+, Co2+, Zn2+ and Mn2+, which act as bridges when interacting with carboxylic groups of alginate and graphene oxide, was studied. The chemical nature of the interactions under study was determined using the natural bond orbitals (NBO) method, topological analysis of the electronic location function (ELF), and the quantum theory of atoms in molecules (QTAIM). The results showed that the interactions between the metals under study with the carboxylic groups of alginate and graphene oxide are of the coordinated type with a high electrostatic component.

In the search of new organometallic precursors, this contribution describes a convenient synthesis to obtained new ferrocene-based sulfonyl diamine derivatives. The [(η5-C5H4SO2NH-CH2-CH2-NH2)Fe(η5-C5H5)] (1) and [(η5-C5H4SO2NH-C6H4-NH2)Fe(η5-C5H5)] (2) compounds were prepared by the reaction between (η5-C5H4SO2Cl)Fe(η5-C5H5) and the respective diamine precursor: ethylenediamine (1) or p-phenylenediamine (2) in good yields (86% for 1; 70% for 2). Both compounds were characterized by conventional spectroscopic techniques (infrared spectroscopy, nuclear magnetic resonance spectroscopy, mass spectrometry and elemental analysis) and cyclic voltammetry. In addition, the molecular structure of 1 was determined by single-crystal X-ray diffraction.

In recent decades the increase in the use of plastics has been exponential around the world, reaching a presence in places such as rivers, oceans and lakes, as well as in terrestrial environments such as agricultural soils. Associated with the great use of plastics in all areas of work, plastic particles smaller than 5 mm, called microplastics, have been found in all environmental matrices: aquatic environment, dispersed throughout the water column, terrestrial environment, infiltrating the soil sedimenting, and in the air, being transported by the wind. In each of these matrices, microplastic serves as transport for highly polluting compounds such as heavy metals, polycyclic aromatic hydrocarbons and organochlorine pesticides. In addition to environmental matrices, microplastics have been found in animals and humans in alarming numbers. In this way, this review addresses issues related to the formation and distribution of microplastics throughout the ecosystem and different organisms.

Described are the physicochemical and microbiological parameters of glacial water sourced of Glacier Mapa, Andes Mountains, Chile. The study is performed of isotopic composition in collaboration with Oleg Mosin. Glacier Mapa is located 55 km from the town of Los Andes in direction of Argentina. The water of the given source Glacier Mapa, Chile is characterized by microbiological indicators. Research is conducted for Coliforms, Escherichia coli, Enterococci and Clostridium perfringens. The pathogenic micro-organisms in the samples of the glacial water from the source mentioned above are determined by the methods according to Ordinance No. 9/2001, Official State Gazette, issue 30, and decree No. 178/23.07.2004 of Council of Ministers, Bulgaria about the quality of water, intended for drinking and household purposes. The parameters of the physicochemical composition include 18 indicators and are determined according to Ordinance No. 9/2001 (Protocol No. 12735/17.03.2016 of licensed laboratory Eurotest control, Sofia, Bulgaria). The physicochemical and microbiological parameters of glacier water Mapa, Chile, correspond to all controlling parameters and are in accordance with Ordinance No. 9/2001 (Official State Gazette, issue 30 about the quality of water, intended for drinking and household purposes). The natural waters consist 99.7 mol. % of H216O, which are formed by 1H and 16O atoms (Jouzel, 2003; Mosin, Ignatov, 2011). The remaining 0.3 mol.% is distributed in isotope varieties (isotopomers) of water molecules, whose deuterium atoms form 6 configurations – HD16O, HD17O, HD18O, D216O, D217O, D218O, as 3 configurations are formed by isotopes of oxygen – Н216O, Н217O, Н218O. Studies of International standard SMOW of isotopic shift for D were performed for D/H for water from Glacier Mapa, Chile.   The results obtained of glacier water Mapa, Chile show a lower content of hydrogen and oxygen isotopes. It is not confirmed presence of pathogenic micro-organisms. The physicochemical indicators are typical for waters during the ice melting in glacier water (Ca2+ 6.0; Mg2+ 1.0; Na+ 5.0; K+ 0.38; HCО3- 73.8 /mg. L-1).                       Glacier water Mapa is soft with total mineralization – 100.1 mg.L-1. The water of Glacier Mapa is beneficial for the health according to the indicated physicochemical, microbiological and isotopic parameters.  

Currently, the results of researches have exhibited that Omicron sub-lineages BA.4 and BA.5, evaluated to BA.1 and BA.2, deserted neutralization from sera of triple vaccinated particulars to a bigger extension. Therefore, a novel wave of Omicron virus has appeared driven by BA.4 & BA.5 subvariants. Nanocarriers contain carbon atoms with functional nanostructures, which not only help the improved mechanical properties but also indicate the bioactivities for regulating cell status. In this research, asafoetida as a medicinal plant can be applied in treatment for Omicron subvariants BA.4 and BA.5 through adsorbing of its effective compound of ferulic acid on the surface of (6,6) armchair single-walled carbon nanotube as the drug delivery model due to direct electron transfer principle which has been studied by density functional theory (DFT) methods. On the other hand, it has been accomplished the B3LYP/6-311+G (2d,p) level of theory to evaluate the aptitude of SWCNT for adsorbing effective compound in  asafoetida medicinal plant through nuclear magnetic resonance and thermodynamic parameters. In fact, the achieved results have represented that the feasibility of using (6,6) armchair SWCNT and ferulic acid becomes the norm in drug delivery system which has been attained by quantum calculations due to physico-chemical properties of NMR, IR and UV-VIS spectroscopy. Besides, the energy gap analysis of HOMO-LUMO has illustrated the charge distribution in the frontier molecular orbitals of ferulic acid in asafoetida drug through adsorption on the surface of (6,6) armchair carbon nanotube (CNT).

Allelopathy is one of the alternatives used for integrated weed management (IWM), in order to minimize the use of synthetic herbicides. Allelopathy is defined as the effect produced by a chemical released by a donor plant on the development of another competitive recipient plant. Research on allelopathic interactions has been focused on agricultural crops, and allelopathic activity of indole alkaloids has been reported in cereals such as barley (Hordeum vulgare L.), whose principal natural secondary metabolite is Gramine. The degradation products of this metabolite in agricultural soils have not been investigated, however indole and derivatives substituted in aromatic ring and heterocyclic can be produced, so the role of soil in the allelopathic behavior of these compounds is not yet clear. In this work, phytotoxicity and dynamics of Gramine, indole and model series of substituted indoles in position 2 and 3 of the aromatic ring and position 5 of the aromatic ring were investigated in order to understanding the role of this metabolite in the allelopathy property of cereal barley. The phytotoxic activity against competitive cereals and weeds was determined in soil, from which the percent inhibition (% I) of seed germination and seedling growth was measured. In adsorptions study, according to the values obtained from the adsorption coefficient (Kd), it was obtained that all the series of indole alkaloids shows a moderate adsorption in Alhue soil, with the exception of indole 3-acetic acid. In the study of desorption, this compound showed a desorption percentage of 81%, according to the Kd values obtained. The persistence studies indicated a half-life (t1/2) with a range of values between 7 h and 18 days for the series of indole alkaloids studied, where the highest value of t1/2 was for indole 2-carboxylic acid and the minor one for indole 5-carbaldehyde. The dynamics of the compounds in Alhue soil affect phytotoxic activity, as well as bioavailability, so that soil plays an essential role in the phytotoxic effect of the compounds. Indole and Indole 2-carboxylic acid had the greatest phytotoxic effect, this behavior can be attributed to its greater persistence and low adsorption, that is, they are more bioavailable in Alhue soil and so the role as an allelochemical would be favorable.

Ibuprofen is one of the most widely used nonsteroidal anti-inflammatory drugs due to its analgesic, anti-inflammatory and antipyretic properties, as well as its low cost and easy accessibility. A fraction of the compound and its metabolites are excreted in the urine, being eliminated in the wastewater reaching river waters in the range of ng L-1 to µg L-1. In this context, highly sensitive and selective analytical methods are required to quantify them, including these methods a pre-concentration step. In this work, the use of a microextraction technology based on rotating-disk sorptive extraction, involving a sorptive phase of laminar cork, was implemented for the extraction of ibuprofen and 1-hydroxyibuprofen from aqueous samples and their subsequent determination by gas chromatography coupled to mass spectrometry. The optimal conditions for determination of the analytes were: 20 mL of sample volume, pH 2, 20 % w/v NaCl (to increase the ionic strength), 90 min of extraction time and 2000 rpm of rotation velocity of the disk. Recoveries of 118 and 39 % and relative standard deviations of 6 and 13 % for ibuprofen and 1-hydroxyibuprofen were obtained, respectively. The presence of both compounds in river waters (Mapocho River, Santiago de Chile) at a concentration of 2.56 to 4.08 µg L-1 were found. The use of laminar cork as a natural sorbent phase immobilized in the rotating-disk allowed to extract the analytes from water samples through its lipophilic-hydrophilic balance that favors the interaction with the compounds under study.  

The solid state thione-thiol equilibrium in 4,6-di­phenyl-3,4-di­hydro­pyrimidine-2(1H)-thione (C16H14N2S) is analyzed through three different techniques, viz: Single Cristal X-Ray Diffraction (SCXRD), Nuclear Magnetic Resonance (NMR) and Fourier Transformed Infra-Red spectroscopy (FTIR), each one providing complementary information to the solution of the problem. The existence of thione-thiol equilibrium is firmly established, both in solution (by HNMR techniques) as in the solid state (by FTIR methods), and even if no traces of the thiol form could be found via SCXRD, some hints about the way in which the coexistence of both forms could be structurally achieved are provided by the structural analysis. In order to confirm the existence of this equilibrium, theoretical calculations were carried out at the B3LYP/6-311G(d,p) level theory, and a double proton transfer reaction is proposed.  

The use of the Potassium Nitrate as an oxidizer in solid rocket propellants has been common in recent years for experimental research in solid rocket propulsion systems. This chemical is used as a compound of black powder and explosives, but in the last 30 years, it has been studied for applications in semiprofessional rocket propellant, implemented by Universities in research and academic projects. The Potassium Nitrate/Dextrose propellant is also known as Candy propellant and presents some advantages compared with other solid propellants. They are low production costs and ease of acquisition for the chemical components. These advantages are attractive for low-cost projects, compared to the low performance; this does not discourage its use. The Candy propellant presented a lack of experimental data to characterize, for example, its thermal properties. For this reason, were used the Differential Scanning Calorimetry and the Semi-Micro Calorimetry tests, to obtain the heat of combustion, power, and temperatures of melting and ignition. The grains of Candy propellant were manufactured at the University of Conception by the Propulsion Interest Team. This is the first time which is reported the calorimetric data of the Candy propellant (Potassium Nitrate/Dextrose). The results in this work presented a heat combustion in the range 523 - 567 Cal·g−1, decomposition temperature in the range 356 - 361 °C and a heat released in the range 1080 - 1809 J·g−1 of the mixture KNO3/Dextrose, which contribute to the professional characterization of the propellant.

Phytochemical analysis of the basidiomycete Cortinarius magellanicus (family Cortinariaceae) resulted in the isolation of eight secondary metabolites, where a brominated secondary metabolite was isolated for first time from a natural source. The structure elucidation of this compound was made using one- and two-dimensional NMR experiments, FT-IR, GC-MS, HRESIMS and chemical derivation. The disk diffusion assay of the brominated compound 4 and 8 revealed a low inhibition on Gram-positive and Gram-negative bacteria, respectively. No antifungal activities were detected for these compounds.