Improving the behavior of thermoplastic starch with the addition of gum Arabic: Antibacterial, mechanical properties and biodegradability

The incorporation of different amounts of Gum Arabic (GA) in thermoplastic starch (TPS) obtained by extrusion and subsequent thermocompression has been studied. The sheets have been characterized by means of XRD, FTIR, TGA, moisture content, SEM, mechanical properties, antimicrobial activity and biodegradability via composting. The FTIR analysis of the sheets shows the presence of ester groups, while the TGA shows the presence of new processes and a residue much higher than expected is obtained. No changes in crystallinity are observed by XRD. The inclusion of GA confers antimicrobial properties to thermoplastic starch against the Gram + and Gram – bacteria studied even at the smaller concentrations. For a low GA content (0.5 and 1g GA/100 g TPS) a homogeneous material is observed by SEM, as well as an important increase in tensile strength, modulus and deformation at break, which are very interesting properties facing the applicability of this material in single use plastics which are in contact with food or other consumable goods. At higher contents of GA, hollows and cracks appear in the material, compromising the mechanical properties. In all cases, the inclusion of GA delays the biodegradation process in soil, which can be related to its antibacterial capacity and especially in case of GA concentrations of 2 and 5g /100 g of TPS with lower humidity of these TPS sheets.The authors would like to express their gratitude to the “Convenio-Programa de Doctorado en Ingeniería Química de la Universidad Central del Ecuador (Quito-Ecuador)” and the University of Alicante (Alicante-Spain) for their support

Microbiological activity in biodegradable biopolymers from potato starch and organic substance

El diseño de materiales y envases biodegradables activos es uno de los retos de la sociedad cuyo fin es tratar de resolver los problemas ambientales que se han generado por los residuos plásticos desarrollando envases biodegradables que permitan mejorar la conservación de los alimentos y alargar su vida útil. Se analizó la preparación de una mezcla ideal utilizando almidón de papa termoplástico (AP), extracto de árbol de té (AT) y goma arábiga (GA), obteniendo luego de un proceso de extrusión y prensado las planchas de biopolímero termoplástico, que fueron analizadas para determinar sus propiedades antimicrobianas. Se elaboraron 19 muestras de planchas de biopolímeros con distintas proporciones AP, AT y GA. Los resultados obtenidos de los biopolímeros a base de AP/GA (60/2) y (70/5) mostraron mayores actividades antimicrobianas contra bacterias Gram positivas y negativas, respectivamente, seguidas de las formulaciones con AP/EAT (60/1) y (70/0,5). No se observó un efecto sinérgico entre el AT y la GA. Se encontró que la variación en la formulación del AP con AT y GA influyó en la actividad antimicrobiana del producto obtenido.The design of active biodegradable materials and packaging is one of the challenges of society whose purpose is to try to solve the environmental problems that have been generated by plastic waste by developing biodegradable packaging to improve food conservation and extend shelf life. Analyzed the preparation of an ideal mixture using potato starch (PS), tea tree oil (TO), and gum Arabic (GA), obtaining after extrusion and pressing process the thermoplastic biopolymer plates, that were analyzed their antimicrobial properties. Nineteen samples biopolymer with different proportions were produced PS, TO, and GA. The results obtained from PS/GA based biopolymers (60/2) and (70/5) showed increased antimicrobial activities against Gram-positive and negative bacteria, respectively, followed by the PS/TO (60/1) and (70/0.5). No synergistic effect was observed between TO and GA. It was found that the variation in the PS formulation with TO and GA influenced the antimicrobial activity of the obtained product.Convenio-Programa de Doctorado en Ingeniería Química de la Universidad Central del Ecuador (Quito, Ecuador) y la Universidad de Alicante (Alicante, España)

Synthesis, dopaminergic profile, and molecular dynamics calculations of N-aralkyl substituted 2-aminoindans

Brain dopaminergic system has a crucial role in the etiology of several neuropsychiatric disorders, including Parkinson's disease, depression, and schizophrenia. Several dopaminergic drugs are used to treat these pathologies, but many problems are attributed to these therapies. Within this context, the search for new more efficient dopaminergic agents with less adverse effects represents a vast research field. The aim of the present study was to synthesize N-[2-(4,5-dihydroxyphenyl)-methyl-ethyl]-4,5-dihydroxy-2-aminoindan hydrobromide (3), planned to be a dopamine ligand, and to evaluate its dopaminergic action profile. This compound was assayed as a diastereoisomeric mixture in two experimental models: stereotyped behavior (gnaw) and renal urinary response, after central administration. The pharmacological results showed that compound 3 significantly blocked the apomorphine-induced stereotypy and dopamine-induced diuresis and natriuresis in rats. Thus, compound 3 demonstrated an inhibitory effect on dopaminergic-induced behavior and renal action. N-[2-(-Methyl-ethyl)]-4,5-dihydroxy-2-aminoindan hydrobromide (4) was previously reported as an inotropic agent, and in the present work it was also re-evaluated as a diastereoisomeric mixture for its possible central action on the behavior parameters such as stereotypy and dopamine-induced diuresis and natriuresis in rats. Our results indicate that compound 4 produces an agonistic response, possibly through dopaminergic mechanisms. To better understand the experimental results we performed molecular dynamics simulations of two complexes: compound 3/D2DAR (dopamine receptor) and compound 4/D2DAR. The differential binding mode obtained for these complexes could explain the antagonist and agonist activity obtained for compounds 3 and 4, respectively.Fil: Andujar, Sebastian Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis; ArgentinaFil: de Angel, Biagina Migliore. Universidad del Zulia; VenezuelaFil: Charris, Jaime E.. Universidad Central de Venezuela; VenezuelaFil: Israel, Anita. Universidad Central de Venezuela; VenezuelaFil: Suárez Roca, Heberto. Universidad del Zulia; VenezuelaFil: López, Simon E.. Universidad Simon Bolivar; VenezuelaFil: Garrido, Maria R.. Universidad Central de Venezuela; VenezuelaFil: Cabrera, Elvia Victoria. Universidad del Zulia; VenezuelaFil: Visbal, Gonzalo. Instituto Venezolano de Investigaciones Científicas; VenezuelaFil: Rosales, Cecire. Universidad del Zulia; VenezuelaFil: Suvire, Fernando Daniel. Universidad Nacional de San Luis; ArgentinaFil: Enriz, Ricardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis; ArgentinaFil: Angel Guío, Jorge E.. Universidad del Zulia; Venezuel