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Browsing Capítulos de libros by Subject "Antioxidantes"
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Item Antioxidantes: importancia biológica y métodos para medir su actividad(Corporación Universitaria Lasallista, 2012-03-29) Londoño Londoño, Julián AlbertoResumen La actividad antioxidante es la capacidad de una sustancia para inhibir la degradación oxidativa (por ejemplo, la peroxidación lipídica), de tal manera que un antioxidante actúa, principalmente, gracias a su capacidad para reaccionar con radicales libres y, por lo tanto, recibe el nombre de antioxidante terminador de cadena. Sin embargo, es necesario distinguir también entre actividad estabilizadora de radicales libres o antiradicalaria (en inglés, scavenger) y actividad antioxi -dante. La primera está determinada completamente por la reactividad de un antioxidante frente a radicales libres, lo cual puede ser caracterizado por la velocidad de esa reacción. Por su parte, la segunda mide la ca-pacidad para retardar la degradación oxidativa. Por lo tanto, una alta actividad anti-radicalaria no siempre correlaciona con una alta actividad antioxidante; en particular, algunos compuestos fenólicos sintéticos presentan alta reactividad frente a radicales libres, pero muestran moderada actividad antioxidante. De hecho, hasta ahora, no existen métodos mundialmente unificados para medir capacidad antioxidante, en parte, debido a la disparidad de condiciones en las cuales se desarrollan estas metodologías, además de la complejidad de los sistemas y de la diversidad de ma -trices que necesitan ser evaluadas. En general, el objetivo de este trabajo es presentar una revisión actualizada de los conceptos fundamentales de los antioxidantes, abarcando desde los radicales libres de importancia biológica, hasta los sistemas de defensa antioxidante y los métodos para medir esta actividad.Item Inhibición de la polifenoloxidasa extraída del banano (cavendish) por medio de algunos derivados del isoespintanol(Corporación Universitaria Lasallista, 2012-04-12) Gil Garzón, Maritza Andrea; Rojano, Benjamín Alberto; Guerrero, Carlos AndrésAbstract Introduction. Looking for new sources of natural compounds with anti-oxidant activity, a great variety of phenolic plants have been being found. They have a high protective power on the enzymatic browning, responsible for undesired color changes in fresh fruits and vegetables. Objective. In this work, enzymatic browning inhibition of polyphenol oxidase, PPO, extracted from Giant Cavendish bananas (export type) is studied, by the use of the dopamine substratum. Methodology. The inhibitors used were: Isoespintanol (a metabolite extracted from Oxandra cf. xylopioides (Annonaceae) and two of its analogs: 2-isopropyl-4 -bromo-3 ,6-dimethoxy-5-methylphenol and 3-isopropyl-6-methyl-1, 2,4-trihydroxybenzene, which were simultaneously obtained by the use of the bromination method with dimethylsulphonium bromide in a (75:25) relation, respectively. Also, ascorbic acid was used as a reference anti-oxidant. The compounds synthesized were characterized by performing a magnetic resonance spectroscopy and a chromatography coupled to masses and its anti-oxidant capability was evaluated with the ABTS, FRAP and DPPH methods. PPO´s activity, partially purified, was analyzed on the enzymatic extract, spectrophotometrically, at 30°C before the anti-oxidants at 500, 1000 and 1500 ppm. Results and analysis. Isoespintanol had the best response under the three anti-oxidant capability techniques, while the bromination had the best reduction capability under the FRAP method and the demethylated had a better performance in the methanolic medium. PPO´s activity was 102.3 activity units, this means that thee was a reduction between 72.5 and 92% with al of the compounds. The highest inhibition was achieved at 1500 ppm of ascorbic acid (92%). With the inhibition of the enzymatic activity for the brominated and the demethylated compound there were no significant differences, (P>0.05) at 500 ppm (84.8 – 84.53%), 1000 ppm (73.87 - 72.53%) and 1500 ppm (84 – 82.4%), respectively. The opposite took place for the isoespintanol concerning its two analogs, at 1000 ppm (42.4%), which obtained significant statistic differences (P>0.05). The inhibition type was studied for isoespintanol, which had a competitive inhibition (KI=0.015M y KM=0.026M).