RESUMEN

Resumen: El gel de Aloe vera es considerado una fuente natural de múltiples beneficios, originados por la acción combinada de vitaminas, aminoácidos, compuestos fenólicos, enzimas, minerales, ácidos orgánicos, lípidos y carbohidratos, que se relacionan con la mejora de enfermedades neuro-degenerativas como Alzheimer. Los ensayos in vitro e in silico permiten confirmar e identificar posibles beneficios de esta planta y sus compuestos en enfermedades. El objetivo del presente trabajo fue evaluar la actividad antioxidante del gel de A. vera y mediante análisis in silico, establecer el potencial terapéutico de sus compuestos bioactivos en la enfermedad de Alzheimer. Se obtuvieron hojas de A. vera, de las que se extrajo el gel, retirando el exocarpio, se liofilizó y almacenó hasta su uso. Se caracterizó la capacidad antioxidante, se cuantificaron los compuestos fenólicos y flavonoides y se analizó la relación que existe entre los parámetros mediante correlación de Pearson. Mediante análisis in silico se evaluó el potencial de interacción de 8 compuestos del gel con la proteína gamma secretasa. El gel de A. vera obtuvo alta capacidad antioxidante por ABTS, DPPH, radical OH y poder reductor, usando bajas concentraciones para inhibir el 50 % de los radicales, y correlaciones positivas con fenoles totales y flavonoides. En el estudio in silico el compuesto que presentó mejor unión con gamma secretasa fue aloe-emodina, con menor energía libre de unión y menor concentración de constante de inhibición, sugiriendo su potencial uso como coadyuvante en el tratamiento de la enfermedad de Alzheimer.

Abstract: Aloe vera gel is considered a natural source of multiple benefits, originated by the combined action of vitamins, amino acids, phenolic compounds, enzymes, minerals, organic acids, lipids and carbohydrates, which are related to the improvement of neuro-degenerative diseases such as Alzheimer's. In vitro and in silico tests allow us to confirm and identify possible benefits of this plant and its compounds in diseases. The objective of the present study was to evaluate the antioxidant activity of A. vera gel and, through in silico analysis, to establish the therapeutic potential of its bioactive compounds in Alzheimer's disease. A. vera leaves were obtained, from which the gel was extracted, removing the exocarp, lyophilized and stored until use. The antioxidant capacity was characterized, the phenolic compounds and flavonoids were quantified, and the relationship between the parameters was analyzed using Pearson correlation. The interaction potential of 8 compounds in the gel with the gamma secretase protein was evaluated through in silico analysis. The A. vera gel obtained high antioxidant capacity due to ABTS, DPPH, OH radical and reducing power, using low concentrations to inhibit 50 % of the radicals, and positive correlations with total phenols and flavonoids. In the in silico study, the compound that showed the best binding with gamma secretase was aloe-emodin, with lower binding free energy and lower inhibition constant concentration, suggesting its potential use as an adjuvant in the treatment of Alzheimer's disease.

RESUMEN

RESEARCH BACKGROUND: TomloxB is the main isoform of lipoxygenase associated with ripening and senescence of fruits. On the other hand, ethylene, a gaseous hormone, is essential for the regulation of ripening in climacteric fruits like tomatoes. However, the relationship between TomloxB and ethylene production has not been thoroughly studied. Therefore, we aim to assess the effect of exogenous ethylene in transgenic tomatoes that contain a silenced TomloxB gene, and subsequently evaluate lipoxygenase activity, 1-aminocyclopropane-1-carboxylic acid oxidase and ethylene production; as well as to quantify the expression of the genes encoding 1-aminocyclopropane-1-carboxylic acid oxidase and TomloxB. EXPERIMENTAL APPROACH: To investigate the effect of lipoxygenase and 1-aminocyclopropane-1-carboxylic acid oxidase activity, fruits harvested at the stages of break, turning and pink were used. Tomatoes at break stage collected from transgenic and wild type plants were used to determine ethylene production and gene expression. Genetically modified and wild type tomato fruits were exposed to 100 µL/L exogenous ethylene. Lipoxygenase activity was measured spectrophotometrically. Activity of 1-aminocyclopropane-1-carboxylic acid oxidase and ethylene production were determined by gas chromatography. Oligonucleotides for differentially expressed genes: 1-aminocyclopropane-1-carboxylic acid oxidase and TomloxB were used to determine gene expression by real-time PCR. RESULTS AND CONCLUSIONS: The data showed that silencing of TomloxB caused a reduction in lipoxygenase activity and ethylene production in tomato fruits, and also reduced 1-aminocyclopropane-1-carboxylic acid oxidase activity. Hence, the addition of exogenous ethylene increased lipoxygenase activity in all treatments and 1-aminocyclopropane-1-carboxylic acid oxidase activity only in transgenic lines at break stage, consequently there was a positive regulation between TomloxB and ethylene, as increasing the amount of ethylene increased the activity of lipoxygenase. The results suggest that lipoxygenase may be a regulator of 1-aminocyclopropane-1-carboxylic acid oxidase and production of ethylene at break stage. NOVELTY AND SCIENTIFIC CONTRIBUTION: These results lead to a better understanding of the metabolic contribution of TomloxB in fruit ripening and how it is linked to the senescence-related process, which can lead to a longer shelf life of fruits. Understanding this relationship between lipoxygenase and ethylene can be useful for better post-harvest handling of tomatoes.