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Browsing by Author "Guetat, Safa"

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  • TocVit: optimization of tocopherols extraction through conventional and emerging techniques, and bioactive characterization of the obtained extracts
    Publication . Guetat, Safa; Carocho, Márcio; Heleno, Sandrina A.; Rjeb, Ines Ben
    Vitamin E, an essential fat-soluble vitamin, is well known for its antioxidant properties, ability to regulate cholesterol levels, among other benefits; Its consumption strengthens the immune system, prevents chronic diseases such as Alzheimer's, and reduces oxidative and inflammatory stress. It is composed of a group of molecules called tocopherols, classified into four isoforms: α-tocopherol, β-tocopherol, γ-tocopherol, and δ-tocopherol, responsible for its various biological activities. It can be found in several dry fruits such as almonds, hazelnuts, peanuts, and pistachios, with walnuts (Juglans regia L.) being one of them, produced in large quantities in Portugal. Vitamin E can be obtained from by-products of the nut industry, promoting the reuse of these matrices to obtain molecules with high added value. However, the extraction of this vitamin can be challenging due to its fragility, making it prone to degradation during the extraction process. Therefore, the present study aims to optimize tocopherol extraction from walnuts using conventional and emerging techniques, as well as to evaluate the obtained extracts from a bioactive perspective. Four different extraction methods, including conventional solvent extraction, soxhlet extraction, microwave-assisted extraction, and ultrasound-assisted extraction, were optimized demonstrating that γ-tocopherol is the most abundant isoform, followed by δ-tocopherol, β-tocopherol and α-tocopherol. The microwave- assisted extraction method stands out as a promising approach for tocopherol extraction from walnuts. It showed the highest efficiency in terms of both tocopherol content 1.060±0.007mg/100g (dry weight) and a quenching radical activity of 0.190±0.04mg/mL using the 2,2-diphenil-1-picrylhydrazil and 2.87±0.03mg/mL for the reducing power. Regarding the antimicrobial potential, UAE stands out in the inhibition of A. fumigatus in a concentration comparable with the one of the positive control ketoconazole. Furthermore, the microwave technique is more environmentally friendly and economical, requiring less solvent and shorter extraction times.
    2024Master thesis Open access Show more