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Percorrer por autor "Freire, M. Sonia"

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  • Effect of the Extraction Technique and Operational Conditions on the Recovery of Bioactive Compounds from Chestnut (Castanea sativa) Bur and Shell
    Publication . Fernández-Agulló, Adela; Freire, M. Sonia; Antorrena, Gervasio; Pereira, J.A.; González-Álvarez, Julia
    The aim of this work was to study the extraction of phenolic compounds from chestnut bur and shell, both waste products of chestnut processing in the food industry. Two extraction techniques were compared—maceration with solvents and microwaveassisted extraction. The influence of the solvent used (water, 50% MeOH or 50% EtOH) and temperature (25-50-75 C) on extraction yield and extract total phenols content and FRAP, DPPH, and ABTS antioxidant activities was studied. In the conventional extraction, the yield was significantly higher for the bur (8.54–19.58%) than for the shell (2.91–13.27%); however, the shell extracts showed substantially greater properties. The best extract properties were achieved at 75 C using 50% MeOH for the bur and water for the shell and phenolic compounds with demonstrated antioxidant properties, as gallic acid esters of glucose and ellagic acid, were identified in these extracts by RP-HPLC-ESI-TOF. In addition, the aqueous extracts showed ability to inhibit the growth of gram positive and negative bacteria but not fungi. The kinetic of the extraction process was well fitted by the Peleg’s model. The non-conventional microwaveassisted extraction slightly improved the chestnut bur extraction by reducing the extraction time.
    2014Artigo científico Acesso restrito Ver mais
  • Influence of solvent on the antioxidant and antimicrobial properties of walnut (Juglans regia L.) green husk extracts
    Publication . Fernández-Agulló, Adela; Pereira, Etelvina; Freire, M. Sonia; Valentão, Patrícia; Andrade, Paula B.; González-Álvarez, Julia; Pereira, J.A.
    Walnut green husk is an agro-forest waste generated in the walnut (Juglans regia L.) harvest that could be valued as a source of natural compounds with antioxidant and antimicrobial properties. At this respect, the effect of the solvent (water, methanol, ethanol and 50% aqueous solutions of methanol and ethanol) on the extraction yields and extracts bioactive properties was analysed. Total phenols content of the extracts was determined by the Folin–Ciocalteau method. Extract antioxidant activity was evaluated using the reducing power assay and by the ability of the extracts to scavenge the DPPH radical. The scavenging effect of the aqueous extracts on the nitric oxide radical was also evaluated. The highest extraction yield was achieved with water (44.11%) and high bioactive potential was shown by the samples extracted with water/ethanol (1:1) (84.46 mg GAE/g extract; EC50 = 0.95 mg/mL for reducing power and EC50 = 0.33 mg/mL for DPPH assay). All the antioxidant properties analysed showed a concentrationdependent activity. The antimicrobial activity of the aqueous extracts was assessed and showed ability to inhibit the growth of Gram positive bacteria. The results obtained demonstrated the potential of the walnut green husk as an economical source of antioxidant and antimicrobial agents.
    2013Artigo científico Acesso restrito Ver mais