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Percorrer por autor "Cruz, Diana"

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  • DNA-based sensor against nitrite oxide radical: Evaluation of total antioxidant capacity in beverages
    Publication . Cruz, Diana; Barroso, M. Fátima; Ramalhosa, Maria João; Coelho, Andreia; Silva, Hélder da; Duarte, Abel J.; González-García, Maria Begoña; Carvalho, Ana P.; Delerue-Matos, Cristina
    Reactive nitrogen and oxygen species are produced in cells and play an important role in the oxidative metabolism; when in abnormal concentrations, they are able to induce oxidative damage on biomolecules, namely in DNA. In this paper it is described, an electrochemical DNA-based sensor against NOradical dot radical developed for total antioxidant capacity (TAC) evaluation. The sensor consisted on dA20 (adenine-rich oligonucleotide) physically adsorbed into carbon paste electrode (CPE). When this dA20-CPE was damaged, by immersion in a freshly generated NOradical dot radical, a protective effect onto dA20 was observed in the presence of antioxidants (ascorbic, gallic, caffeic, p-coumaric acids). Electrochemical studies were performed through square wave voltammetry. The construction of the sensor is simple, fast and the results indicated that the DNA-based sensor is suitable, accurate, and can be used to the assessment of TAC in commercial samples of juices.
    2016Artigo científico Acesso restrito Ver mais
  • Microwave-assisted extraction in goji berries: effect on composition and bioactivity, evaluated through conventional and nonconventional methodologies
    Publication . Carvalho, Ana P.; Mendes, Marta; Moreira, Manuela M.; Cruz, Diana; Magalhães, Júlia M. C. S.; Barroso, M. Fátima; Ramalhosa, Maria João; Duarte, Abel; Guido, Luís; Gomes, Ana M.; Delerue-Matos, Cristina
    This study aimed to evaluate the effect of microwave-assisted extraction (MAE) parameters on the composition and bioactivity of goji (Lycium barbarum) extracts. Extracts were obtained under a central composite design combination of experimental conditions, and characterised through HPLC-DAD; their bioactive capacity was ascertained for antimicrobial and antioxidant capacity, the later by spectrophotometric [2,2-azinobis (3- ethylbenzothiazoline-6-sulfonic acid) diammonium salt-radical scavenging activity assay – 413–748 mg ascorbic acid equivalents/100 g DW and oxygen radical absorbance capacity – 1901–2292 mg trolox equivalents/100 g DW] and electrochemical (DNA-based sensor – 3571–6602 mg ascorbic acid/100 g DW) methods. The quantitative profile of phenolic compounds was strongly dependent on MAE conditions. Significant correlations were found between the presence of several flavonoids and solvent composition, as well as between phenolic acids with methoxy group and the response to DNA-based sensor. Results may improve targeted extractions for specific compounds, leading to the achievement of extracts richer in antioxidant capacity, as well as in the tailoring of the biosensor response sensitivity to the composition of the extracts under analysis.
    2016Artigo científico Acesso restrito Ver mais