Browsing by Subject "ORAC"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Publication
    Restricted
    Comparative study of the antioxidant capacity of four stilbenes using ORAC, ABTS+, and FRAP Techniques
    (Springer, 2017-03-17) Rodríguez-Bonilla, Pilar; Matencio Durán, Adrián; Gandía Herrero, Fernando; López Nicolás, José Manuel; García Carmona, Francisco; Bioquímica y Biología Molecular "A"
    Researchers use several different analytical techniques, such as ORAC, ABTS·+, or FRAP, for measuring the antioxidant capacity of bioactive compounds. However, many authors do not take into account that these three techniques have different objectives. This contribution reports on the use of two types of tests to evaluate the antioxidant activity of four stilbene tests based first on the hydrogen atom transfer reaction (ORAC method) and the second on the single electron transfer reaction (ABTS·+ and FRAP assays). For the ORAC assay, the greatest antioxidant activity was shown by resveratrol, followed by oxyresveratrol, pterostilbene, and pinosylvin, while in the ABTS.+ assay, the highest antioxidant capacity was presented by oxyresveratrol, followed by resveratrol, pinosylvin, and finally pterostilbene. In the FRAP assay, the reducing activity shown by all the stilbenes was below that obtained for trolox. The role of phenolic hydroxyl groups was studied. The technique used should be selected taking into account the objectives and the conditions of the medium.
  • Thumbnail Image
    Publication
    Restricted
    The use of cyclodextrins as solubility enhancers in the ORAC method may cause interference in the measurement of antioxidant activity
    (Elsevier, 2022-02-26) Navarro Orcajada, Silvia; Rodríguez Bonilla, Pilar; Matencio Durán, Adrián; Conesa Valverde, Irene; López Nicolás, José Manuel; García Carmona, Francisco; Bioquímica y Biología Molecular A
    The ability of cyclodextrins to enhance the water solubility of lipophilic compounds is used to modify the waterbased Oxygen Radical Absorbance Capacity (ORAC) method to measure antioxidant activity in vitro. However, the use of these solubility enhancers may alter fluorescent readings, which has led to contradictory results being described in the literature. The low specificity of these oligosaccharides and their controlled release effect can result in cyclodextrins forming inclusion complexes with other reagents in the assay, changing the kinetics. In this study, the cause of cyclodextrins’ interference in the ORAC method is evaluated through a physicochemical and computational approach. Cyclodextrins showed a clear increase in the fluorescent signal both in the presence and absence of the antioxidant oxyresveratrol, the precise effect being dependent on the type and concentration of cyclodextrin. Although the glucidic nature of cyclodextrins could play a minimal role in this effect, it seems that the main cause was the encapsulation of other substrates in the reaction, fluorescein and AAPH.
  • Thumbnail Image
    Publication
    Open Access
    Winery By-Products as Sources of Bioactive Tryptophan, Serotonin, and Melatonin: Contributions to the Antioxidant Power
    (MDPI, 2023-04-07) Baenas, Nieves; García-Viguera, Cristina; Domínguez-Perles, Raúl; Medina, Sonia; Tecnología de Alimentos, Nutrición y Bromatología
    The amino acid tryptophan and its derived molecules serotonin and melatonin are involved in a wide range of physiological functions that contribute significantly to human health, namely antioxidant, immune-active, and neurological properties. Grapes and wine are a source of these compounds, but their presence in wine by-products remains underexplored. Therefore, the aim of this work was the identification and quantification of tryptophan, serotonin, and melatonin in winery by-products (grape stems, grape pomace, and wine lees) by ultra-high performance liquid chromatography coupled to electrospray ionization and mass spectrometer with triple-quadrupole technology (UHPLC-ESI-QqQ-MS/MS), as well as the evaluation of the extracts obtained (by applying specific extraction conditions for each of them) for their antioxidant and reducing capacity (by three different and complementary methods: FRAP, ABTS•+, and ORAC). Furthermore, correlation analyses were developed to establish the contribution of the different analytes to the total antioxidant activity. The main results obtained pointed out grape stems as the by-product with the highest tryptophan content (96.28 mg/kg dw) and antioxidant capacity (142.86, 166.72, and 363.24 mmol TE/kg dw, FRAP, ABTS•+, and ORAC, respectively), while serotonin and melatonin were the predominant derivatives in grape pomace (0.086 and 0.902 µg/kg dw, respectively). The antioxidant capacity of the standards was also analysed at the concentrations found in the matrices studied. A significant correlation was found between the concentration of the pure tryptophan standard and the antioxidant capacity (ABTS•+, r2 = 0.891 at p < 0.001 (***); FRAP, r2 = 0.885 at p < 0.01 (**); and ORAC, r2 = 0.854 at p < 0.01 (**)). According to these results, winery by-products can be highlighted as valuable materials to be used as novel ingredients containing tryptophan, serotonin, and melatonin, while tryptophan was identified as the most relevant contributor (out of phenolic compounds) to the antioxidant capacity exhibited by wine by-products.