Examinando por Autor "Rivera-Tovar, Pamela Raquel"

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    Ítem
    Adsorption of low molecular weight food relevant polyphenols on cross-linked agarose gel
    (Elsevier, 2021-10-25) Rivera-Tovar, Pamela Raquel; Pérez-Manríquez, Javiera; Mariotti-Celis, María Salomé; Escalona, Nestor; Pérez-Correa, José Ricardo
    Adsorption of five relevant low molecular weight polyphenols identified in agro-industrial waste extracts (Aristotelia chilensis leaves, Carménère wine pomace, spent coffee grounds, and brewery waste streams) was measured and characterized. SuperoseTM 12 prep grade and between three and six solutions with different water, ethanol, and acetic acid compositions were used as adsorbent and liquid phases. The chosen adsorbent and liquid phases were relevant for designing an adsorption preparative liquid chromatography (APLC) process to isolate these polyphenols. Langmuir and Freundlich models adequately fitted the obtained isothermal equilibrium data. The Freundlich model represented better ferulic acid (FA), kaempferol (KAE), and resveratrol (RSV) adsorptions, while the Langmuir model represented better gallic acid (GA) and catechin (CAT). Different polyphenol/agarose affinities in water-rich liquid phases were observed. From this, a hypothetical elution order was established (KAE < GA < FA < CAT < RSV), which was partially experimentally corroborated (for a mixture of GA, CAT, and RSV) with an APLC system. Lowering the water proportion or increasing the EtOH:HAc ratio in the liquid phase reduced the adsorption of these polyphenols, except for FA. The decrease in adsorption with temperature and the negative values of ΔH indicated that these processes were exothermic. The adsorption of all the polyphenols was governed by physisorption. All the adsorption processes studied were spontaneous and thermodynamically feasible (ΔG < 0). In addition, the polyphenol molecules were less randomly organized (more ordered) at the polyphenol/agarose interface during the adsorption process (ΔS < 0).
  • Miniatura
    Ítem
    Multi-response optimal hot pressurized liquid recovery of extractable polyphenols from leaves of maqui (Aristotelia chilensis [Mol.] Stuntz)
    (Elsevier, 2021-03-29) Rivera-Tovar, Pamela Raquel; Torres, María Dolores; Camilo, Conrado; Mariotti-Celis, María Salomé; Domínguez, Herminia; Pérez-Correa, José Ricardo
    Multi-response optimization of hot pressurized liquid extraction (HPLE) was applied for the first time to obtain maqui (Aristotelia chilensis [Mol.] Stuntz) leaf extracts. The total polyphenol content (TPC), the antioxidant capacity (AC) as well as the total polyphenol purity of the maqui leaf extracts were accurately predicted (RSD < 8%) at the evaluated extraction scales. The optimum HPLE conditions that prioritized TPC and AC equally (OPT1) recovered ~3 times more TPC (205.14 mg GAE/g leaves) than maqui leaf extracts obtained by maceration, while the extract that prioritized purity over TPC and AC presented the highest purity (36.29%) and an EC50 ~3 times lower than currently reported values. It was found by multi-response optimization that maqui leaves and HPLE are among the best natural sources and extraction techniques, respectively, to recover protocatechuic acid, quercetin, and catechin.