Exploring the antioxidant features of polyphenols by spectroscopic and electrochemical methods

This paper evaluates the antioxidant ability of polyphenols as a function of their chemical structures. Several common food indexes including Folin-Ciocalteau (FC), ferric reducing antioxidant power (FRAP) and trolox equivalent antioxidant capacity (TEAC) assays were applied to selected polyphenols that di er in the number and position of hydroxyl groups. Voltammetric assays with screen-printed carbon electrodes were also recorded in the range of 0.2 to 0.9 V (vs. Ag/AgCl reference electrode) to investigate the oxidation behavior of these substances. Poor correlations among assays were obtained, meaning that the behavior of each compound varies in response to the di erent methods. However, we undertook a comprehensive study based on principal component analysis that evidenced clear patterns relating the structures of several compounds and their antioxidant activities

Green extraction of antioxidant compounds from olive tree leaves based on naturaldeep eutectic solvents

Agri-food industries generate a large amount of waste that offers great revalorization opportunities within the circular economy framework. In recent years, new methodologies for the extraction of compounds with more eco-friendly solvents have been developed, such as the case of natural deep eutectic solvents (NADES). In this study, a methodology for extracting phenolic compounds from olive tree leaves using NADES has been optimized. The conditions established as the optimal rely on a solvent composed of choline chloride and glycerol at a molar ratio of 1:5 with 30% water. The extraction was carried out at 80 °C for 2 h with constant agitation. The extracts obtained have been analyzed by high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) in MRM mode. The comparison with conventional ethanol/water extraction has shown that NADES, a more environmentally friendly alternative, has improved extraction efficiency. The main polyphenols identified in the NADES extract were Luteolin-7-O-glucoside, Oleuropein, 3-Hydroxytyrosol, Rutin, and Luteolin at the concentrations of 262, 173, 129, 34, and 29 mg kg−1 fresh weight, respectively

Analytical methods for exploring nutraceuticals based on phenolic acids and polyphenols

Phenolic compounds such as phenolic acids, flavonoids, and stilbenes comprise an enormous family of bioactive molecules with a range of positive properties, including antioxidant, antimicrobial or anti-inflammatory effects. As a result, plant extracts are often purified to recover phenolic com-pound enriched fractions to be used to develop nutraceutical products or dietary supplements. In this article, we review the properties of some remarkable plant-based nutraceuticals in which the active molecules are mainly polyphenols and related compounds. Methods for the characterization of these extracts, the chemical determination of the bioactivities of key molecules, and the principal applications of the resulting products will be discussed in detail

Los determinantes del excedente de recursos propios de las entidades españolas

Artículo de revistaA finales de los años sesenta, el sistema financiero español estaba sujeto a una regulación estructural bastante rígida, que se traducía en la imposibilidad para las entidades de fijar libremente los precios, las cantidades o la capacidad productiva. La ausencia de competencia generaba importantes costes para los clientes de activo y pasivo de las entidades, traduciéndose en unas rentas oligopolísticas para las entidades instaladas. La regulación del sistema bancario español no era muy diferente de la que existía, por las mismas fechas, en Europa o, incluso, en Estados Unidos. Así, los tipos de interés, tanto de activo como de pasivo, se fijaban administrativamente, sin que las entidades tuvieran libertad para variarlos. Existían coeficientes de inversión obligatoria que se traducían en una elevada cautividad de los recursos captados por las entidades y en la imposibilidad de invertir en los sectores o proyectos que mayor atractivo ofrecían. Existían, también, limitaciones muy importantes a la apertura de oficinas bancarias, tanto para bancos como para cajas de ahorros. Además, había fuertes restricciones a la entrada de nuevas entidades. El negocio que desarrollaban bancos y cajas difería sustancialmente: los primeros, centrados en empresas; y los segundos, en particulares, normalmente con escaso poder adquisitivo

Total polyphenol content in food samples and nutraceuticals: antioxidant indices versus high performance liquid chromatography

The total content of polyphenols and the antioxidant capacity have been estimated in various food and nutraceutical samples including cranberry, raspberry, artichoke, grapevine, green tea, coffee, turmeric, and other medicinal plant extracts. Samples have been analyzed by using two antioxidant assays ¿ferric reducing antioxidant power (FRAP) and Folin-Ciocalteu (FC)¿ and reversed-phase high-performance liquid chromatography (HPLC) focused on providing compositional fingerprints dealing with polyphenolic compounds. A preliminary data exploration by Principal Component Analysis (PCA) has revealed that HPLC fingerprints are suitable chemical descriptors to classify the analyzed samples according to their nature. Besides, chromatographic data have been correlated with antioxidant data using partial least squares (PLS) regression. Regression models have shown a good prediction capacity to estimate the antioxidant activity from chromatographic data, with determination coefficients (R2) of 0.971 and 0.983 for FRAP and FC assays, respectively

Integration of nanofiltration and reverse osmosis technologies in polyphenols recovery schemes from winery and olive mill wastes by aqueous-based processing.

More sustainable waste management in the winery and olive oil industries has become a major challenge. Therefore, waste valorization to obtain value-added products (e.g., polyphenols) is an efficient alternative that contributes to circular approaches and sustainable environmental protection. In this work, an integration scheme was purposed based on sustainable extraction and membrane separation processes, such as nanofiltration (NF) and reverse osmosis (RO), for the recovery of polyphenols from winery and olive mill wastes. Membrane processes were evaluated in a closed-loop system and with a flat-sheet membrane configuration (NF270, NF90, and Duracid as NF membranes, and BW30LE as RO membrane). The separation and concentration efficiency were evaluated in terms of the total polyphenol content (TPC), and by polyphenol families (hydroxybenzoic acids, hydroxycinnamic acids, and flavonoids), using high-performance liquid chromatography. The water trans-membrane flux was dependent on the trans-membrane pressure for the NF and RO processes. NF90 membrane rejected around 91% of TPC for the lees filters extracts while NF270 membrane rejected about 99% of TPC for the olive pomace extracts. Otherwise, RO membranes rejected more than 99.9% of TPC for both types of agri-food wastes. Hence, NF and RO techniques could be used to obtain polyphenol-rich streams, and clean water for reuse purposes

Integration of membrane processes for the recovery and separation of polyphenols from winery and olive mill wastes using green solvent-based processing

Winery and olive mill industries generate large amounts of wastes causing important environmental problems. The main aim of this work is the evaluation of different membrane separation processes like microfiltration, ultrafiltration, nanofiltration, and reverse osmosis for the recovery of polyphenols from winery and olive mill wastes in aqueous solutions. Membrane processes were tested separately in a closed-loop system, and by an integration in a concentration mode sequential design (open-loop). Feed flow rate was varied from 1 to 10 mL min-1, and permeate samples were taken in order to measure the polyphenols concentration. The separation and concentration efficiency were evaluated in terms of total polyphenol content, and by polyphenols families (hydroxybenzoic acids (HB), hydroxycinnamic acids (HC), and flavonoids (F)), using high performance liquid chromatography. Results showed that MF and UF membranes removed suspended solids and colloids from the extracts. NF was useful for polyphenols separation (HB rejections were lower than for HC and F: HB rejections of 50 and 63% for lees filters and olive pomace extracts, respectively), and RO membranes were able to concentrate polyphenols streams (86 and 95% rejection from lees filters and olive pomace, respectively). Membranes sequential designs for lees filters and olive pomace extracts, using a selective membrane train composed by UF, NF and RO membranes, were able to obtain polyphenol rich streams and high-quality water streams for reuse purposes

Recovery of Polyphenols from Agri-Food By-Products: The Olive Oil and Winery Industries Cases

The production of olive oil and wine are two of the main agri-food economic activities in Southern Europe. They generate large amounts of solid and liquid wastes (e.g., olive pomace, olive mill wastewater, grape pomace, grape stems, wine lees, and wine processing wastewater) that represent a major environmental problem. Consequently, the management of these residues has become a big challenge for these industries, since they are harmful to the environment but rich in bioactive compounds, such as polyphenols. In recent years, the recovery of phenolic compounds has been proposed as a smart strategy for the valorization of these by-products, from a circular economy perspective. This review aims to provide a comprehensive description of the state of the art of techniques available for the analysis, extraction, and purification of polyphenols from the olive mill and winery residues. Thus, the integration and implementation of these techniques could provide a sustainable solution to the olive oil and winery sector

Recovery of added-value compounds from orange and spinach processing residues: green extraction of phenolic compounds and evaluation of antioxidant activity

Phenolic compounds recovery by mechanical stirring extraction (MSE) was studied from orange and spinach wastes using water as a solvent. The statistical analysis showed that the highest total polyphenol content (TPC) yield was obtained using 15 min, 70 °C, 1:100 (w/v) solid/solvent ratio and pH 4 for orange; and 5 min, 50 °C, 1:50 (w/v) solid/solvent ratio and pH 6 for spinach. Under these conditions, the TPC was 1 mg gallic acid equivalent (GAE) g−1 fresh weight (fw) and 0.8 mg GAE g−1 fw for orange and spinach, respectively. MSE substantially increased the phenolic compounds yields (1-fold for orange and 2-fold for spinach) compared with ultrasound-assisted extraction. Furthermore, the antioxidant activity of orange and spinach extracts was evaluated using DPPH, FRAP and ABTS. The obtained results pointed out that the evaluated orange and spinach residues provided extracts with antioxidant activity (2.27 mg TE g−1 and 0.04 mg TE g−1, respectively)

Recovery of natural polyphenols from spinach and orange by-products by pressure-driven membrane processes

Spinach and orange by-products are well recognized for their health benefits due to the presence of natural polyphenols with antioxidant activity. Therefore, the demand to produce functional products containing polyphenols recovered from vegetables and fruits has increased in the last decade. This work aims to use the integrated membrane process for the recovery of polyphenols from spinach and orange wastes, implemented on a laboratory scale. The clarification (microfiltration and ultrafiltration, i.e., MF and UF), pre-concentration (nanofiltration, NF), and concentration (reverse osmosis, RO) of the spinach and orange extracts were performed using membrane technology. Membrane experiments were carried out by collecting 1 mL of the permeate stream after increasing the flow rate in 1 mL/min steps. The separation and concentration factors were determined by HPLC-DAD in terms of total polyphenol content and by polyphenol families: hydroxybenzoic acids, hydroxycinnamic acids, and flavonoids. The results show that the transmembrane flux depended on the feed flow rate for MF, UF, NF, and RO techniques. For the spinach and orange matrices, MF (0.22 μm) could be used to remove suspended solids; UF membranes (30 kDa) for clarification; NF membranes (TFCS) to pre-concentrate; and RO membranes (XLE for spinach and BW30 for orange) to concentrate. A treatment sequence is proposed for the two extracts using a selective membrane train (UF, NF, and RO) to obtain polyphenol-rich streams for food, pharmaceutical, and cosmetic applications, and also to recover clean water streams