Recovery of polyphenols by extraction and purification technologies from orange and spinach processing residues

Els articles de l'editorial Elsevier es poden consultar en les seves URL: https://doi.org/10.1016/j.jece.2021.105330 i https://doi.org/10.1016/j.scitotenv.2021.149719The residues resulting from orange and spinach processing, composed mainly by peels and seeds; and leaves, respectively, contain relevant amounts of polyphenols, so they can be used as raw material for recovery natural antioxidants. The recovery of polyphenols from orange and spinach residues have been carried out using conventional and innovative technologies. In recent years, a special interest to use environmentally friendly solvents, e.g., water, has been given, which allow the polyphenols extraction from raw material of plant origin. Ethanol and water, are solvents compatible with food, nutraceutical and pharmaceutical applications, suitable for the extraction of polar compounds such as polyphenols. In this thesis, mechanical stirring extraction (MSE) is used as conventional technology; besides, ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE) and pressurized liquid extraction (PLE) are innovative approaches, for the polyphenol extraction from orange and spinach wastes. In the first instance, the orange and spinach wastes were treated with UAE, MAE and PLE, to evaluate the optimization of polyphenol extraction using ethanol as solvent. UAE was selected for the two matrices, due to its simplicity and low cost, among other reasons, which favoring its industrial scaling-up. The best conditions for UAE orange matrix were ethanol/water/HCl in ratio 60/39.9/0.1 (v/v/v) as the solvent at 25 ºC for an extraction time of 30 min, providing 0.4 mg gallic acid equivalent (GAE) per g fresh weight (fw); and for spinach matrix were ethanol/water/HCl in ratio 80/19.9/0.1 (v/v/v) as the solvent at 25 ºC for an extraction time of 30 min, providing 0.82 mg GAE/g fw. However, UAE was compared to MSE, using water as solvent for the lasts technology. The results obtained were that MSE would be more suitable extraction technique since it´s cheaper than UAE. The selected conditions for orange and spinach wastes extraction were 70 ºC, contact time of 15 min, solid/solvent ratio 1:100 and pH 4 without adjustment for orange waste; and 50 ºC, 5 min, 1:50 and pH 6without adjustment, for spinach residue. Under these conditions, the total phenolic content (TPC) was 1 mgGAE/g fw and 0.8 mg GAE/g fw for orange and spinach, respectively. High pressure liquid chromatography (HPLC) was used for characterization of polyphenols, which is preferred for the separation and quantification of polyphenols in agri-food samples. The HPLC technique was also used for the analyzed of the major polyphenols from orange (e.g., 4-hydroxybenzoic acid, hesperidin) and spinach (e.g., ferulic acid, rutin) wastes and for study of the optimal extraction conditions with the aforementioned extraction techniques. The antioxidant activity of the MSE extracts were evaluated using assays based on 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and 2,2`-azino-bis (3-ethylbenzothiazoline-6-sulfonic) acid (ABTS). As a result, extracts rich in polyphenols were obtained, with antioxidant activity of 2.27 mg Trolox equivalent (TE)/g for orange and 0.04 mg TE/g for spinach. In addition, the orange and spinach extracts from MSE, were treated by membrane technology for their purification. It was concluded that the transmembrane flux depended on the feed flow rate for MF, UF, NF and RO. The pre-concentration and concentration efficiency were evaluated in terms of TPC and by polyphenols families (hydroxybenzoic acids (HB), hydroxycinnamic acids (HC) and flavonoids (F)), using HPLC analysis. For the orange and spinach matrices, MF could be used for extract clarification; NF could be use for pre-concentrate polyphenols; and RO membranes could be used for concentrate polyphenols. Finally, a review was made focused on the antiviral properties of some polyphenols and their mechanism of action against various types of viruses.Los residuos resultantes del procesamiento de naranjas y espinacas, compuestos principalmente por piel y semillas; y hojas, respectivamente, contienen cantidades relevantes de polifenoles, por lo que pueden ser utilizados como materia prima para la recuperación de antioxidantes naturales. La recuperación de polifenoles a partir de residuos de naranja y espinaca se ha llevado a cabo utilizando tecnologías convencionales e innovadoras. El etanol y el agua, son disolventes compatibles con aplicaciones alimentarias, nutracéuticas y farmacéuticas, aptos para la extracción de compuestos polares como los polifenoles. En esta tesis se utiliza como tecnología convencional la extracción con agitación mecánica (MSE); además, la extracción asistida por ultrasonidos (UAE), la extracción asistida por microondas (MAE) y la extracción con líquidos presurizados (PLE) son enfoques innovadores para la extracción de polifenoles usando etanol como solvente. UAE fue seleccionada para las dos matrices, debido a su sencillez y bajo costo, entre otras razones que favorecen su escalamiento industrial. Las mejores condiciones para la matriz de naranja con UAE fueron etanol/agua/HCl en proporción 60/39,9/0,1 (v/v/v) como solvente a 25 ºC por un tiempo de extracción de 30 min, proporcionando 0,4 mg de ácido gálico equivalente (GAE) por gramo de peso fresco (fw); y para la matrix de espinaca fueron etanol/agua/HCl en proporción 80/19,9/0,1 (v/v/v) como solvente a 25 ºC por un tiempo de extracción de 30 min, proporcionando 0,82 mg GAE/G fw. Sin embargo, se comparó UAE con MSE, utilizando agua como solvente para la última tecnología. Los resultados obtenidos fueron que MSE sería la técnica de extracción más adecuada ya que es más económica que UAE. Las condiciones seleccionadas para la extracción de los residuos de naranja y espinaca fueron 70 ºC, tiempo de contacto de 15 min, relación sólido/solvente 1:100 y pH 4 sin ajuste para el residuo de naranja; y 50 ºC, 5 min, 1:50 y pH 6 sin ajuste, para el residuo de espinaca. Bajo estas condiciones, el contenido fenólico total (TPC) fue de 1 mg GAE/g fw y 0,8 mg GAE/g fw para naranja y espinaca, respectivamente. Para la caracterización de polifenoles se utilizó cromatografía líquida de alta presión (HPLC). La técnica de HPLC también se utilizó para el análisis de los principales polifenoles de los desechos de naranja (por ejemplo, ácido 4-hidroxibenzoico, hesperidina) y espinaca (por ejemplo, ácido ferúlico, rutina) y para el estudio de las condiciones óptimas de extracción con las técnicas de extracción antes mencionadas. La actividad antioxidante de los extractos de MSE se evaluó mediante ensayos basados en 2,2-difenil-1-picrilhidrazilo (DPPH), poder antioxidante reductor férrico (FRAP) y ácido 2,2`-azino-bis (3-etilbenzotiazolina-6sulfónico) (ABTS). Como resultado se obtuvieron extractos ricos en polifenoles, con actividad antioxidante de 2,27 mg Trolox equivalente (TE)/g para naranja y 0,4 mg TE/g para espinaca. Además, los extractos de naranja y espinaca de MSE, fueron tratados mediante tecnología de membranas para su purificación. Se concluyó que el flujo transmembrana dependía del caudal de alimentación para MF, UF, NF y OI. La recuperación y la eficiencia de la concentración se evaluaron en términos de TPC y por familias de polifenoles (ácidos hidroxibenzoicos, ácidos hidroxicinámicos y flavonoides), mediante análisis HPLC. Para las matrices de naranja y espinaca, se podría utilizar MF para la clarificación del extracto; NF podría usarse para preconcentrar polifenoles; y las membranas de OI podrían usarse para concentrar polifenoles. Finalmente, se realizó una revisión bibliográfica enfocada en las propiedades antivirales de algunos polifenoles y su mecanismo de acción frente a diferentes tipos de virus.Postprint (published version

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 purposesPeer ReviewedPostprint (published version

A green approach to phenolic compounds recovery from olive mill and winery wastes

The aim of this study was to evaluate the recovery of phenolic compounds from olive mill and winery wastes by conventional solid-liquid extraction (SLE) using water as the extraction solvent. The studied variables were extraction time (5–15 min), temperature (25–90 °C), solid-to-liquid ratio (1:10–1:100 (kg/L)), pH (3-10) and application of multiple extractions (1–3). The extraction efficiency was evaluated in terms of total phenolic content (TPC), determined by high performance liquid chromatography (HPLC-UV), but also from the recovery of some representative phenolic compounds. The optimized conditions were one extraction step, 10 min, 25 °C, 1:30 (kg/L), pH 5 for olive pomace, and one extraction step, 10 min, 70 °C, 1:100 (kg/L), pH 5 for winery residues. The extraction method is simple and suitable for scaling-up in industry, and the aqueous extracts are fully compatible with further purification schemes based on the use of membranes or resins. The optimized technique was applied to a set of different representative residues from olive mill and winery industries, to assess their suitability as sources for phenolic compounds recovery. The phenolic content in the extracts was evaluated by chromatographic analysis and by the Folin–Ciocalteu assay (FC). Furthermore, the antioxidant capacity was determined by 2,2-azinobis-3-etilbenzotiazolina-6-sulfonat (ABTS), 2,-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays. Because of their high contents in phenolic compounds and great antioxidant capacity, olive pomace and lees filters were identified as especially suited sources for phenolic compounds recovery.Peer ReviewedPostprint (published version

Polyphenols and their potential role to fight viral diseases: An overview

Fruits, vegetables, spices, and herbs are a potential source of phenolic acids and polyphenols. These compounds are known as natural by-products or secondary metabolites of plants, which are present in the daily diet and provide important benefits to the human body such as antioxidant, anti-inflammatory, anticancer, anti-allergic, antihypertensive and antiviral properties, among others. Plentiful evidence has been provided on the great potential of polyphenols against different viruses that cause widespread health problems. As a result, this review focuses on the potential antiviral properties of some polyphenols and their action mechanism against various types of viruses such as coronaviruses, influenza, herpes simplex, dengue fever, and rotavirus, among others. Also, it is important to highlight the relationship between antiviral and antioxidant activities that can contribute to the protection of cells and tissues of the human body. The wide variety of action mechanisms of antiviral agents, such as polyphenols, against viral infections could be applied as a treatment or prevention strategy; but at the same time, antiviral polyphenols could be used to produce natural antiviral drugs. A recent example of an antiviral polyphenol application deals with the use of hesperidin extracted from Citrus sinensis. The action mechanism of hesperidin relies on its binding to the key entry or spike protein of SARS-CoV-2. Finally, the extraction, purification and recovery of polyphenols with potential antiviral activity, which are essential for virus replication and infection without side-effects, have been critically reviewed.Peer ReviewedPostprint (author's final draft