Recovery of Anthocyanins Using Membrane Technologies: A Review

Construction of a Biomimetic Receptor Based on Hydrophilic Multifunctional Monomer Covalent Organic Framework Molecularly Imprinted Polymers for Molecular Recognition of Cyanidin-3-O-Glucoside

Anthocyanins (AOCs) are phenols that are readily soluble in water and are commonly present in plants. The chemical instability of AOC, however, causes it to be severely limited in terms of extraction and purification. Hence, in order to obtain efficient and stable extraction of AOC, we designed hydrophilic multifunctional monomer covalent organic framework molecularly imprinted polymers (HMCMIPs) as adsorbents. The functional reagent, p-aminobenzenesulfonic acid (ASA), was added to this material during synthesis to facilitate the sulfonation modification of covalent organic frameworks (COFs), which enhanced its affinity for hydrophilic guests (cyanidin-3-O-glucoside, the representative nutritional and functional ingredient in AOC). With ASA serving as a terminator, overextension of the material to form micron-level cross-linked structures is prevented, thereby increasing its surface area and mass transfer efficiency. The biomimetic receptors were then created by integrating MIPs into sulfonated COFs in order to create multiple binding sites specific for C3G recognition. HMCMIPs exhibited excellent adsorption capacity (1566 mg/g) and superior selectivity (selectivity coefficient >12) for C3G. It has been demonstrated that high purity (93.72%) C3G can be obtained rapidly and efficiently by utilizing HMCMIPs. There may be a potential benefit to the synthesis strategy of HMCMIPs for the extraction of specific active ingredients in the future.

Selective separation of chlorophyll-a using recyclable hybrids based on Zn-MOF@cellulosic fibers

Chlorophyll-a as pigments, exist in the green organelles for plants that act in photosynthesis. Different studies were considered with demonstration of an effective separation technique of Chlorophyll-a without decomposition; however, the reported methods were disadvantageous with expensiveness and low quantum yield. The current work uniquely represents an investigative method for the separation of Chlorophyll-a from spinach extract using cellulosic hybrids based on ZIF-8 @cellulosic fibers (Zn-zeolitic imidazolate frameworks@cellulosic fibers) as a cost effective and recyclable absorbents. To obtain hybrids, ZIF-8 was in-situ prepared over the cellulosic fibers (bamboo, modal and cotton). The untreated and treated fibers were well characterized via FTIR, SEM, EDX, XRD, in order to approve the successive impregnation of ZIF-8. Whereas, the microscopic images showed that, microcrystalline ZIF-8 rods with length of 1.3-4.4 µm were grown over the cellulosic fibers. The obtained hybrids and the untreated fibers were exploited in the separation of Chlorophyll-a via the adsorption/desorption process. The chlorophyll-adsorption was followed Langmuir isotherm and pseudo-second order model. The Langmuir maximum capacities of Chlorophyll-a onto hybrids were followed the order of ZIF-8@cotton (583.6 mg/g) > ZIF-8@modal (561.3 mg/g) > ZIF-8@bamboo (528.7 mg/g). After incorporation of ZIF-8, the maximum adsorption capacities of cellulosic fibers were enhanced by 1.4-1.9 times. Adsorption of chlorophyll onto the applied hybrids was lowered by 27-28%, after five repetitive washing cycles. The data summarized that; chlorophyll was effectively separated by the synthesized ZIF-8@cellulosic fibers hybrids, whereas, the prepared hybrids showed good reusability for application on wider scaled purposes.

Influence of Centrifugation and Transmembrane Treatment on Determination of Polyphenols and Antioxidant Ability for Sea Buckthorn Juice

When the total phenolic content (TPC) and antioxidant activity of sea buckthorn juice were assayed by spectrophotometry, the reaction solutions were not clarified, so centrifugation or membrane treatment was needed before determination. In order to find a suitable method for determining TPC and antioxidant activity, the effects of centrifugation and nylon membrane treatment on the determination of TPC and antioxidant activity in sea buckthorn juice were studied. TPC was determined by the Folin-Ciocalteau method, and antioxidant activity was determined by DPPH, ABTS, and FRAP assays. For Treatment Method (C): the sample was centrifuged for 10 min at 10,000 rpm and the supernatant was taken for analysis. Method (CF): The sample was centrifuged for 10 min at 4000 rpm, filtered by Nylon 66 filtration membranes with pore size of 0.22 μm, and taken for analysis. Method (F): the sample was filtered by Nylon 66 filtration membranes with pore size of 0.22 μm and taken for analysis. Method (N): after the sample of ultrasonic extract solution reacted completely with the assay system, the reaction solution was filtered by Nylon 66 filtration membranes with pore size of 0.22 μm and colorimetric determination was performed. The results showed that centrifugation or transmembrane treatment could affect the determination of TPC and antioxidant activity of sea buckthorn juice. There was no significant difference (p > 0.05) between methods (CF) and (F), while there was a significant difference (p < 0.05) between methods (C) (F) (N) or (C) (CF) (N). The TPC and antioxidant activity of sea buckthorn juice determined by the four treatment methods showed the same trend with fermentation time, and the TPC and antioxidant activity showed a significant positive correlation (p < 0.05). The highest TPC or antioxidant activity measured by method (N) indicates that method (N) has the least loss of TPC or antioxidant activity, and it is recommended for sample assays.

Grape Seed Proanthocyanidins Exert a Radioprotective Effect on the Testes and Intestines Through Antioxidant Effects and Inhibition of MAPK Signal Pathways

The testes and intestines are highly sensitive to ionizing radiation. Low-dose radiation can cause infertility and enteritis. However, there is a lack of safe and efficient radioprotective agents. This study aims to investigate the radioprotective effects of grape seed proanthocyanidins (GSPs) on testicular and intestinal damage induced by ionizing radiation. In vitro, GSPs reduced the apoptosis and proliferation inhibition of mouse testicular stromal cells TM3 and human small intestinal crypt epithelial cells HIEC induced by ionizing radiation, and alleviated DNA double-strand breaks. In vivo, GSPs ameliorated the pathological damage of the testes and intestines induced by ionizing radiation, and protected the endocrine function of the testes and the barrier function of the intestines. In addition, we preliminarily proved that the radioprotective effect of GSPs is related to its antioxidant effect and inhibition of MAPK signaling pathways. Our results indicate that GSPs are expected to be a safe and effective radioprotective drug.

The isolation of water-soluble natural products - challenges, strategies and perspectives

Covering period: up to 2019Water-soluble natural products constitute a relevant group of secondary metabolites notably known for presenting potent biological activities. Examples are aminoglycosides, β-lactam antibiotics, saponins of both terrestrial and marine origin, and marine toxins. Although extensively investigated in the past, particularly during the golden age of antibiotics, hydrophilic fractions have been less scrutinized during the last few decades. This review addresses the possible reasons on why water-soluble metabolites are now under investigated and describes approaches and strategies for the isolation of these natural compounds. It presents examples of several classes of hydrosoluble natural products and how they have been isolated. Novel stationary phases and chromatography techniques are also reviewed, providing a perspective towards a renaissance in the investigation of water-soluble natural products.

Grape Seed Proanthocyanidins play the roles of radioprotection on Normal Lung and radiosensitization on Lung Cancer via differential regulation of the MAPK Signaling Pathway

Radiation-induced lung injury (RILI) is a common serious complication and dose-limiting factor caused by radiotherapy for lung cancer. This study was to investigate radioprotective effects of grape seed proanthocyanidins (GSP) on normal lung as well as radiosensitizing effects on lung cancer. In vitro, we demonstrated radioprotective effects of GSP on normal alveolar epithelial cells (MLE-12 and BEAS/2B) and radiosensitizing effects on lung cancer cells (LLC and A549). In vivo, we confirmed these two-way effects in tumor-bearing mice. The results showed that GSP inhibited tumor growth, and played a synergistic killing effect with radiotherapy on lung cancer. Meanwhile, GSP reduced radiation damage to normal lung tissues. The two-way effects related to the differential regulation of the MAPK signaling pathway by GSP on normal lung and lung cancer. Moreover, GSP regulated secretion of cytokines IL-6 and IFN-γ and expression of p53 and Ki67 on normal lung and lung cancer. Our findings suggest that GSP is expected to be an ideal radioprotective drug for lung cancer patients who are treated with radiotherapy.

Bioactive Compounds from Jambolan (Syzygium cumini (L.)) Extract Concentrated by Ultra- and Nanofiltration: a Potential Natural Antioxidant for Food

Jambolan is an unexplored fruit rich in bioactive compounds like anthocyanins, catechin, and gallic acid. Thus, the extraction of bioactive compounds allows adding value to the fruit. In this context, the present study reports the recovery and concentration of jambolan fruit extract by ultra and nanofiltration for the first time. Acidified water was used to extract polyphenols from the pulp and peel of jambolan. The extracts were concentrated using ultrafiltration and nanofiltration membranes with nominal molecular weight cut-off ranging from 180 to 4000 g mol^-1. Total monomeric anthocyanin, total phenolic compounds, and antioxidant capacity were analyzed. Phenolic compounds were quantified, and anthocyanins were identified by high-performance liquid chromatography coupled to diode-array detection and mass spectrometry (HPLC-DAD-MS). Concentration factors higher than 4.0 were obtained for anthocyanins, gallic acid, and catechin after nanofiltration of the extracts. Other compounds such as epicatechin, p-Coumaric acid, and ferulic acid were quantified in the concentrated extract, and the main anthocyanins identified were 3,5-diglucoside: petunidin, malvidin, and delphinidin. Therefore, jambolan extract showed a high potential to be used as a natural dye and antioxidant in food products.

Adsorption of Anthocyanins by Cation and Anion Exchange Resins with Aromatic and Aliphatic Polymer Matrices

This study examines the mechanisms of adsorption of anthocyanins from model aqueous solutions at pH values of 3, 6, and 9 by ion-exchange resins making the main component of heterogeneous ion-exchange membranes. This is the first report demonstrating that the pH of the internal solution of a KU-2-8 aromatic cation-exchange resin is 2-3 units lower than the pH of the external bathing anthocyanin-containing solution, and the pH of the internal solution of some anion-exchange resins with an aromatic (AV-17-8, AV-17-2P) or aliphatic (EDE-10P) matrix is 2-4 units higher than the pH of the external solution. This pH shift is caused by the Donnan exclusion of hydroxyl ions (in the KU-2-8 resin) or protons (in the AV-17-8, AV-17-2P, and EDE-10P resins). The most significant pH shift is observed for the EDE-10P resin, which has the highest ion-exchange capacity causing the highest Donnan exclusion. Due to the pH shift, the electric charge of anthocyanin inside an ion-exchange resin differs from its charge in the external solution. At pH 6, the external solution contains uncharged anthocyanin molecules. However, in the AV-17-8 and AV-17-2P resins, the anthocyanins are present as singly charged anions, while in the EDE-10P resin, they are in the form of doubly charged anions. Due to the electrostatic interactions of these anions with the positively charged fixed groups of anion-exchange resins, the adsorption capacities of AV-17-8, AV-17-2P, and EDE-10P were higher than expected. It was established that the electrostatic interactions of anthocyanins with the charged fixed groups increase the adsorption capacity of the aromatic resin by a factor of 1.8-2.5 compared to the adsorption caused by the π-π (stacking) interactions. These results provide new insights into the fouling mechanism of ion-exchange materials by polyphenols; they can help develop strategies for membrane cleaning and for extracting anthocyanins from juices and wine using ion-exchange resins and membranes.

Partial Fluxes of Phosphoric Acid Anions through Anion-Exchange Membranes in the Course of NaH2PO4 Solution Electrodialysis

Electrodialysis (ED) with ion-exchange membranes is a promising method for the extraction of phosphates from municipal and other wastewater in order to obtain cheap mineral fertilizers. Phosphorus is transported through an anion-exchange membrane (AEM) by anions of phosphoric acid. However, which phosphoric acid anions carry the phosphorus in the membrane and the boundary solution, that is, the mechanism of phosphorus transport, is not yet clear. Some authors report an unexpectedly low current efficiency of this process and high energy consumption. In this paper, we report the partial currents of H2PO4-, HPO42-, and PO43- through Neosepta AMX and Fujifilm AEM Type X membranes, as well as the partial currents of H2PO4- and H+ ions through a depleted diffusion layer of a 0.02 M NaH2PO4 feed solution measured as functions of the applied potential difference across the membrane under study. It was shown that the fraction of the current transported by anions through AEMs depend on the total current density/potential difference. This was due to the fact that the pH of the internal solution in the membrane increases with the growing current due to the increasing concentration polarization (a lower electrolyte concentration at the membrane surface leads to higher pH shift in the membrane). The HPO42- ions contributed to the charge transfer even when a low current passed through the membrane; with an increasing current, the contribution of the HPO42- ions grew, and when the current was about 2.5 ilimLev (ilimLev was the theoretical limiting current density), the PO43- ions started to carry the charge through the membrane. However, in the feed solution, the pH was 4.6 and only H2PO4- ions were present. When H2PO4- ions entered the membrane, a part of them transformed into doubly and triply charged anions; the H+ ions were released in this transformation and returned to the depleted diffusion layer. Thus, the phosphorus total flux, jP (equal to the sum of the fluxes of all phosphorus-bearing species) was limited by the H2PO4- transport from the bulk of feed solution to the membrane surface. The value of jP was close to ilimLev/F (F is the Faraday constant). A slight excess of jP over ilimLev/F was observed, which is due to the electroconvection and exaltation effects. The visualization showed that electroconvection in the studied systems was essentially weaker than in systems with strong electrolytes, such as NaCl.

Identification and characterization of WD40 superfamily genes in peach

The WD40 transcription factor family is a superfamily found in all eukaryotes that plays important roles in regulating growth and development. To our knowledge, to date, WD40 superfamily genes have been identified and characterized in several plant species, but little information is available on the WD40 superfamily genes in peach. In this study, we identified 220 members of the WD40 superfamily in the peach genome, and these members were further classified into five subfamilies based on phylogenetic comparison with those in Arabidopsis. The members within each subfamily had conserved motifs and gene structures. The WD40 genes were unevenly distributed on chromosomes 1 to 8 of the peach genome. Additionally, 58 pairs of paralog WD40 members were found on eight chromosomes in peach, and 242 pairs of orthologous WD40 genes in peach and Arabidopsis were matched. The 54 selected putative WD40 genes in peach had diverse expression patterns in red-fleshed and white-fleshed peach fruits at five developmental stages. Prupe.6G211800.1 was located only on the cytomembrane, while Prupe.1G428200.1 and Prupe.I003200.1 were located on both the cytomembrane and in the nucleus; Prupe.1G558700.1 was densely localized around the nuclear rim but relatively faintly localized in the nucleoplasm; Prupe.5G116300.1 was located in the nucleus and cytomembrane with strong signals but showed weak signals in the cytoplasm; and Prupe.8G212400.1 and Prupe.1G053600.1 were located mainly in the nuclear envelope and cytomembrane but relatively faintly in the nucleoplasm. This study provides a foundation for the further functional verification of WD40 genes in peach.

Membrane-based technologies for meeting the recovery of biologically active compounds from foods and their by-products

To date, according to the latest literature inputs, membranes-based technologies (microfiltration, ultrafiltration and nanofiltration) have demonstrated to meet the recovery of biologically active compounds, mainly phenolic compounds and their derivatives, from agro-food products and by-products. The goal of this paper is to provide a critical overview of the on ongoing development works aimed at improving the separation, fractionation and concentration of phenolic compounds and their derivatives from their original sources. The literature data are analyzed and discussed in relation to separation processes, molecule properties, membrane characteristics and key factors affecting the performance of such technologies. Technological advances and improvements over conventional technologies, as well as critical aspects to be further investigated are highlighted and discussed. Finally, a critical outlook about the current status for a large-scale application and the role of these processes from an environmental viewpoint is provided.