Review on Extraction of Phenolic Compounds from Natural Sources Using Green Deep Eutectic Solvents

Sustainable green extraction of anthocyanins and carotenoids using deep eutectic solvents (DES): A review of recent developments

Recently, deep eutectic solvents (DES) have been extensively researched as a more biocompatible and efficient alternative to conventional solvents for extracting pigments from natural resources. The efficiency of DES extraction for the anthocyanin and carotenoid can be enhanced by microwave-assisted extraction (MAE) and/or ultrasound-assisted extraction (UAE) techniques. Apart from the extraction efficiency, the toxicity and recovery of the pigments and their bioavailability are crucial for potential applications. A plethora of studies have explored the extraction efficiency, toxicity, and recovery of pigments from various natural plant-based matrices using DES. Nevertheless, a detailed review of the deep eutectic solvent extraction of natural pigments has not been reported to date. Additionally, the toxicity, safety, and bioavailability of the extracted pigments, and their potential applications are not thoroughly documented. Therefore, this review is designed to understand the aforementioned concepts in using DES for anthocyanin and carotenoid extraction.

Deep eutectic solvents for the extraction of polyphenols from food plants

Deep Eutectic Solvents (DESs) offer a promising, sustainable alternative for extracting polyphenols from food plants, known for their health benefits. Traditional extraction methods are often costly and involve toxic solvents. This review discusses the basic concepts, preparation techniques, and factors influencing the effective and safe use of DESs in polyphenol extraction. DESs' adaptability allows integration with other green extraction technologies, such as microwave- and ultrasound-assisted extractions, enhancing their efficiency. This adaptability demonstrates the potential of DESs in the sustainable extraction of bioactive compounds. Current research indicates that DESs could play a significant role in the sustainable procurement of these compounds, marking an important advancement in food science research and development. The review underscores DESs as a realistic, eco-friendly alternative in the realm of natural extraction technologies, offering a significant contribution to sustainable practices in food science.

Application and development of foam extraction technology in wastewater treatment: A review

With the advancement of technology, wastewater treatment has become a significant challenge limiting the clean and sustainable development of chemical and metallurgical industries. Foam extraction, based on interfacial separation and mineral flotation, has garnered considerable attention as a wastewater treatment technology due to its unique physicochemical properties. Although considerable excellent accomplishments were reported, there still lacks a comprehensive summary of process features and contaminant removal mechanisms via foam extraction. According to the latest research progresses, the principles and characteristics of foam extraction technology, the classification and application of flotation reagents are systematically summarized in this work. Then comprehensively commented on the application fields and prospects of iterative flotation technology such as ion flotation, adsorption flotation and floating-extraction. The shortcomings and limitations of the current foam extraction technologies were discussed, and the feasible process intensification techniques were highlighted. This review aims to enchance the understanding of the foam extraction mechanism, and provides guidance for the selection appropriate reagents and foam extraction technologies in wastewater treatment.

One-pot extraction of nanocellulose from raw durian husk fiber using carboxylic acid-based deep eutectic solvent with in situ ultrasound assistance

Nanocellulose (CNF) has emerged as a promising alternative to synthetic petroleum-based polymers, but the conventional preparation process involves multiple tedious steps, heavily dependent on chemical input, and proves cost-inefficient. This study presented an, in situ ultrasound-assisted extraction using deep eutectic solvent (DES) based on choline chloride and oxalic acid for more facile production of CNF from raw durian husk fibers. FESEM analysis confirmed the successful extraction of web-like nanofibril structure with width size ranging from 18 to 26 nm. Chemical composition analysis and FTIR revealed the selective removal of lignin and hemicellulose from the raw fiber. As compared to post-ultrasound treatment, in situ ultrasound-assisted extraction consistently outperforms, yielding a higher CNF yield with finer fiber width and significantly reduced lignin content. Integrating this eco-friendly in situ ultrasonication-assisted one-pot extraction method with a 7.5 min interval yielded the highest CNF yield of 58.22 % with minimal lignin content. The superior delignification ability achieved through the proposed in situ ultrasound-assisted protocol surpasses the individual efficacy of DES and ultrasonication processes, neither of which yielded CNF in our experimental setup. This single-step fabrication process significantly reduces chemical usage and streamlines the production steps yielding web-structured CNF that is ideal for sustainable application in membrane and separator.

Deep eutectic solvent pretreatment of cork dust - Effects on biomass composition, phenolic extraction and anaerobic degradability

In this study, phenolic compounds using deep eutectic solvents (DES) were extracted from cork dust, and the biogas production potential of DES-treated cork dust samples was determined. The DES treatment was carried out using choline chloride and formic acid (1:2 M ratio) at various temperatures (90, 110 and 130 °C) and treatment times (20, 40 and 60 min) at a solid-to-solvent ratio of 1:10 g mL-1. The highest total phenolic content (137 mg gallic acid equivalent (GAE) g-1 dry cork dust) was achieved at 110 °C/20 min. The extracts exhibited an antioxidant capacity of up to 56.3 ± 3.1 % 1,1-diphenyl-2-picrylhydazyl (DPPH) inhibition at a dilution rate of 100. DES treatment resulted in minimal sugar solubilization at low temperatures, while approximately 42 % of the xylan fraction in the biomass degraded under severe conditions (e.g., 130 °C/60 min). Catechin, 4-hydroxybenzoic acid and gallic acid were the major phenolics in DES extracts. The biogas yield of DES-treated cork dust increased with treatment severity. The highest biogas yield (115.1mLN gVS-1) was observed at 130 °C/60 min, representing an increase of 125 % compared to the untreated sample. SEM images revealed that the surface structure of the samples became smoother after mild pretreatment and rougher after harsh pretreatment. Compositional and FTIR analyses indicated that a higher biogas formation potential was associated with increased cellulose content in the substrate, which could be attributed to hemicellulose solubilization in the hydrolysate. Overall, DES pretreatment effectively enhanced phenol extraction and anaerobic degradability.

Ultrasound-Assisted Extraction of Phenolic Compounds from Celtuce (Lactuca sativa var. augustana) Leaves Using Natural Deep Eutectic Solvents (NADES): Process Optimization and Extraction Mechanism Research

Natural deep eutectic solvents (NADESs), as emerging green solvents, can efficiently extract natural products from natural resources. However, studies on the extraction of phenolic compounds from celtuce (Lactuca sativa var. augustana) leaves (CLs) by NADESs are still lacking. This study screened the NADES L-proline-lactic acid (Pr-LA), combined it with ultrasound-assisted extraction (UAE) to extract phenolic compounds from CLs, and conducted a comparative study on the extraction effect with traditional extraction solvents. Both SEM and FT-IR confirmed that Pr-LA can enhance the degree of fragmentation of cell structures and improve the extraction rate of phenolic compounds. Molecular dynamics simulation results show that Pr-LA can improve the solubility of phenolic compounds and has stronger hydrogen bonds and van der Waals interactions with phenolic compounds. Single-factor and Box-Behnken experiments optimized the process parameters for the extraction of phenolic compounds from CLs. The second-order kinetic model describes the extraction process of phenolic compounds from CLs under optimal process parameters and provides theoretical guidance for actual industrial production. This study not only provides an efficient and green method for extracting phenolic compounds from CLs but also clarifies the mechanism of improved extraction efficiency, which provides a basis for research on the NADES extraction mechanism.

Artificial neural network optimisation of natural deep eutectic solvent extraction process of Danshen-Gegen and cytotoxicity study

Natural deep eutectic solvents (NaDESs) are environmentally friendly and efficient for the componential extraction of traditional Chinese medicine compared to conventional organic solvents. In this study, NaDES was screened and employed to extract Danshen-Gegen (DG), and the extraction process was optimised by response surface methodology (RSM) and artificial neural networks (ANN) model. Besides, the in vitro security of extracts of DG were evaluated in PC12 cells. As a result, Betaine-Urea (Bet-Ur) was screened as extraction solvent and ANN model was more accurate than RSM model in optimising the extraction parameter. The extraction process optimised by ANN was as follows: 70% NaDES concentration, 80 mg/mL solid to liquid ratio, 67 °C ultrasonic temperature, and 33 min of ultrasonic time. The comprehensive value of extraction yield was 0.7251 ± 0.84%. IC50 of Bet-Ur, NaDES DG extract and aqueous DG extract were 0.15%, 0.3% and 10% (v/v).

Potential application of green extracts rich in phenolics for innovative functional foods: natural deep eutectic solvents as media for isolation of biocompounds from berries

The health-promoting effects of berries have attracted attention due to the possible application of their extracts as functional ingredients in food products. Natural deep eutectic solvents (NADESs) are a new generation of environmentally friendly solvents for the extraction of natural products, and they are green alternatives to organic solvents, and they can improve the solubility, stability, and bioavailability of isolated biocompounds. In this study, an efficient eco-friendly method was used for the extraction of phenolic compounds from different berries: chokeberries, blueberries, and black goji berries with a range of eutectic solvents consisting of hydrogen bond acceptors (HBAs) such as choline chloride, L-proline, L-glycine, and L-lysine and hydrogen bond donors (HBDs) such as malic, citric, tartaric, lactic and succinic acids, glucose and glycerol. The obtained results indicated the ability of NADESs towards selective extraction of phenolics; the eutectic system choline chloride : malic acid showed selective extraction of anthocyanins, while choline chloride : glycerol and choline chloride : urea showed selectivity towards flavonoids and phenolic acids. The methodology for screening of the NADES extraction performance, which included chromatographic profiling via high-performance thin layer chromatography combined with chemometrics and spectrophotometric essays, allowed effective assessment of optimal eutectic solvents for isolation of different groups of phenolics. Great antioxidant and antimicrobial activities of extracts, along with the green nature of eutectic solvents, enable NADES berry extracts to be used as "green-labelled" functional foods or ingredients.

Recent progress in promoting the bioavailability of polyphenols in plant-based foods

Polyphenols are important constituents of plant-based foods, exhibiting a range of beneficial effects. However, many phenolic compounds have low bioavailability because of their low water solubility, chemical instability, food matrix effects, and interactions with other nutrients. This article reviews various methods of improving the bioavailability of polyphenols in plant-based foods, including fermentation, natural deep eutectic solvents, encapsulation technologies, co-crystallization and amorphous solid dispersion systems, and exosome complexes. Several innovative technologies have recently been deployed to improve the bioavailability of phenolic compounds. These technologies may be utilized to increase the healthiness of plant-based foods. Further research is required to better understand the mechanisms of action of these novel approaches and their potential to be used in food production.

Combination of a Deep Eutectic Solvent and Macroporous Resin for Green Recovery of Iridoids, Chlorogenic Acid, and Flavonoids from Eucommia ulmoides Leaves

To increase the effectiveness of using typical biomass waste as a resource, iridoids, chlorogenic acid, and flavonoids from the waste biomass of Eucommia ulmoides leaves (EULs) were extracted by deep eutectic solvents (DESs) in conjunction with macroporous resin. To optimize the extract conditions, the experiment of response surface was employed with the single-factor of DES composition molar ratio, liquid-solid ratio, water percentage, extraction temperature, and extraction time. The findings demonstrated that the theoretical simulated extraction yield of chlorogenic acid (CGA), geniposidic acid (GPA), aucubin (AU), geniposide (GP), rutin (RU), and isoquercetin (IQU) were 42.8, 137.2, 156.7, 5.4, 13.5, and 12.8 mg/g, respectively, under optimal conditions (hydrogen bond donor-hydrogen bond acceptor molar ratio of 1.96, liquid-solid ratio of 28.89 mL/g, water percentage of 38.44%, temperature of 317.36 K, and time of 55.59 min). Then, 12 resins were evaluated for their adsorption and desorption capabilities for the target components, and the HPD950 resin was found to operate at its optimum. Additionally, the HPD950 resin demonstrated significant sustainability and considerable potential in the recyclability test. Finally, the hypoglycemic in vitro, hypolipidemic in vitro, immunomodulatory, and anti-inflammatory effects of EUL extract were evaluated, and the correlation analysis of six active components with biological activity and physicochemical characteristics of DESs by heatmap were discussed. The findings of this study can offer a theoretical foundation for the extraction of valuable components by DESs from waste biomass, as well as specific utility benefits for the creation and development of natural products.

Toxicity test profile for deep eutectic solvents: A detailed review and future prospects

Deep eutectic solvents (DESs) are preferable in terms of starting materials, storage and synthesis, simplicity, and component material affordability. In several industries ranging from chemical, electrochemical, biological, biotechnology, material science, etc., DES has demonstrated remarkable potential. Despite all these accomplishments, the safety issue with DES must be adequately addressed. Different DES interacts with the cellular membranes differently. It is not possible to classify all DES as easily biodegradable. By expanding the current understanding of the toxicity and biodegradation of DES, interactions between organisms and cellular membranes can be linked. The DES toxicity profile varies according to their concentration, the nature of the individual components, and how they interact with living things. Therefore, the results of this review can serve as a baseline for DES development in the future.

Optimizing green approach to enhanced antioxidants from Thai pigmented rice bran using deep eutectic solvent-based ultrasonic-assisted extraction

Deep eutectic solvents (DES) have garnered significant attention as extraction media owing to their commendable attributes of being environmentally sustainable and the inherent adaptability of DES's versatile physical and chemical characteristics. The present study investigated the effects of deep eutectic solvents on the total contents of anthocyanin, phenolic, and flavonoids, as well as the antioxidant activity of Thai pigmented rice bran extract. The optimal extraction parameters for deep eutectic solvent-based ultrasonic-assisted extraction (DES-UAE) were also determined using the response surface methodology (RSM). The optimal conditions for the extraction of anthocyanins and other antioxidants from pigmented rice bran using a deep eutectic solvent were choline chloride: ethylene glycol (Ch:Eg) at a 1:2 ratio, mixed with 20 % water as a solvent. The ultrasonic-assisted extraction (UAE) at 37 kHz of frequency, 50 °C of temperature, 40 min of extraction time, and a 1:6 g/mL of solid-to-solvent ratio yielded a total anthocyanin content of 4.55 ± 0.09 mg C3G/g DW, a total phenolic content of 26.49 ± 0.62 mg GAE/g DW, a total flavonoid content of 6.57 ± 0.55 mg QE/g DW, and a percent inhibition of DPPH radical of 77.83 ± 1.51. By comparing the antioxidant content that was extracted from three cultivars of pigmented rice, it was found that Leum Pua black rice bran provided significantly higher antioxidant content compared to Hom Nin purple rice bran and Mali Dang red rice bran. This research suggests an achievable, eco-friendly, and effective method for preparing high-quality, consumer-safe Thai rice bran as a raw material for nutraceuticals.

Deep eutectic solvents in sample preparation and determination methods of pesticides: Recent advances and future prospects

This review summarizes recent advances of deep eutectic solvents (DESs) in sample preparation and determination methods of pesticides in food, environmental, and biological matrices since 2019. Emphasis is placed on new DES categories and emerging microextraction techniques. The former incorporate hydrophobic deep eutectic solvents, magnetic deep eutectic solvents, and responsive switchable deep eutectic solvents, while the latter mainly include dispersive liquid-liquid microextraction, liquid-liquid microextraction based on in-situ formation/decomposition of DESs, single drop microextraction, hollow fiber-liquid phase microextraction, and solid-phase microextraction. The principles, applications, advantages, and limitations of these microextraction techniques are presented. Besides, the use of DESs in chromatographic separation, electrochemical biosensors, fluorescent sensors, and surface-enhanced Raman spectroscopy are discussed. This review is expected to provide a valuable reference for extracting and detecting pesticides or other hazardous contaminants in the future.

Alternative Assisted Extraction Methods of Phenolic Compounds Using NaDESs

A renewed understanding of eco-friendly principles is moving the industrial sector toward a shift in the utilization of less harmful solvents as a main strategy to improve manufacturing. Green analytical chemistry (GAC) has definitely paved the way for this transition by presenting green solvents to a larger audience. Among the most promising, surely DESs (deep eutectic solvents), NaDESs (natural deep eutectic solvents), HDESs (hydrophobic deep eutectic solvents), and HNaDESs (hydrophobic natural deep eutectic solvents), with their unique features, manifest a wide-range of applications, including their use as a means for the extraction of small bioactive compounds. In examining recent advancements, in this review, we want to focus our attention on some of the most interesting and novel 'solvent-free' extraction techniques, such as microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) in relation to the possibility of better exploiting DESs and NaDESs as plausible extracting solvents of the phenolic compounds (PCs) present in different matrices from olive oil components, such as virgin olive pomace, olive leaves and twigs, virgin and extra virgin olive oil (VOO and EVOO, respectively), and olive cake and olive mill wastewaters (OMWW). Therefore, the status of DESs and NaDESs is shown in terms of their nature, efficacy and selectivity in the extraction of bioactive phytochemicals such as secoiridoids, lignans, phenolic acids and alcohols. Related studies on experimental design and processes' optimization of the most promising DESs/NaDESs are also reviewed. In this framework, an extensive list of relevant works found in the literature is described to consider DESs/NaDESs as a suitable alternative to petrochemicals in cosmetics, pharmaceutical, or food applications.

Recent Progress on Green New Phase Extraction and Preparation of Polyphenols in Edible Oil

With the proposal of replacing toxic solvents with non-toxic solvents in the concept of green chemistry, the development and utilization of new green extraction techniques have become a research hotspot. Phenolic compounds in edible oils have good antioxidant activity, but due to their low content and complex matrix, it is difficult to achieve a high extraction rate in a green and efficient way. This paper reviews the current research status of novel extraction materials in solid-phase extraction, including carbon nanotubes, graphene and metal-organic frameworks, as well as the application of green chemical materials in liquid-phase extraction, including deep eutectic solvents, ionic liquids, supercritical fluids and supramolecular solvents. The aim is to provide a more specific reference for realizing the green and efficient extraction of polyphenolic compounds from edible oils, as well as another possibility for the future research trend of green extraction technology.

A green method to extract rutin from Sophora japonica L

Sophora japonica L. contains high levels of rutin, which has great potential for use in pharmaceutical products for the treatment of diseases related to the cardiovascular and circulatory systems. We proposed a method of extracting rutin from S. japonica by using a green solvent.•Green deep eutectic solvents (DESs) of choline chloride and ethylene glycol (ChCl-Eth) showed the highest extraction efficiency of rutin from S. japonica.•Under optimal conditions, the extraction yield of ChCl-Eth was 1.34 times higher than that of methanol as solvent.•Rutin was recovered from the DES extracts using water as the antisolvent with a high recovery yield, and the DESs of ChCl-Eth could be productively recovered and reused at least 3 times.

A kinetic study of ex-situ soil remediation by nickel extraction using natural deep eutectic solvent

Using natural deep eutectic solvents (NADESs) as a green reagent is a step toward producing environmentally friendly and sustainable technology. This study screened three natural DESs developed using quaternary ammonium salt and organic acid to analyse their capability to extract nickel ions from contaminated mangrove soil, which are ChCl: Acetic Acid (ChCl-AceA), ChCl: Levulinic Acid (ChCl-LevA), and ChCl: Ethylene Glycol(ChCl-Eg) at molar ratio 1:2. The impact of various operating parameters such as washing agent concentration, pH solution, and contact time on the NADES performance in the dissolution of Ni ions batch experiments were performed. The optimal soil washing conditions for metal removal were 30% and 15% concentration, a 1:5 soil-liquid ratio, and pH 2 of ChCl-LevA and ChCl-AceA, respectively. A single removal washing may remove 70.8% and 70.0% Ni ions from the contaminated soil. The dissolution kinetic of Ni ions extraction onto NADES was explained using the linear kinetic pseudo and intraparticle mass transfer diffusion models. The kinetic validation demonstrates a good fit between the experimental and pseudo-second-order Lagergren data. The model's maximum Ni dissolution capacity, Qe are 51.56 mg g-1 and 52.00 mg g-1 of ChCl-LevA and ChCl-AceA, respectively. The synthesised natural-based DES has the potential to be a cost-effective, efficient, green alternative extractant to conventional solvent extraction of heavy metals.

Subcritical Water Extraction to Valorize Grape Biomass-A Step Closer to Circular Economy

With the increase in the world population, the overexploitation of the planet's natural resources is becoming a worldwide concern. Changes in the way humankind thinks about production and consumption must be undertaken to protect our planet and our way of living. For this change to occur, sustainable development together with a circular economic approach and responsible consumption are key points. Agriculture activities are responsible for more than 10% of the greenhouse gas emissions; moreover, by 2050, it is expected that food production will increase by 60%. The valorization of food waste is therefore of high importance to decrease the environmental footprint of agricultural activities. Fruits and vegetables are wildly consumed worldwide, and grapes are one of the main producers of greenhouse gases. Grape biomass is rich in bioactive compounds that can be used for the food, pharmaceutical and cosmetic industries, and their extraction from this food residue has been the target of several studies. Among the extraction techniques used for the recovery of bioactive compounds from food waste, subcritical water extraction (SWE) has been the least explored. SWE has several advantages over other extraction techniques such as microwave and ultrasound extraction, allowing high yields with the use of only water as the solvent. Therefore, it can be considered a green extraction method following two of the principles of green chemistry: the use of less hazardous synthesis (principle number 3) and the use of safer solvents and auxiliaries (principle number 5). In addition, two of the green extraction principles for natural products are also followed: the use of alternative solvents or water (principle number 2) and the use of a reduced, robust, controlled and safe unit operation (principle number 5). This review is an overview of the extraction process using the SWE of grape biomass in a perspective of the circular economy through valorization of the bioactive compounds extracted. Future perspectives applied to the SWE are also discussed, as well as its ability to be a green extraction technique.

Recovery and repurposing of waste isopropanol with CO2-switchable deep eutectic solvents

Large amounts of waste isopropanol (IPA) are generated in industry, rendering the recovery of IPA highly desirable due to the economic and environmental benefits. Because it forms an azeotropic mixture with water, IPA is difficult to separate from the waste stream. In the present work, a novel CO2-switchable monoethanolamine-butanol deep eutectic solvent (DES) ([MEA][BuOH]) was identified as a superior medium for separating IPA and water at ambient temperature by forming butanol-IPA mixtures. The switchable solvent system combines the advantages of homogeneous and heterogeneous systems, i.e., rapid mixing due to the low mass transfer limitations and facile product separation, respectively. The low viscosity of [MEA][BuOH], the similar physical features (polarity, dipole moment, and dielectric constant) of butanol and IPA, and the H-bonding interactions of [BuOH] with IPA are thought to enable effective IPA capture from water by the butanol. Recovery of the IPA and formation of a butanol-IPA mixture is appealing because the resultant mixture could serve as an additive or substitute for alternative fuels. The results suggest that the developed process will provide a low-cost, energy-saving, effective, and environmentally benign route to recycling and repurposing waste IPA, an environmental hazard, as a potential alternative fuel.

Factors Affecting the Extraction of (Poly)Phenols from Natural Resources Using Deep Eutectic Solvents Combined with Ultrasound-Assisted Extraction

Replacing conventional solvents with deep eutectic solvents (DES) has shown promising effects on the extraction yield of (poly)phenols. DES can be combined with ultrasound-assisted extraction (UAE) to further increase the extraction efficiency of (poly)phenols from natural resources compared to conventional methods. This review discusses the factors associated with DES (composition, solvent-to-sample ratio, extraction duration, and temperature) and UAE (ultrasound frequency, power, intensity, and duty cycle) methods that influence the extraction of (poly)phenols and informs future improvements required in the optimization of the extraction process. For the optimum (poly)phenol extraction from natural resources, the following parameters shall be considered: ultrasound frequency should be in the range of 20-50 kHz, ultrasound intensity in the range of 60-120 W/cm2, ultrasound duty cycle in the range of 40-80%, ultrasound duration for 10-30 minutes, and ultrasound temperature for 25-50 °C. Among the reported DES systems, choline chloride with glycerol or lactic acid, with a solvent-to-sample mass ratio of 10-30:1 shown to be effective. The solvent composition and solvent-to-sample mass ratio should be selected according to the target compound and the source material. However, the high viscosity of DES is among the major limitations. Optimizing these factors can help to increase the yield of extracted (poly)phenols and their applications.

Extraction of Polyphenols from Slovenian Hop (Humulus lupulus L.) Aurora Variety Using Deep Eutectic Solvents: Choice of the Extraction Method vs. Structure of the Solvent

Polyphenols from Slovenian hops (Humulus lupulus L.) of the Aurora variety were extracted by different methods and using classical solvents and several deep eutectic solvents (DES) based on choline chloride as the hydrogen bond acceptor component. The obtained extract solutions were analyzed by HPLC for the content of extracted α- and β-acids and extracted xanthohumol. It was found that choline chloride:phenol DES concentrated aqueous solution had an extraction efficiency close to that of diethyl ether, which is considered one of the best classical extraction solvents for polyphenols from hops. The comparison of the extraction efficiency with other choline chloride-based DESs showed that the chemical similarity of the phenol ring in the solvent DES with the polyphenols in hops may be crucial for a highly efficient extraction with choline chloride:phenol DES. On the other hand, the choice of extraction method and the viscosity of the solvents tested seem to play only a minor role in this respect. As far as we know, this is the first study to attempt to relate extraction efficiency in the extraction of hydrophobic solutes to the compressibility of the DES extractants, the latter of which may be correlated with the extent of hydrophobic hydration around the DES components. In addition, using the heating and stirring method for the preparation of choline chloride-based DES concentrated aqueous solutions we found no support for the occurrence of water in two different roles (in the structural and in the dilution role) in these solvents.

The Most Potent Natural Pharmaceuticals, Cosmetics, and Food Ingredients Isolated from Plants with Deep Eutectic Solvents

There is growing interest in reducing the number of synthetic products or additives and replacing them with natural ones. The pharmaceutical, cosmetic, and food industries are especially focused on natural and bioactive chemicals isolated from plants or microorganisms. The main challenge here is to develop efficient and ecological methods for their isolation. According to the strategies and rules of sustainable development and green chemistry, green solvents and environmentally friendly technologies must be used. The application of deep eutectic solvents as efficient and biodegradable solvents seems to be a promising alternative to traditional methods. They are classified as being green and ecological but, most importantly, very efficient extraction media compared to organic solvents. The aim of this review is to present the recent findings on green extraction, as well as the biological activities and the possible applications of natural plant ingredients, namely, phenolics, flavonoids, terpenes, saponins, and some others. This paper thoroughly reviews modern, ecological, and efficient extraction methods with the use of deep eutectic solvents (DESs). The newest findings, as well as the factors influencing the efficiency of extraction, such as water content, and hydrogen bond donor and acceptor types, as well as the extraction systems, are also discussed. New solutions to the major problem of separating DESs from the extract and for solvent recycling are also presented.

Phenolic compounds extraction by assistive technologies and natural deep eutectic solvents

Phenolic compounds are known to have a significant effect on human defense system due to their anti-inflammatory efficacy. This can slow down the aging process and strengthen the human immune system. With the growing interest in green chemistry concept, extraction of phenolic compounds from plants has been geared towards a sustainable path with the use of green and environmentally friendly solvents such as natural deep eutectic solvents (NADES). This review discusses both the conventional extraction and the advanced extraction methods of phenolic compounds using NADES with focus on microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) techniques ensued by a rationale comparison between them. Employing choline chloride-based natural deep eutectic solvents (NADES) is highlighted as one of the promising strategies in green solvent extraction of phenolic compounds in terms of their biodegradability and extraction mechanism. The review also discusses assistive extraction technologies using NADES for a better understanding of their relationship with extraction efficiency. In addition, the review includes an overview of the challenges of recovering phenolic compounds from NADES after extraction, the potential harmful effects of NADES as well as their future perspective.

Sustainable recovery of phenolic antioxidants from real olive vegetation water with natural hydrophobic eutectic solvents and terpenoids

Olive oil production leads to the generation of olive mill wastewater (OMWW). Due to the presence of phenolic compounds, they are difficult to process, but they represent a source of high-added value chemicals since they have antioxidant and therapeutic properties. This work has studied the extraction of phenolic compounds from a type of OMWW, olive vegetation water, which presents these compounds in a more diluted dosage than in other studied to date, to revalue this waste stream. A real olive vegetation water from a Spanish olive oil producer was used, and liquid-liquid extraction was applied. Terpenoids and terpene-based hydrophobic eutectic solvents were systematically used to extract phenolic compounds following the concentrations of tyrosol, catechol, caffeic acid, and total phenolic content. By molecular simulation with the COSMO-RS method, 4 terpenoids, and 2 eutectic solvents were selected and compared with 2 conventional solvents. The Solvent/Feed ratio in the extraction of phenolic compounds was studied, showing that the solvents with the highest extraction results were geraniol, eucalyptol, and eutectic solvent menthol + camphor, which outperformed conventional solvents methyl isobutyl ketone and diisopropyl ether. Menthol + camphor gave total phenol extraction yields of 88.73% at a Solvent/Feed ratio in volume of 0.50, surpassing all solvents tested. A solvent reuse and regeneration process was applied by back-extraction of the 4 solvents: FTIR results showed the stability of the solvents while maintaining yields in the solvent reuse process. The phenolic compounds could be concentrated in the alkaline phase to factors up to 49.3 to the initial concentration in olive vegetation water. The alkaline phases were neutralized to obtain a precipitate with a caffeic acid content of up to 26 % wt%, and a tyrosol-rich supernatant with a concentration of up to 6.54 g/L. This work proposes a process using natural solvents to extract phenolic compounds from olive vegetation water.

Determination of volatile components in cumin by microwave-assisted PDMS/GO/DES headspace solid phase extraction combined with GC-MS

A novel approach based on polydimethylsiloxane/graphene oxide/deep eutectic solvent (PDMS/GO/DES) sponge headspace solid phase extraction followed by GC-MS was successfully developed to determine the volatile components in cumin. The PDMS/GO/DES exhibits outstanding properties with high adsorption capacity and good chemical stability, and has shown its potentiality as an ideal adsorbent for the extraction of volatile compounds. The influence factors of the extraction process were investigated. Excellent analytical performances were achieved, including wide linearity (0.60-107.72 ng) with high correlation coefficients (R² ≥ 0.9951), low LODs (0.23-9.23 ng) and LOQs (0.54-18.47 ng), satisfactory precision (intra-day RSDs ≤ 2.85% and inter-day RSDs ≤ 3.92%). Under the optimal extraction conditions, the volatile components in 17 cumin samples from four origins in Xinjiang were analyzed and 31 compounds were identified. PCA was used to establish the relationship between the origins and the volatile compounds for further discriminant analysis. The results showed that the PDMS/GO/DES method was a rapid, simple and sensitive technique for the analysis of volatile components in spices.

Extraction, purification, structural characteristics, biological activities, and application of the polysaccharides from Nelumbo nucifera Gaertn. (lotus): A review

Nelumbo nucifera Gaertn. (lotus) is a widely distributed plant with a long history of cultivation and consumption. Almost all parts of the lotus can be used as foodstuff and nourishment, or as an herb. It is noteworthy that the polysaccharides obtained from lotus exhibit surprisingly and satisfying biological activities, which explains the various benefits of lotus to human health, including anti-diabetes, anti-osteoporosis, antioxidant, anti-inflammatory, anti-tumor, etc. Here, we systematically review the recent major studies on extraction and purification methods of polysaccharides from different parts (rhizome, seed, leaf, plumule, receptacle and stamen) of lotus, as well as the characterization of their chemical structure, biological activity and structure-activity relationship, and the applications of lotus polysaccharides in different fields. This article will give an updated and deeper understanding of lotus polysaccharides and provide theoretical basis for their further research and application in human health and manufacture development.

Enhanced Recovery of Natural Antioxidants from Grape Waste Using Natural Eutectic Solvents-Based Microwave-Assisted Extraction

The evaluation of sustainable solvents as alternatives to more harmful conventional solvents combined with intensification techniques to recover phenolic compounds from agri-food waste is in the spotlight. The wine industry generates large amounts of waste as a consequence of grape processing operations, which can be revalued by solvent extraction of valuable antioxidants for food and fine chemical applications. Therefore, the present study focuses on the use of natural eutectic solvents (NAESs) with benign environmental, health, and safety profiles, for valorization of grape waste in the context of a circular economy. Herein, up to 15 NAESs consisting of combinations of three hydrogen bond acceptors (choline chloride, L-proline, and betaine) and four hydrogen bond donors (1,2-propanediol, glycerol, and 1,2- and 1,3-butanediol) were evaluated for antioxidant recovery. After an initial screening of the performance of NAESs by conventional extraction, the process was intensified by microwave-assisted extraction (MAE). The extracts were analyzed by UV/VIS spectrophotometric and HPLC methods. Promising results were obtained with the solvent betaine, 1,2-butanediol [1:4], using MAE at 100 °C for 3 min. Overall, the proposed NAESs-based MAE method was successfully applied to recover target compounds from grape waste, with great prospects for the antioxidants market and sustainable development for the winery sector.

Deep Eutectic Solvents for Biotechnology Applications

Deep eutectic solvents (DESs) are an alternative to traditional organic solvents and ionic liquids and meet the requirements of "green" chemistry. They are easy to prepare using low-cost constituents, are non-toxic and biodegradable. The review analyzes literature on the use of DES in various fields of biotechnology, provides data on the types of DESs, methods for their preparation, and properties. The main areas of using DESs in biotechnology include extraction of physiologically active substances from natural resources, pretreatment of lignocellulosic biomass to improve enzymatic hydrolysis of cellulose, production of bioplastics, as well as a reaction medium for biocatalytic reactions. The aim of this review is to summarize available information on the use of new solvents for biotechnological purposes.

Comparative study of phenolic compounds reveals a positive relationship between astringency and the phenolic composition in table grape varieties

Phenolic compounds and their derivatives play a major role in the intensity and characteristics of grape (Vitis vinifera) astringency. The present study investigated the relationship between phenolic composition and astringency of six commercial table grape varieties (two of each white-, red-, and black-skinned). Qualitative and quantitative liquid chromatography-mass spectrometry analysis was used to identify the variety-specific phenolic profiles in the skins and total astringency intensity was assessed and described by a trained sensory panel. Thirty phenolic compounds were identified among the six varieties. Principal component analysis of the phenolic profiles revealed that the intensity of astringency of grape skin was positively correlated with catechin, epicatechin, epicatechin-3-O-gallate, and proanthocyanidin dimers B1, B2, and B3. A further orthogonal partial least-squares discrimination analysis of these compounds showed that catechin was the substance most strongly and positively correlated (R = 0.904) with grape skin astringency. PRACTICAL APPLICATION: This study provided a better understanding of the relationships between phenolic composition and table grape astringency and highlighted a potential metabolic marker that could be used as a predictor for the complex astringency sensory attributes of table grape berries.

Optimization of ultrasound-assisted extraction of phenolics from Asparagopsis taxiformis with deep eutectic solvent and their characterization by ultra-high-performance liquid chromatography-mass spectrometry

Asparagopsis taxiformis is a significant source of phenolics. Owing to the incessant demand of green extraction procedures for phenolics from A. taxiformis, ultrasound-assisted extraction (UAE) using deep eutectic solvents (DESs) was optimized. Among the tested DESs, betaine-levulinic acid afforded the highest total phenolic content (TPC). Moreover, the optimal extraction conditions elucidated from single-factor and response surface methodologies comprised a 52.41°C ultrasonic temperature, 46.48% water content of DES, and 26.99 ml/g liquid-to-solid ratio. The corresponding TPC (56.27 mg GAE/100 g DW) and antioxidant ability fitted the predicted values. UAE afforded superior TPC and antioxidant abilities with DESs than with traditional solvents. Using UHPLC-MS, seven phenolic acids, 18 flavonoids, and two bromophenols were identified and quantified. DES-UAE afforded the highest phenolic compound number (26) and sum of contents. These results disclose the high extraction efficiency of DES-UAE for A. taxiformis phenolics and provide a basis for the higher-value application of this species.

Applications of Deep Eutectic Solvents in Sample Preparation and Extraction of Organic Molecules

The use of deep eutectic solvents (DES) is on the rise worldwide because of the astounding properties they offer, such as simplicity of synthesis and utilization, low-cost, and environmental friendliness, which can, without a doubt, replace conventional solvents used in heaps. In this review, the focus will be on the usage of DES in extracting a substantial variety of organic compounds from different sample matrices, which not only exhibit great results but surpass the analytical performance of conventional solvents. Moreover, the properties of the most commonly used DES will be summarized.

The Influence of Deep Eutectic Solvents Extract from Ginger on the Formation of Heterocyclic Amines and Advanced Glycation End Products in Roast Beef Patties

Heterocyclic amines (HAs) and advanced glycation end products (AGEs) are important harmful products formed simultaneously during the thermal processing of food. In order to develop a green, efficient method that can be used to control the production of two harmful products simultaneously in food processing. In the present study, deep eutectic solvents (DESs) were used to extract ginger, and this method produced significantly higher levels of total phenolic and flavonoid content as well as an antioxidant activity than ginger extracted using conventional solvents. Herein, we further investigated the inhibitory effects of DES extracts from ginger on the generation of HAs and AGEs in roast beef patties. All the nine DES extracts reduced the formation of HAs and AGEs, and the application of choline chloride–lactic-acid-based DES extract caused a signification reduction of 44.33%, 29.38%, 50.95%, 78.61%, 21.94%, and 17.52% of the PhIP, MeIQx, MeIQ, 4,8-DiMeIQx, Harmane, and Norhamane content, and those for Nε-(carboxymethyl)lysine (CML) and Nε-(carboxyethyl)lysine (CEL) were 49.08% and 58.50%, respectively. Furthermore, the proximate and texture profile changes of beef patties as well as the precursors (creatine, creatinine, and glucose) of HAs and AGEs were evaluated to determine the mechanism of ginger DES extracts on the formation of HAs and AGEs and the physical/chemical changes of ginger DES extracts on beef patties. This study develops a new method for reducing the amount of HAs and AGEs in meat, which will help food manufacturers produce healthier meat products.

Betaine-Based Deep Eutectic Solvent as a New Media for Laccase-Catalyzed Template-Guided Polymerization/Copolymerization of Aniline and 3-Aminobenzoic Acid

Deep eutectic solvents (DESs) can compensate for some of the major drawbacks of traditional organic solvents and ionic liquids and meet all requirements of green chemistry. However, the potential of their use as a medium for biocatalytic reactions has not been adequately studied. In this work we used the DES betaine-glycerol with a molar ratio of 1:2 as co-solvent for enzymatic template-guided polymerization/copolymerization of aniline (ANI) and 3-aminobenzoic acid (3ABA). The laccase from the basidial fungus Trametes hirsuta and air oxygen served as catalyst and oxidant, respectively. Sodium polystyrene sulfonate (PSS) was used as template. Interpolyelectrolyte complexes of homopolymers polyaniline (PANI) and poly(3-aminobenzoic acid) (P3ABA) and copolymer poly(aniline-co-3-aminobenzoic acid) (P(ANI-3ABA)) were prepared and their physico-chemical properties were studied by UV-Vis and FTIR spectroscopy and cyclic voltammetry. According to the results obtained by atomic force microscopy, PANI/PSS had a granular shape, P(ANI-3ABA)/PSS had a spherical shape and P3ABA/PSS had a spindle-like shape. The copolymer showed a greater antimicrobial activity against Escherichia coli and Staphylcocus aureus as compared with the homopolymers. The minimal inhibitory concentration of the P(ANI-3ABA)/PSS against the gram-positive bacterium S. aureus was 0.125 mg mL⁻¹.

Antioxidant Capacity, Vitamin C and Polyphenol Profile Evaluation of a Capsicum chinense By-Product Extract Obtained by Ultrasound Using Eutectic Solvent

Habanero pepper leaves and stems (by-products) have been traditionally considered waste; however, bioactive compounds such as polyphenols, vitamin C and carotenoids have been identified that can be used for formulation of nutraceuticals or functional foods. Furthermore, the extraction of these bioactive compounds by using environmentally friendly methods and solvents is desirable. Thus, the aim of this study was to assess the antioxidant capacity, total polyphenol content (TPC), the phenolic profile and vitamin C content in extracts obtained from by-products (stems and leaves) of two varieties (Mayapan and Jaguar) of habanero pepper by ultrasound-assisted extraction (UAE) using natural deep eutectic solvents (NADES). The results showed that NADES leads to extracts with significantly higher TPC, higher concentrations of individual polyphenols (gallic acid, protocatechuic acid, chlorogenic acid, cinnamic acid, coumaric acid), vitamin C and, finally, higher antioxidant capacity (9.55 ± 0.02 eq mg Trolox/g DM) than UAE extraction performed with methanol as the solvent. The association of individual polyphenols with NADES was confirmed by principal component analysis (PCA). Overall, NADES is an innovative and promising "green" extraction technique that can be applied successfully for the extraction of phenolic compounds from habanero pepper by-products.

Phenolic Compounds' Occurrence in Opuntia Species and Their Role in the Inflammatory Process: A Review

Within the Cactaceae family, Opuntia comprises the most widespread species, with a recognized importance in human life, including feeding, domestic use as home natural barriers, and as a traditional remedy for diverse diseases and conditions such asthma, edema, and burns. Indeed, scientific reports have stated that these health benefits may be due to various active compounds, particularly polyphenols, which are ubiquitously found in plants and have proven their pharmacological efficiency by displaying antimicrobial, anti-cancer, and anti-inflammatory activities, among others. Opuntia species contain different classes of phenolic compounds that are recognized for their anti-inflammatory potential. Among them, quercetin, isorhamnetin, and kaempferol derivates were reported to greatly contribute to modulate cells’ infiltration and secretion of soluble inflammatory mediators, with key implications in the inflammatory process. In this review, we make a summary of the different classes of phenolic compounds reported in Opuntia species so far and explore their implications in the inflammatory process, reported by in vitro and in vivo bioassays, supporting the use of cactus in folk medicine and valorizing them from the socio-economic point of view.

Simultaneous optimization of the extraction process of Yangyin Yiqi Huoxue prescription with natural deep eutectic solvents for optimal extraction yield and antioxidant activity: A comparative study of two models

INTRODUCTION

Natural deep eutectic solvents (NaDESs) are green and effective solvents that are used to extract 3 flavonoids from Yangyin Yiqi Huoxue prescription, a traditional Chinese prescription.

METHODS

A total of 6 types of NaDESs were systematically screened and evaluated for the total extraction yield of puerarin, calycosin, and formononetin by high-performance liquid chromatography. Then, a 4-factor-three-level experimental scheme designed by the Box-Benhnken Design was applied on the basis of a single experiment to determine the extraction yield and the antioxidant property. Finally, the extraction process was optimized through response surface methodology (RSM) and the genetic neural network (GNN), respectively.

RESULTS

The use of betaine-lactic acid as an extractant displayed significant advantages in the screening process. The optimum extraction parameters provided by GNN were as follows: water content 25% (v/v), liquid to material ratio 190 mg/ml, extraction time 37 min, and extraction temperature 63 °C. Under this condition, the average experimental comprehensive evaluation values of the extraction yield and antioxidant properties were 3.12 mg/g and 86.27%, and the relative deviations to the predicted values were 0.30% and 1.44%, respectively. In addition, the experimental results of GNN were better than those of RSM (p < 0.01).

CONCLUSIONS

We found the application of GNN to be effective and credible for bi-objective optimization of extraction yields and antioxidant activity in this study. Moreover, our results provide a reference and a theoretical basis for experimental and future industrial extraction for multi-objective situations.