The perspectives of natural deep eutectic solvents in agri-food sector

Supramolecular deep eutectic solvent: a powerful tool for pre-concentration of trace metals in edible oil

The utilization of supramolecular deep eutectic solvent eddy-assisted liquid-liquid microextraction utilizing 2-hydroxypropyl β-cyclodextrin (SUPRADES) has been identified as a successful method for pre-enriching Cu, Zn, and Mn in vegetable oil samples. Determination of each element was conducted by inductively coupled plasma optical emission spectrometry (ICP-OES) after digestion of metal-enriched phases. Various parameters were examined, including the composition of SUPRADES species [2HP-β-CD: DL-lactic acid], a cyclodextrin mass ratio of 20 wt%, a water bath temperature of 75 °C, an extractor volume of 800 μL, a dispersant volume of 50 μL, and an eddy current time of 5 min. Optimal conditions resulted in extraction rates of 99.6% for Cu, 105.2% for Zn, and 101.5% for Mn. The method exhibits a broad linear range spanning from 10 to 20,000 μg L-1, with determination coefficients exceeding 0.99 for all analytes. Enrichment coefficients of 24, 21, and 35 were observed. Limits of detection ranged from 0.89 to 1.30 μg L-1, while limits of quantification ranged from 3.23 to 4.29 μg L-1. The unique structural characteristics of the method enable the successful determination of trace elements in a variety of edible vegetable oils.

Tunable durian seed gum-derived eutectogel as a novel coating material: Rheological, thermal, textural and barrier properties for enhanced food preservation

As a promising green and sustainable coating material, gum was extracted from durian seed to produce eutectogel, which the properties were tunable using natural deep eutectic solvent (NADES). Ten different eutectogels were successfully synthesized using durian seed gum (DSG) and xanthan gum (XG) gelators at different composition (5, 10, 15 %) to gel choline chloride-glucose (1:1), choline chloride-fructose (1:2) and betaine-glucose-water (1:1:1) NADESs. Results revealed that eutectogel was non-Newtonian and weak gel material with excellent thermostability up to 200 °C. When the gum content increased, the resulted eutectogel showed higher viscosity, yield stress, hardness, gumminess, adhesiveness, and weight holding capacity. In overall, choline chloride-fructose (1:2) NADES and 10 % of DSG formed an excellent eutectogel which remained stable and compatible upon 12 weeks of storage. It displayed superior viscoelastic, texture, gases and moisture barrier properties which were beneficial for food coating application. This eutectogel was able to extend the shelf life of fresh-cut apples during storage with lower weight loss and higher total phenolic content (TPC). The potential future of this well-characterized tunable DSG-derived eutectogel includes, but not limited to, food and pharmaceutical industries, smart sensing, flexible wearable electronics, water purification, supercapacitors and batteries.

Valorisation of Raspberry Seeds in Cosmetic Industry-Green Solutions

The fruit processing industry generates large quantities of by-products well known to be rich in bioactive compounds with numerous nutritional properties and beneficial effects for human health. We developed a strategy to valorise raspberry seeds and obtain valuable ingredients with potential application in cosmetic skincare formulas. Cold press extraction technology was applied to extract oil, and the remaining defatted raspberry seed cake was treated with three proline based deep eutectic solvents (DES) to extract polyphenols. The most potent was proline/citric acid extract, with free and total ellagic acid content (52.4 mg/L and 86.4 mg/L), total phenolic content (TPC, 550.1 mg GAE/L) and radical scavenging activity (RSA, 4742.7 mmol TE/L). After the direct mixing of the extract and after encapsulation with starch as a carrier, the skincare emulsion and microemulsion were characterised by irritation potential (Zein test), transepidermal water loss (TEWL), red blood cell (RBC), and DPPH antioxidant test. The resulting preparations were of improved quality in comparison to the control hand cream, with a low skin irritation effect, lower TEWL, and higher antioxidant potential. This work complies with circular economy principles and green technology standards, and represents the efficient model on how to reuse natural resources through waste minimization.

Deep eutectic solvents: Preparation, properties, and food applications

Deep Eutectic Solvents (DESs) emerge as innovative 21st-century solvents, supplanting traditional ones like ethanol and n-hexane. Renowned for their non-toxic, biodegradable, and water-miscible nature with reduced volatility, DESs are mostly synthesized through heating and stirring method. Physicochemical properties such as polarity, viscosity, density and surface tension of DESs influenced their application. This review paper gives the overview of application of eco-benign DESs in fruits, vegetables, cereals, pulses, spices, herbs, plantation crops, oil seed crops, medicinal and aromatic plants, seaweed, and milk for the extraction of bioactive compounds. Also, it gives insight of determination of pesticides, insecticides, hazardous and toxic compounds, removal of heavy metals, detection of illegal milk additive, purification of antibiotics and preparation of packaging film. Methodologies for separating bioactive compounds from DESs extracts are systematically examined. Further, safety regulations of DESs are briefly discussed and reviewed literature reveals prevalent utilization of DES-based bioactive compound rich extracts in cosmetics, indicating untapped potential of their application in the food industry.

Antibacterial and antifungal activities of natural deep eutectic solvents

The increasing antibiotic resistance towards a panel of microorganisms is one of the public health concerns. For this reason, the search for alternatives to the widely used antibiotic has been undertaken. In the era of sustainable chemistry, deep eutectic solvents (DESs) have emerged as promising antimicrobial agents. These solvents possess several advantages such as low volatility, low flammability, ease of preparation, and typically low cost of production. These properties make DES suitable for various applications, including extraction of biomolecules and preparation of cosmetics. Natural DESs (NADESs) are special category of DESs prepared from natural sources, which matched the recent trends of leaning back to nature, and decreasing dependence on synthetic precursors. NADES can be prepared by heating and stirring, freeze-drying, evaporation, grinding, and ultrasound-assisted and microwave-assisted synthesis. Utilizing NADESs as an alternative to traditional antibiotics, which become ineffective over time due to bacterial resistance, holds great promise for these reasons. This review aims to discuss the antimicrobial properties of multiple NADESs, including antibacterial and antifungal activities. To the best of our knowledge, this review is the first literature survey of the antimicrobial activities of NADESs. KEY POINTS: • Natural deep eutectic solvents are promising antimicrobial alternative to antibiotics • NADES holds high potential for their activity against bacterial resistance • NADES have also substantial antifungal activities.

A Sustainable Extraction Approach of Phytochemicals from Date (Phoenix dactylifera L.) Fruit Cultivars Using Ultrasound-Assisted Deep Eutectic Solvent: A Comprehensive Study on Bioactivity and Phenolic Variability

The present study aimed to evaluate the efficacy of natural deep eutectic solvents (NADESs) on the extraction of phytochemicals from eight Algerian date fruit cultivars (Phoenix dactylifera L.). In this study, lactic acid/sucrose-based NADESs were used as an alternative to conventional chemical solvents using the ultrasound-assisted extraction (UAE) method. The obtained extracts were assessed for the determination of bioactive compound contents, phenolic composition, antioxidant activity, and enzyme inhibitory potential. The results showed a considerable variation in phytochemical compositions and related activities between cultivars, where the greatest contents of total phenolics (1288.7 mg GAE/100 g), total flavonoids (53.8 mg QE/100 g), proanthocyanidins (179.5 mg CE/g), and total triterpenoids (12.88 mg OAE/100 g) were detected in the fruits of the Ourous cultivar. The same cultivar displayed the highest antioxidant capacity against DPPH• free radical (595 mg AAE/100 g), ABTS•+ cation radical (839 mg TE/100 g), and ferric reducing antioxidant potential (704 mg AAE/100 g). All extracts manifested moderate antioxidant activities tested by phosphomolybdenum, NO•, and linoleic acid lipid peroxidation assays. These extracts also exhibited interesting levels of in vitro enzyme inhibition; the Ourous cultivar gave the best inhibitory activity against α-amylase and acetylcholinesterase with 45 and 37%, respectively. HPLC-DAD-MS detected a total of five compounds, with phenolic acids and flavonoids being the main phenolics identified in the extract. The phenolic composition exhibited significant variability among cultivars. Notably, the highest amounts were revealed in the Tazizaout cultivar, with the predominance of gallic acid. The results confirmed that the combination of UAE and NADESs provides a novel and important alternative to chemical solvents for sustainable and environmentally friendly extraction and can represent a good alternative in food and pharmaceutical industry applications.

NaDES Application in Cosmetic and Pharmaceutical Fields: An Overview

Natural deep eutectic solvents (NaDES) represent a new generation of green, non-flammable solvents, useful as an efficient alternative to the well-known ionic liquids. They can be easily prepared and exhibit unexpected solubilizing power for lipophilic molecules, although those of a hydrophilic nature are mostly used. For their unique properties, they can be recommend for different cosmetic and pharmaceutical applications, ranging from sustainable extraction, obtaining ready-to-use ingredients, to the development of biocompatible drug delivery responsive systems. In the biomedical field, NaDES can be used as biopolymer modifiers, acting as delivery compounds also known as "therapeutic deep eutectic systems", being able to solubilize and stabilize different chemical and galenical formulations. The aim of this review is to give an overview of the current knowledge regarding natural deep eutectic solvents specifically applied in the cosmetic and pharmaceutical fields. The work could help to disclose new opportunities and challenges for their implementation not only as green alternative solvents but also as potential useful pathways to deliver bioactive ingredients in innovative formulations.

Nature of a Tetrabutylammonium Chloride-Levulinic Acid Deep Eutectic Solvent

A deep eutectic solvent was formed by considering the mixtures of tetrabutylammonium chloride and levulinic acid, and it is studied via a combined theoretical and experimental approach. Physicochemical properties were measured as a function of temperature, providing a macroscopic characterization of the fluid. Quantum chemistry and classical molecular dynamics simulations were carried out for the nanoscopic characterization, providing attention to the nature, extension, and dynamics of the hydrogen bonding network, which is at the root of the properties of the fluid. The reported study allows multiscale characterization of this fluid as an archetypical example of a natural, low-cost, and sustainable fluid.

From Nature to Innovation: The Uncharted Potential of Natural Deep Eutectic Solvents

This review discusses the significance of natural deep eutectic solvents (NaDESs) as a promising green extraction technology. It employs the consolidated meta-analytic approach theory methodology, using the Web of Science and Scopus databases to analyze 2091 articles as the basis of the review. This review explores NaDESs by examining their properties, challenges, and limitations. It underscores the broad applications of NaDESs, some of which remain unexplored, with a focus on their roles as solvents and preservatives. NaDESs' connections with nanocarriers and their use in the food, cosmetics, and pharmaceutical sectors are highlighted. This article suggests that biomimicry could inspire researchers to develop technologies that are less harmful to the human body by emulating natural processes. This approach challenges the notion that green science is inferior. This review presents numerous successful studies and applications of NaDESs, concluding that they represent a viable and promising avenue for research in the field of green chemistry.

Development and characterization of sustainable active pectin films: The role of choline chloride/glycerol-based natural deep eutectic solvent and lavender extracts

This study aimed to evaluate the potential effects of choline chloride: glycerol-based natural deep eutectic solvent (NADES) as a plasticizer, NADES extract (NADESext) of lavender as both plasticizer and active ingredient, as well as the lyophilized extract (LE) of lavender at different concentrations (0.5 %, 1 %, and 2 %) on the physical, mechanical, optical, thermal, barrier, morphological, and antioxidant properties of pectin films. The properties of the films were compared to those of the neat pectin film and the film plasticized with glycerol. The addition of plasticizers and LE increased thickness, water vapor permeability, and elongation at break values of the films while decreasing tensile strength and young modulus. Pectin films plasticized with glycerol, NADES, and NADESext had a similar color property but a lower opacity. The use of LE decreased lightness and increased opacity compared to the films with plasticizers. The addition of plasticizers revealed a smoother surface than neat pectin film while LE triggered the formation of agglomerates on the films. Changes in the FTIR spectra of the films showed some interactions between pectin and polyphenols in LE. The plasticizers had an insignificant effect on the antioxidant capacity of films whereas LE improved antioxidant capacity depending on the concentration. In conclusion, the results suggested that pectin films with NADES and LE could be beneficially used to improve antioxidant packaging technology along with acceptable mechanical properties.

A review on natural based deep eutectic solvents (NADESs): fundamentals and potential applications in removing heavy metals from soil

Natural based deep eutectic solvent (NADES) is a promising green solvent to replace the conventional soil washing solvent due to the environmental benign properties such as low toxicity, high biodegradability, high polarity or hydrophilicity, and low cost of fabrication process. The application of NADES is intensively studied in the extraction of organic compounds or natural products from vegetations or organic matters. Conversely, the use of the solvent in removing heavy metals from soil is severely lacking. This review focuses on the potential application of NADES as a soil washing agent to remove heavy metal contaminants. Hydrophilicity is an important feature of a NADES to be used as a soil washing solvent. In this context, choline chloride is often used as hydrogen bond acceptor (HBA) whereby choline chloride based NADESs showed excellent performance in the extraction of various solutes in the past studies. The nature of NADES along with its chemistry, preparation and designing methods as well as potential applications were comprehensively reviewed. Subsequently, related studies on choline chloride-based NADES in heavy metal polluted soil remediation were also reviewed. Potential applications in removing other soil contaminants as well as the limitations of NADES were discussed based on the current advancements of soil washing and future research directions were also proposed.

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.

Recovery of Polyphenols from Rosehip Seed Waste Using Natural Deep Eutectic Solvents and Ultrasonic Waves Simultaneously

Rosehips are processed and consumed in numerous forms, such as juice, wine, herbal tea, yogurt, preserved fruit, and canned products. The seeds share in fruit is 30-35% and they have recently been recognized as an important source of oil rich in unsaturated fatty acids. However, after defatting, seed waste may still contain some polar polyphenolic compounds, which have been scarcely investigated. The aim of this study was to examine the potential of the defatted seed waste as a source of polyphenols. For the defatting process, supercritical carbon dioxide extraction at 300 bar and 40 °C was applied. The capacity of eight different natural deep eutectic solvents (NADES) for the recovery of phenolics from defatted rosehip seed powder (dRSP) was examined. In the extracts obtained with ultrasound-assisted NADES extraction, twenty-one phenolic compounds were identified with LC-MS/MS, among which the most abundant were quinic acid (22.43 × 103 µg/g dRSP) and catechin (571.93 µg/g dRSP). Ternary NADES formulations based on lactic acid proved to be superior. Potential correlations between identified chemical compounds, solvent polarity and viscosity, as well as the compound distributions across studied solvent combinations in PCA hyperspace, were also investigated. PCA demonstrated that more polar NADES mixtures showed improved extraction potential. The established environmentally friendly process represents an approach of transforming rosehip seed waste into value-added products with the potential to be applied in the food industry and to contribute to sustainable production.

Natural Deep Eutectic Solvent based Ultrasound-assisted extraction: A green approach for extraction of sulfhydryl and mimosine from Leucaena leucocephala (Lam) de Wit seeds

Leucaena leucocephala (Lam.) de Wit seeds, also known as river tamarind, contain sulfhydryl compounds that exhibit antioxidant effects. However, these seeds also possess a toxic effect from mimosine. In this study, the river tamarind seeds were extracted using a natural deep eutectic solvent (NADES) based UAE. Among six NADES compositions screened, choline chloride-glycerol (ChCl-Gly) and choline chloride-sucrose (ChCl-Suc) were selected to be further optimized using a Box-Behnken Design in the RSM. The optimization of total sulfhydryl content was performed in 17 runs using three variables, namely water content in NADES (39%, 41%, and 43%), extraction time (5, 10, and 15 min), and the liquid-solid ratio (3, 5, and 7 mL/g). The highest concentration of sulfhydryls was obtained from ChCl-Gly-UAE (0.89 mg/g sample) under the conditions of a water content in NADES of 41% (v/v) and a liquid-solid ratio of 3 mL/g for 15 min, followed by that of from ChCl-Suc-UAE extract under the conditions of water content in NADES of 43% (v/v) and the liquid-solid ratio of 3 mL/g for 10 min with total sulfhydryl level was 0.67 mg/g sample. The maceration method using 30% ethanol resulted in the lowest level of sulfhydryls with a value of 0.52 mg/g. The mimosine compounds obtained in the NADES-based UAE (ChCl-Suc and ChCl-Gly) extracts were 4.95 and 7.67 mg/g, respectively, while 12.56 mg/g in the 30% ethanol-maceration extract. The surface morphology of L. leucocephala seed before and after extraction was analyzed using scanning electron microscopy. Therefore, it can be concluded that the use of ChCl-Suc and ChCl-Gly in NADES-based UAE is more selective in attracting sulfhydryl compounds than that of 30% ethanol-maceration extraction.

Green Extraction of Polyphenols via Deep Eutectic Solvents and Assisted Technologies from Agri-Food By-Products

Polyphenols are the largest group of phytochemicals with important biological properties. Their presence in conveniently available low-cost sources, such as agri-food by-products, has gained considerable attention in their recovery and further exploitation. Retrieving polyphenols in a green and sustainable way is crucial. Recently, deep eutectic solvents (DESs) have been identified as a safe and environmentally benign medium capable of extracting polyphenols efficiently. This review encompasses the current knowledge and applications of DESs and assisted technologies to extract polyphenols from agri-food by-products. Particular attention has been paid to fundamental mechanisms and potential applications in the food, cosmetic, and pharmaceutical industries. In this way, DESs and DESs-assisted with advanced techniques offer promising opportunities to recover polyphenols from agri-food by-products efficiently, contributing to a circular and sustainable economy.

Exploring carbohydrate extraction from biomass using deep eutectic solvents: Factors and mechanisms

Deep eutectic solvents (DESs) are increasingly being recognized as sustainable and promising solvents because of their unique properties: low melting point, low cost, and biocompatibility. Some DESs possess high viscosity, remarkable stability, and minimal toxicity, enhancing their appeal for diverse applications. Notably, they hold promise in biomass pretreatment, a crucial step in biomass conversion, although their potential in algal biomass carbohydrates extraction remains largely unexplored. Understanding the correlation between DESs' properties and their behavior in carbohydrate extraction, alongside cellulose degradation mechanisms, remains a gap. This review provides an overview of the use of DESs in extracting carbohydrates from lignocellulosic and algal biomass, explores the factors that influence the behavior of DESs in carbohydrate extraction, and sheds light on the mechanism of cellulose degradation by DESs. Additionally, the review discusses potential future developments and applications of DESs, particularly extracting carbohydrates from algal biomass.

The Antioxidant and Prebiotic Activities of Mixtures Honey/Biomimetic NaDES and Polyphenols Show Differences between Honeysuckle and Raspberry Extracts

In our previous research, we demonstrated that honey and its biomimetic natural deep eutectic solvent (NaDES) modulate the antioxidant activity (AOA) of the raspberry extract (RE). In this study, we evaluated the AOA behaviour of the mixture honey/NaDES-honeysuckle (Lonicera caprifolium, LFL) extract and compared it with the mixture honey/NaDES-RE. These two extracts have similar major flavonoids and hydroxycinnamic acid compounds but differ in their total content and the presence of anthocyanins in RE. Therefore, it was of interest to see if the modulation of the LFL polyphenols by honey/NaDES was similar to that of RE. We also evaluated the prebiotic activity of these mixtures and individual components on Limosilactobacillus reuteri DSM 20016. Although honey/NaDES modulated the AOA of both extracts, from synergism to antagonism, the modulation was different between the two extracts for some AOA activities. Honey/NaDES mixtures enriched with LFL and RE did not show significant differences in bacterial growth stimulation. However, at a concentration of 45 mg/mL, the honey -LFL mixture exhibited a higher effect compared to the honey-RE mixture. The antioxidant and prebiotic properties of mixtures between honey and polyphenol-rich extracts are determined by multiple interactions in complex chemical systems.

Rutin: Family Farming Products' Extraction Sources, Industrial Applications and Current Trends in Biological Activity Protection

In vitro and in vivo studies have demonstrated the bioactivity of rutin, a dietary flavonol naturally found in several plant species. Despite widespread knowledge of its numerous health benefits, such as anti-inflammatory, antidiabetic, hepatoprotective and cardiovascular effects, industrial use of rutin is still limited due to its low solubility in aqueous media, the characteristic bitter and astringent taste of phenolic compounds and its susceptibility to degradation during processing. To expand its applications and preserve its biological activity, novel encapsulation systems have been developed. This review presents updated research on the extraction sources and methodologies of rutin from fruit and vegetable products commonly found in a regular diet and grown using family farming approaches. Additionally, this review covers quantitative analysis techniques, encapsulation methods utilizing nanoparticles, colloidal and heterodisperse systems, as well as industrial applications of rutin.

Epsom Salt-Based Natural Deep Eutectic Solvent as a Drilling Fluid Additive: A Game-Changer for Shale Swelling Inhibition

Shale rock swelling poses a significant challenge during drilling a well, leading to issues related to wellbore instability. Water-based mud with specific shale inhibitors is preferred over oil-based drilling mud due to its lower environmental impact. Recently, ionic liquids (ILs) have emerged as potential shale inhibitors due to their adjustable properties and strong electrostatic attraction. However, research has shown that the most commonly used class of ILs (imidazolium) in drilling mud are toxic, non-biodegradable, and expensive. Deep Eutectic Solvents (DESs), the fourth generation of ionic liquids, have been proposed as a cheaper and non-toxic alternative to ILs. However, ammonium salt-based DESs are not truly environmentally friendly. This research explores the utilization of Natural Deep Eutectic Solvent (NADES) based on Epsom salt (a naturally occurring salt) and glycerine as a drilling fluid additive. The drilling mud is prepared according to API 13B-1 standards. Various concentrations of NADES-based mud are tested for yield point, plastic viscosity, and filtration properties for both aged and non-aged samples. The linear swell meter is used to determine the percentage swelling of the NADES-based mud, and the results are compared with the swelling caused by KCl- and EMIM-Cl-based mud. FTIR analysis is conducted to understand the interaction between NADES and clay, while surface tension, d-spacing (XRD), and zeta potential are measured to comprehend the mechanism of swelling inhibition by NADES. The findings reveal that NADES improves the yield point and plastic viscosity of the mud, resulting in a 26% reduction in mudcake thickness and a 30.1% decrease in filtrate volume at a concentration of 1%. NADES achieves a significant 49.14% inhibition of swelling at the optimal concentration of 1%, attributed to its ability to modify surface activity, zeta potential of clay surfaces, and d-spacing of clay layers. Consequently, NADES emerges as a non-toxic, cost-effective, and efficient shale inhibitor that can replace ILs and DESs.

Innovative Strategy for Aroma Stabilization Using Green Solvents: Supercritical CO2 Extracts of Satureja montana Dispersed in Deep Eutectic Solvents

The aim of this work was to establish the potential of natural deep eutectic solvents (NADES) for the stabilization of aroma volatile organic compounds from a natural source. Satureja montana was used as a source of volatile components, as it is rich in terpenes of great commercial and biological importance, such as carvacrol, thymol, and thymoquinone, among others. Supercritical CO₂ was used to extract the lipophilic fraction of S. montana, which was further directly dispersed in NADES. The stabilizing capacity of seven different NADES based on betaine and glycerol was analyzed. The stability of the components in NADES was monitored by analyzing the headspace profile during 6 months of storage at room temperature. The changes in the headspace profile over time were analyzed by using different statistical and chemometric tools and the Wilcoxon matched pair test. It was determined that alterations over time occurred such as degradation and oxidation, and they were the most prominent in the control. In addition, the indicator of decreased stability of the control was the formation of the new compounds that could compromise the quality of the product. In the stabilized NADES samples, the changes were significantly less prominent, indicating that the NADES had a stabilizing effect on the volatile compounds. According to Wilcoxon matched pair test, the most efficient stability was achieved by using betaine/ethylene glycol, glycerol/glucose, and betaine/sorbitol/water. Therefore, by applying two green solvents, a sustainable approach for obtaining pure and high-quality S. montana extracts with extended stability at room temperature was established.

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.

Contemporary methods for the extraction and isolation of natural products

Extraction is a vital step in obtaining pure bioactive natural compounds for medical, scientific and commercial use. Recently, interest in extracting natural products for applications across the food, pharmaceutical, and cosmetic industries has grown rapidly, driving demand for newer, more efficient extraction methods. To develop our understanding of this field, BMC Chemistry has launched a new article Collection titled "Contemporary methods for the extraction and isolation of natural products".

NaDES as a green technological approach for the solubility improvement of BCS class II APIs: An insight into the molecular interactions

Recently, Natural Deep Eutectic Solvents (NaDES) have emerged as potential solvents for boosting drug bioavailability. In this work, the mechanism of solubility enhancement of some APIs belonging to BCS class II (tolbutamide, nimesulide, domperidone and cinnarizine) in these eutectic bio-solvents was investigated in order to get deeper insights into the molecular interactions between the NaDES components and the selected drugs. Different NaDES formulations based on choline chloride, proline, solid organic acids (citric, tartaric and malic acid), sugars (glucose and xylitol) and water were prepared by mild heating (70 °C). Characterization of unloaded NaDES (pH, Karl Fisher titration, viscosity and FTIR analysis) indicated that the type of Hydrogen Bond Acceptor (HBA) and Hydrogen Bond Donor (HBD), their molar ratio as well as water amount strongly affect the extent of H-bonding interactions. Hard gelatin capsules filled with NaDES maintained their integrity until 6 months, proving that all water molecules participate in H-bond network. APIs' solubility enhancement was significant in all NaDES with respect to buffer solutions (pH 1.2 and 6.8). Analysing NaDES having Choline as HBA, it was found that the solubility of smaller molecules increased using larger HBD, while higher molecular weight APIs can be better inserted into the network formed by smaller HBD. NOE experiments demonstrated the formation of a robust supramolecular structure among the protons of choline, those of organic acid and water. In addition, 1D ROESY spectra revealed for the first time the crucial role of choline (methyl groups) in establishing hydrophobic interactions with the relative aliphatic or aromatic portion of the drugs. These data suggest the complex structure of the API-NaDES supramolecular assembly and underline that drug solubility is dependent on a balance network of H-bonds and hydrophobic interactions as well. Understanding the type of interactions between the API and NaDES is essential for their use as effective solubilisation aid.

Green and sustainable extraction of lignin by deep eutectic solvent, its antioxidant activity, and applications in the food industry

Lignin, an amorphous biomacromolecule abundantly distributed in the plant kingdom, has gained considerable attention due to its intrinsic bioactivities and renewable nature. Owing to its polyphenolic structure, lignin has a variety of human health activities, including antioxidant, antimicrobial, antidiabetic, antitumor, and other activities. The extraction of lignin from various sources in a green and sustainable manner is critical in the food industry. Deep eutectic solvent (DES) has recently been recognized as a class of safe and environmentally friendly media capable of efficiently extracting lignin. This article comprehensively reviews the recent advances in lignin extraction using DES, discusses the influential factors on the antioxidant activity of lignin, interprets the relationship between antioxidant activity and lignin structure, and overviews the applications of lignin in the food industry. We aim to highlight the advantages of DES in lignin extraction and valorization from the nutrition and food views.

The Ability of Acid-Based Natural Deep Eutectic Solvents to Co-Extract Elements from the Roots of Glycyrrhiza glabra L. and Associated Health Risks

The roots of licorice (Glycyrrhiza glabra L.) have been widely used in traditional and officinal medicines for the treatment of different diseases. Natural deep eutectic solvents (NADES) have become popular for the extraction of active principles from medicinal plants. However, the ability of NADES to co-extract trace elements during the isolation of target active compounds is rarely investigated. The aim of this study was to analyze the content of trace elements in acid-based NADES extracts from the roots of G. glabra and the health risks associated with them. In this study, we have tested for the first time the ability of several acid-based NADES to co-extract glycyrrhizic acid (GA) and trace elements from the roots of G. glabra. GA has been identified as the dominant phytochemical in G. glabra NADES extracts (0.145-0.495 mg/g). Due to the close pKa of lactic acid and GA, the yield of GA in lactic acid-based NADES was higher in comparison with other tested NADES. The yield of GA in NADES3-NADES5 was statistically significant and surpassed the yield of GA in water. The recovery of all elements (except Li) by all tested NADES was low (less than 6%). According to an ANOVA test, the hydrogen bond donor type plays a decisive role in the extraction of elements. A strong positive correlation between the recovery of GA and MPI was noted. The metal pollution index, hazard quotient, hazard index, and chronic daily intake were calculated and suggest that all tested NADES extracts of G. glabra roots were nontoxic and possess no health risk for both ingestion and topical application.

Research Progress on the Preparation and Action Mechanism of Natural Deep Eutectic Solvents and Their Application in Food

Natural deep eutectic solvent (NADES) is the eutectic mixture which is formed by hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs) with a certain molar ratio through hydrogen bonding. NADES is a liquid with low cost, easy preparation, biodegradability, sustainability and environmental friendliness at room temperature. At present, it is widely used in food, medicine and other areas. First, the composition, preparation and properties of NADES are outlined. Second, the potential mechanism of NADES in freezing preservation, the removal of heavy metals from food and the extraction of phenolic compounds, and its application in cryopreservation, food analysis and food component extraction, and as a food taste enhancer and food film, are summarized. Lastly, the potential and challenges of its application in the food field are reviewed. This review could provide a theoretical basis for the wide application of NADES in food processing and production.

Pressurized natural deep eutectic solvents: An alternative approach to agro-soy by-products

Soybeans are mainly used for food and biodiesel production. It is estimated that soy crops worldwide will leave about 651 million metric tons of branches, leaves, pods, and roots on the ground post-harvesting in 2022/23. These by-products might serve as largely available and cheap source of high added-value metabolites, such as flavonoids, isoflavonoids, and other phenolic compounds. This work aimed to explore green approaches based on the use of pressurized and gas expanded-liquid extraction combined with natural deep eutectic solvents (NADESs) to achieve phenolic-rich extracts from soy by-products. The total phenolic and flavonoid contents of the generated extracts were quantified and compared with conventional solvents and techniques. Pressurized liquid extraction (PLE) with choline chloride/citric acid/water (1:1:11 – molar ratio) at 120°C, 100 bar, and 20 min, resulted in an optimized condition to generate phenolic and flavonoid-rich fractions of soy by-products. The individual parts of soy were extracted under these conditions, with their metabolic profile obtained by UHPLC-ESI-QToF-MS/MS and potential antioxidant properties by ROS scavenging capacity. Extracts of soy roots presented the highest antioxidant capacity (207.48 ± 40.23 mg AA/g), three times higher than soybean extracts (68.96 ± 12.30). Furthermore, Hansen solubility parameters (HSPs) were applied to select natural hydrophobic deep eutectic solvents (NaHDES) as substituents for n-heptane to defat soybeans. Extractions applying NaHDES candidates achieved a similar yield and chromatography profile (GC-QToF-MS) to n-heptane extracts.

Extraction of Lycopene from Tomato Using Hydrophobic Natural Deep Eutectic Solvents Based on Terpenes and Fatty Acids

The present study proposes a green extraction approach for the recovery of lycopene from tomato fruits. Different hydrophobic natural deep eutectic solvents (HNADESs) based on terpenes (i.e., menthol and thymol) and fatty acids (i.e., decanoic acid and dodecanoic acid) were prepared at different molar ratios, characterised in terms of density, rheological properties, and Fourier transform-infrared (FT-IR) spectroscopy, and were examined for their effectiveness to extract lycopene from tomato. Response surface methodology (RSM) was employed to optimise the extraction parameters, namely duration (min) and solvent:solid ratio (v/w). Spectrophotometry and RP-HPLC-DAD were used in order to monitor the process efficiency. The combination of decanoic acid and dodecanoic acid was found to exhibit comparable extraction capacity to acetone. Taking into account that the HNADESs used in the present study are considered green, biodegradable and of low cost, the obtained carotenoid rich extracts are expected to be of use in industrial food applications.

Microwave-assisted extraction of antioxidant compounds from by-products of Turkish hazelnut (Corylus avellana L.) using natural deep eutectic solvents: Modeling, optimization and phenolic characterization

An environmentally friendly method using natural deep eutectic solvents (NADES) and microwave-assisted extraction (MAE) for the recovery of bioactive compounds from hazelnut pomace (a hazelnut oil process by-product) was developed to contribute to their sustainable valorization. Eight different NADES were prepared for the extraction of antioxidant constituents from hazelnut pomace, and choline chloride:1,2-propylene glycol (CC-PG) was determined as the most suitable NADES, considering their extraction efficiency and physicochemical properties. After selecting suitable NADES, operational parameters for the MAE process of antioxidants from hazelnut pomace were optimized and modeled using response surface methodology. For the highest recovery of antioxidants, the operational parameters of the MAE process were found to be 24% water, 38 min, 92 °C and 18 mL/0.1 g-DS. Under optimized conditions, extracts of both pomace as a by-product and unprocessed hazelnut flours of three different hazelnut samples (Tombul, Çakıldak, and Palaz) were prepared, and their antioxidant capacities were evaluated by spectrophotometric methods. Antioxidant capacities of CC-PG extracts of all hazelnut samples were 2-3 times higher than those of ethanolic extracts. In addition, phenolic characterization of the prepared extracts was carried out using the UPLC-PDA-ESI-MS/MS system. The results of this study suggest that hazelnut by-products can potentially be considered an important and readily available source of natural antioxidants. Furthermore, the modeled MAE procedure has the potential to create an effective and sustainable alternative for pharmaceutical and food industries.

Comparison of Vibrational Spectroscopic Techniques for Quantification of Water in Natural Deep Eutectic Solvents

Vibrational spectroscopic techniques, i.e., attenuated total reflectance infrared (ATR-IR), near infrared spectroscopy (NIRS) and Raman spectroscopy (RS), coupled with Partial Least Squares Regression (PLSR), were evaluated as cost-effective label-free and reagent-free tools to monitor water content in Levulinic Acid/L-Proline (LALP) (2:1, mol/mol) Natural Deep Eutectic Solvent (NADES). ATR-IR delivered the best outcome of Root Mean Squared Error (RMSE) of Cross-Validation (CV) = 0.27% added water concentration, RMSE of Prediction (P) = 0.27% added water concentration and mean % relative error = 2.59%. Two NIRS instruments (benchtop and handheld) were also compared during the study, respectively yielding RMSECV = 0.35% added water concentration, RMSEP = 0.56% added water concentration and mean % relative error = 5.13% added water concentration, and RMECV = 0.36% added water concentration, RMSEP = 0.68% added water concentration and mean % relative error = 6.23%. RS analysis performed in quartz cuvettes enabled accurate water quantification with RMECV = 0.43% added water concentration, RMSEP = 0.67% added water concentration and mean % relative error = 6.75%. While the vibrational spectroscopic techniques studied have shown high performance in relation to reliable determination of water concentration, their accuracy is most likely related to their sensitivity to detect the LALP compounds in the NADES. For instance, whereas ATR-IR spectra display strong features from water, Levulinic Acid and L-Proline that contribute to the PLSR predictive models constructed, NIRS and RS spectra are respectively dominated by either water or LALP compounds, representing partial molecular information and moderate accuracy compared to ATR-IR. However, while ATR-IR instruments are common in chemistry and physics laboratories, making the technique readily transferable to water quantification in NADES, Raman spectroscopy offers promising potential for future development for in situ, sample withdrawal-free analysis for high throughput and online monitoring.

Structure, Organization, and Heterogeneity of Water-Containing Deep Eutectic Solvents

The spectroscopy and structural dynamics of a deep eutectic mixture (KSCN/acetamide) with varying water content is investigated from 2D IR (with the C-N stretch vibration of the SCN^- anions as the reporter) and THz spectroscopy. Molecular dynamics simulations correctly describe the nontrivial dependence of both spectroscopic signatures depending on water content. For the 2D IR spectra, the MD simulations relate the steep increase in the cross-relaxation rate at high water content to the parallel alignment of packed SCN^- anions. Conversely, the nonlinear increase of the THz absorption with increasing water content is mainly attributed to the formation of larger water clusters. The results demonstrate that a combination of structure-sensitive spectroscopies and molecular dynamics simulations provides molecular-level insights into the emergence of heterogeneity of such mixtures by modulating their composition.

Food Industry Byproducts as Starting Material for Innovative, Green Feed Formulation: A Sustainable Alternative for Poultry Feeding

Rising global populations and enhanced standards of living in so-called developing countries have led to an increased demand of food, in particular meat, worldwide. While increasing the production of broiler meat could be a potential solution to this problem, broiler meat is plagued by health concerns, such as the development of antimicrobial resistance and lower meat quality. For this reason, the supplementation of poultry feed with vitamins and antioxidant compounds, such as polyphenols, has become an attractive prospect for research in this sector. Such supplements could be obtained by extraction of agricultural byproducts (in particular, grape pomaces and artichoke leaves and bracts), thus contributing to reductions in the total amount of waste biomass produced by the agricultural industry. In this review, the effects of poultry feed supplementation with bioactive extracts from grape pomace (skins and/or seeds), as well as extracts from artichoke leaves and bracts, were explored. Moreover, the various methods that have been employed to obtain extracts from these and other agricultural byproducts were listed and described, with a particular focus on novel, eco-friendly extraction methods (using, for example, innovative and biocompatible solvents like Deep Eutectic Solvents (DESs)) that could reduce the costs and energy consumption of these procedures, with similar or higher yields compared to standard methods.

Utilization of Nanotechnology to Improve the Application and Bioavailability of Phytochemicals Derived from Waste Streams

Phytochemicals are relatively small molecular species found in edible plants that may exhibit a diverse range of techno- and biofunctional attributes. In particular, there has been great interest in the identification, isolation, and utilization of dietary phytochemicals that can be used as natural pigments, antioxidants, or antimicrobials or that may improve human health and wellbeing by preventing chronic diseases, such as cardiovascular diseases, diabetes, obesity, and cancer. Relatively high levels of these phytochemicals are often present in the waste streams produced by the food and agriculture industry, such as the peels, stems, roots, or leaves of plants, that are normally discarded or turned into animal foods. From an economic and environmental perspective, it would be advantageous to convert these waste streams into value-added functional ingredients, which is consistent with the creation of a more circular economy. Bioactive phytochemicals can be isolated from agricultural and food waste streams using green extraction methods and then incorporated into plant-based functional foods or biodegradable active packaging materials. The utilization of phytochemicals in the food industry is often challenging. They may chemically degrade in the presence of light, heat, oxygen, and some pH conditions, thereby altering their biological activity. They may have low solubility in aqueous solutions and gastrointestinal fluids, thereby making them difficult to introduce into foods and leading to a low bioavailability. These challenges can sometimes be overcome using nanoencapsulation, which involves trapping the phytochemicals inside tiny food-grade particles. These nanoparticles may be assembled from edible lipids, proteins, carbohydrates, and/or surfactants and include nanoemulsions, solid lipid nanoparticles, nanoliposomes, and biopolymer nanoparticles. In this manuscript, we review a number of important phytochemicals and nanoencapsulation methods used to improve their efficacy.

A density functional theory based tight-binding study on the water effect on nanostructuring of choline chloride + ethylene glycol deep eutectic solvent

The effect of water on the properties of an archetypical type III deep eutectic solvent [choline chloride : ethyleneglycol (1:2)] is analyzed using ab initio molecular dynamics simulations in the 0 to 60 wt. % water content range. The properties of the mixed fluids are studied considering nanostructuring, intermolecular forces (hydrogen bonding), the energy of interactions, dynamic properties, and domain analysis. The reported results confirm that the change in the properties of the studied deep eutectic solvent is largely dependent on the amount of water. The competing effect of water molecules for the available hydrogen bonding sites determines the evolution of the properties upon water sorption. The main structural features of the considered deep eutectic were maintained even for large water contents; thus, its hydrophilicity could be used for tuning fluid physicochemical properties.

Monitoring the water content in NADES extracts from spirulina biomass by means of ATR-IR spectroscopy

Attenuated total reflectance-infrared spectroscopy (ATR-IR) coupled with partial least squares regression (PLSR) was evaluated as a rapid, label free and cost-effective tool to quantify water content in extracts obtained from spirulina wet biomass using a glucose glycerol natural deep eutectic solvent (NADES). NADESs are green, renewable and biodegradable solvents with unique properties outcompeting existing organic solvents, for instance, for plant or biomass extraction. The properties of NADESs depend critically on their water concentration, and therefore, it is essential to develop methods to monitor it, to ensure optimal extraction efficiency and experimental repeatability to achieve a better standardization of extraction protocols. First, Karl Fischer titration was performed on a set of 20 NADES extracts in order to obtain reference water concentrations. Secondly, ATR-IR spectra were collected and subjected to datamining to construct PLSR predictive models. An R² value of 0.9996, a mean root mean square error of cross validation of 0.136% w/w and a root mean square error of prediction of 0.130% w/w highlight the feasibility and reliability to perform quantitative analysis using ATR-IR. Moreover, the mean relative error percentage achieved, ∼0.5%, confirms the high accuracy of water concentration determination in NADES extracts. This work demonstrates that powerful alternatives are available to provide more environmentally responsible analytical protocols. ATR-IR spectroscopy applied to NADES extracts does not require any sample preparation, reagents or solvents and has minimal requirements for single use consumables. The technique is consistent with current concerns to develop greener chemistry, especially in the field of extraction of natural compounds from plants which currently represents a major focus of interest in both research and industry.

The Impact of Natural Deep Eutectic Solvents and Extraction Method on the Co-Extraction of Trace Metals from Fucus vesiculosus

In recent years, natural deep eutectic solvents (NADES) have been widely investigated for the extraction of food and medicinal plants as well as seaweeds. However, the ability of NADES for trace elements co-extraction from natural sources is not well investigated. The aim of this study was to investigate the ability of common NADES for trace elements co-extraction from Fucus vesiculosus. All of the tested NADES did not recover As and Co (concentration Collapse

Key Words

• Fucus vesiculosus
• NADES
• extraction
• hazard quotient
• health risk
• natural deep eutectic solvents
• trace elements
• trace metals

Collapse

MESH Headings

• Deep Eutectic Solvents
• Fucus
• Plant Extracts
• Solvents
• Water

Collapse

Grants

• 121091600104-7 Ministry of Science and Higher Education of the Russian Federation within the framework of the Government Assignment to the Murmansk Marine Biological Institute Russian Academy of Sciences
• 075-15-2021-685; dated 26 July 2021 on the provision of the federal budget grants Ministry of Science and Higher Education of the Russian Federation

Collapse

Affiliation(s)

Alexander N. Shikov Murmansk Marine Biological Institute of the Russian Academy of Sciences (MMBI RAS), Vladimirskaya, 17, 183010 Murmansk, Russia; (E.D.O.); (O.N.P.) Department of Pharmaceutical Formulations, St. Petersburg State Chemical Pharmaceutical University, Prof. Popov, 14, 197376 Saint-Petersburg, Russia;
Ekaterina D. Obluchinskaya Murmansk Marine Biological Institute of the Russian Academy of Sciences (MMBI RAS), Vladimirskaya, 17, 183010 Murmansk, Russia; (E.D.O.); (O.N.P.)
Elena V. Flisyuk Department of Pharmaceutical Formulations, St. Petersburg State Chemical Pharmaceutical University, Prof. Popov, 14, 197376 Saint-Petersburg, Russia;
Inna I. Terninko Core Shared Research Facilities “Analytical Center”, St. Petersburg State Chemical Pharmaceutical University, Prof. Popov, 14, 197376 Saint-Petersburg, Russia; (I.I.T.); (Y.E.G.)
Yulia E. Generalova Core Shared Research Facilities “Analytical Center”, St. Petersburg State Chemical Pharmaceutical University, Prof. Popov, 14, 197376 Saint-Petersburg, Russia; (I.I.T.); (Y.E.G.)
Olga N. Pozharitskaya Murmansk Marine Biological Institute of the Russian Academy of Sciences (MMBI RAS), Vladimirskaya, 17, 183010 Murmansk, Russia; (E.D.O.); (O.N.P.)

Collapse

Enhanced Extraction Efficiency of Flavonoids from Pyrus ussuriensis Leaves with Deep Eutectic Solvents

In this study, deep eutectic solvents (DESs) were synthesized using different ratios of choline chloride (CC) and dicarboxylic acids, and their eutectic temperatures were determined. The DES synthesized using CC and glutaric acid (GA), which showed a higher extraction efficiency than conventional solvents, was used for the extraction of flavonoid components from Pyrus ussuriensis leaves (PUL), and the extraction efficiency was evaluated using the response surface methodology. The flavonoid components rutin, hyperoside, and isoquercitrin were identified through high-performance liquid chromatography (HPLC), equipped with a Waters 2996 PDA detector, and HPLC mass spectrometry (LC-MS/MS) analyses. The optimum extraction was achieved at a temperature of 30 °C using DES in a concentration of 30.85 wt.% at a stirring speed of 1113 rpm and an extraction time of 1 h. The corresponding flavonoid content was 217.56 μg/mL. The results were verified by performing three reproducibility experiments, and a high significance, with a confidence range of 95%, was achieved. In addition, the PUL extracts exhibited appreciable antioxidant activity. The results showed that the extraction process using the DES based on CC and GA in a 1:1 molar ratio could effectively improve the yield of flavonoids from PUL.

Oriented Deep Eutectic Solvents as Efficient Approach for Selective Extraction of Bioactive Saponins from Husks of Xanthoceras sorbifolia Bunge

The husks of Xanthoceras sorbifolia Bunge (X. sorbifolia), as by-products of industrial production, have brought a severe burden to the environment and caused an enormous waste of resources. Bioactive triterpenoid saponins are rich in the husks. To reuse the husks and gain high-quality saponin products, saponin-oriented deep eutectic solvents (DESs), as an efficient and selective extraction strategy from X. sorbifolia husks, were designed for the first time. The enhancement of the extraction rate was investigated by screening solvents from acidic DESs and response surface methodology (RSM) optimization. As a result, the tetrapropylammonium bromide-lactic acid (TPMBr-La) was the most efficient DESs, with an extraction efficiency of up to 135% higher than 70% ethanol. A maximum extraction rate of 72.11 ± 0.61 mg Re/g dw was obtained under the optimized parameters. Scanning electron microscope graphs revealed that damage to the microstructure caused by DESs enhanced the extraction efficiency. Moreover, the recovery of total saponins with D101 macroporous resin was consistent with the pseudo-second-order kinetic model. Seven saponins were also identified by HPLC-MS analysis. Finally, TPMBr-La extracts exhibited 92.30 ± 1.10% DPPH radical scavenging rate at 100 μg/mL, and 92.20 ± 0.30% ABTS radical scavenging rate at 1200 μg/mL. Our current research proposes a selective and high-efficiency substitute for the extraction of saponins and might contribute to further DESs application in the recycling of by-products.