Tailoring and recycling of deep eutectic solvents as sustainable and efficient extraction media

Phosphonium chloride-based deep eutectic solvents inhibit pathogenic Acanthamoeba castellanii belonging to the T4 genotype

Herein, we investigated the anti-amoebic activity of phosphonium-chloride-based deep eutectic solvents against pathogenic Acanthamoeba castellanii of the T4 genotype. Deep eutectic solvents are ionic fluids composed of two or three substances, capable of self-association to form a eutectic mixture with a melting point lower than each substance. In this study, three distinct hydrophobic deep eutectic solvents were formulated, employing trihexyltetradecylphosphonium chloride as the hydrogen bond acceptor and aspirin, dodecanoic acid, and 4-tert-butylbenzoic acid as the hydrogen bond donors. Subsequently, all three deep eutectic solvents, denoted as DES1, DES2, DES3 formulations, underwent investigations comprising amoebicidal, adhesion, excystation, cytotoxicity, and cytopathogenicity assays. The findings revealed that DES2 was the most potent anti-amoebic agent, with a 94% elimination rate against the amoebae within 24 h at 30 °C. Adhesion assays revealed that deep eutectic solvents hindered amoebae adhesion to human brain endothelial cells, with DES2 exhibiting 88% reduction of adhesion. Notably, DES3 exhibited remarkable anti-excystation properties, preventing 94% of cysts from reverting to trophozoites. In cytopathogenicity experiments, deep eutectic solvent formulations and dodecanoic acid alone reduced amoebae-induced human brain endothelial cell death, with DES2 showing the highest effects. Lactate dehydrogenase assays revealed the minimal cytotoxicity of the tested deep eutectic solvents, with the exception of trihexyltetradecylphosphonium chloride, which exhibited 35% endothelial cell damage. These findings underscore the potential of specific deep eutectic solvents in combating pathogenic Acanthamoeba, presenting promising avenues for further research and development against free-living amoebae.

Chemical profiling of botanical extracts obtained in NADES systems using centrifugal partition chromatography combined with 13 C NMR dereplication-Hypericum perforatum as a case study

INTRODUCTION

Natural deep eutectic solvents (NADES) have emerged as interesting extractants to develop botanical ingredients. They are nontoxic and biodegradable, nonflammable, easy to prepare, and able to solubilize a wide range of molecules. However, NADES extracts remain difficult to analyze because the metabolites of interest stay highly diluted in the nonvolatile viscous NADES matrix.

OBJECTIVE

This study presents a robust analytical workflow for the chemical profiling of NADES extracts. It is applied to Hypericum perforatum aerial parts extracted with the neutral mixture fructose/glycerol/water (3/1/1, w/w/w), and compared to the chemical profiling of a classical dry methanol extract.

METHODS

Exploiting polarity differences between metabolites, the H. perforatum NADES extract was partitioned in a liquid-liquid solvent system to trap the hydrophilic NADES constituents in the lower phase. The upper phase, containing a diversity of secondary metabolites from H. perforatum, was fractionated by centrifugal partition chromatography. All fractions were chemically investigated using a 13 C NMR dereplication method which involves hierarchical clustering analysis of the whole NMR dataset, a natural metabolite database for metabolite identification, and 2D NMR analyses for validation. Liquid chromatography-mass spectrometry (LC-MS) analyses were also performed to complete the identification process.

RESULTS

A range of 21 metabolites were unambiguously identified, including glycosylated flavonols, lactones, catechins, phenolic acids, lipids, and simple sugars, and 15 additional minor extract constituents were annotated by LC-MS based on exact mass measurements.

CONCLUSION

The proposed identification process is rapid and nondestructive and provides good prospects to deeply characterize botanical extracts obtained in nonvolatile and viscous NADES systems.

Recycling of deep eutectic solvent in the extraction of ferulic acid from oil palm empty fruit bunch

The study explored ferulic acid extraction from palm empty fruit bunch (EFB) fiber using deep eutectic solvent (DES) of chlorine chloride-acetic acid as the extraction medium and the way to recover and recycle the DES thereafter. Antisolvent was added to selectively precipitate the ferulic acid, which was recovered by filtration thereafter. Recycling the DES without further purification led to increased ferulic acid yield with each subsequent extraction, likely due to retained ferulic acid. The retained ferulic acid and other impurities could be removed by precipitation brought upon by the addition of a second antisolvent. 1H nuclear magnetic resonance revealed that there was no excess ferulic acid in the recycled DES-treated with two types of antisolvents (ethanol and water). The yield of ferulic acid increased from 0.1367-0.1856 g/g when treated with only one antisolvent to 0.1368-0.2897 g/g with two antisolvent treatments. Oil droplets were also observed in the DES upon the addition of antisolvent 2, with recovered oil ranging from 0.6% to 3%. The study emphasized the significance of using DES as an extraction medium for ferulic acid from oil palm EFB fiber and the method to recycle the DES for subsequent processes.

The Utilization of an Aloe Vera Rind By-Product: Deep Eutectic Solvents as Eco-Friendly and Recyclable Extraction Media of Polyphenolic Compounds

In this study, an optimized environmentally friendly procedure was employed to enhance the sustainable utilization of phenolic antioxidants derived from aloe vera rind by-products. The procedure involved the application of ultrasound-assisted extraction (UAE) in combination with deep eutectic solvents (DESs). Eleven different DESs and three conventional solvents were employed as extraction media for polyphenolic compounds. Choline chloride-citric acid (ChCl-CA) was selected as the most suitable extractant, considering its extraction efficiency in relation to the total phenolic content. The operating conditions of UAE were optimized and modeled by the use of response surface methodology in order to maximize the yield of total phenolics and antioxidant capacity. The optimal operational parameters for the UAE procedure were determined to be 16.5 min, 74% (v/v) DES in water, and a solvent-to-solid ratio equal to 192. HPLC analysis, which was performed on the optimum extract, revealed significant levels of phenolics present in the aloe rind. Efficient recovery of the extracted antioxidants was obtained by the use of solid-phase extraction (SPE) and polyamide cartridges. The ChCl-CA DES exhibited excellent recycling capability with a yield of over 90% through SPE. Finally, the greenness of the method was evaluated using the green AGREE and AGREEprep metrics. The results highlighted the sustainability and the greenness of the proposed extraction procedure for the aloe by-product.

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.

Adsorptive Membranes Incorporating Ionic Liquids (ILs), Deep Eutectic Solvents (DESs) or Graphene Oxide (GO) for Metal Salts Extraction from Aqueous Feed

Water scarcity is a significant concern, particularly in arid regions, due to the rapid growth in population, industrialization, and climate change. Seawater desalination has emerged as a conventional and reliable solution for obtaining potable water. However, conventional membrane-based seawater desalination has drawbacks, such as high energy consumption resulting from a high-pressure requirement, as well as operational challenges like membrane fouling and high costs. To overcome these limitations, it is crucial to enhance the performance of membranes by increasing their efficiency, selectivity, and reducing energy consumption and footprint. Adsorptive membranes, which integrate adsorption and membrane technologies, offer a promising approach to address the drawbacks of standalone membranes. By incorporating specific materials into the membrane matrix, composite membranes have demonstrated improved permeability, selectivity, and reduced pressure requirements, all while maintaining effective pollutant rejection. Researchers have explored different adsorbents, including emerging materials such as ionic liquids (ILs), deep eutectic solvents (DESs), and graphene oxide (GO), for embedding into membranes and utilizing them in various applications. This paper aims to discuss the existing challenges in the desalination process and focus on how these materials can help overcome these challenges. It will also provide a comprehensive review of studies that have reported the successful incorporation of ILs, DESs, and GO into membranes to fabricate adsorptive membranes for desalination. Additionally, the paper will highlight both the current and anticipated challenges in this field, as well as present prospects, and provide recommendations for further advancements.

Combination of deep eutectic solvent and functionalized metal-organic frameworks as a green process for the production of 5-hydroxymethylfurfural and furfural from sugars

Biomass is an abundant and sustainable resource that can be converted into energy and chemicals. Therefore, the development of efficient methods for the conversion of biomass into platform intermediates is crucial. In this study, the one-pot conversion of sugars into 5-hydroxymethylfurfural (HMF) and furfural was achieved using the metal-organic framework combined with metal ions [MIL-101(Cr)] as a high-activity catalyst, and a deep eutectic solvent (choline chloride and lactic acid) as a green solvent. The optimal temperature, time, amount of catalyst used, and amount of deep eutectic solvent used were all determined. The highest HMF yield of 49.74% and furfural yield of 55.90% were obtained. The recyclability of the catalysts and deep eutectic solvent was also investigated. After three reaction runs, the HMF yield was still nearly 30.00%. Finally, the MIL-101(Cr) catalytic system was selected to study the kinetic mechanism underlying the conversion of glucose into HMF.

Optimization of green deep eutectic solvent (DES) extraction of Chenopodium quinoa Willd. husks saponins by response surface methodology and their antioxidant activities

Quinoa saponins have outstanding activity, and there are an increasing number of extraction methods, but there are few research programs on green preparation technology. The extraction conditions of quinoa saponins with deep eutectic solvents (DESs) were optimized by single-factor experiments combined with response surface methodology. The antioxidant capacity of saponins extracted by DESs and traditional methods was evaluated by the DPPH clearance rate, iron ion chelation rate and potassium ferricyanide reducing power. The results show that the optimal DES is choline chloride: 1,2-propylene glycol (1 : 1), and its water content is 40%. The optimal extraction conditions were as follows: the solid-to-solvent ratio was 0.05 g mL-1, the extraction time was 89 min, and the extraction temperature was 75 °C. Under these conditions, the extraction of quinoa saponins by DES was more effective than the traditional extraction methods. The saponins extracted by DES and traditional methods were analyzed by UPLC-MS, and five main saponins were identified. Quantitative analysis by HPLC-UV showed that Q1 (m/z = 971) and Q2 (m/z = 809) had higher contents of saponins. In vitro antioxidant experiments showed that all DES saponin extracts showed good antioxidant capacity. This study provides new insight into the development and utilization of quinoa saponins.

Towards a circular economy in virgin olive oil production: Valorization of the olive mill waste (OMW) "alpeorujo" through polyphenol recovery with natural deep eutectic solvents (NADESs) and vermicomposting

Virgin olive oil (VOO) production generates large amounts of a harmful by-product, olive mill waste (OMW) or alpeorujo, which has a strong environmental impact and that must be recycled to adapt VOO production to a circular economy model. Here, the valorization of OMW was studied by considering three consecutive stages: Stage 1 involves the generation of OMW; Stage 2 the recovery of bioactive phenolic compounds from the fresh OMW using natural deep eutectic solvents (NADESs), generating a valuable phenolic extract and a new by-product, a dephenolized OMW named "alpeoNADES"; and Stage 3 involves vermicomposting alpeoNADES with Eisenia fetida earthworms. Six NADES were formulated and tested, selecting a NADES composed of citric acid and fructose (CF) derived from food grade and biodegradable substances. CF was the most effective solvent to obtain phenolic extracts for nutraceutical and agronomical purposes, extracting 3988.74 mg/kg of polyphenols from fresh OMW. This alpeoNADES is a non-palatable substrate for E. fetida earthworms, as the residual CF gives it an acidic pH (pH 2). Its palatability was improved by mixing it with horse manure and straw for vermicomposting, in a 1:1 and 3:1 dry weight ratio. When these substrates were precomposted for 3 weeks they reached pH 5.5-6 and they could then be vermicomposted for 23 weeks (using OMW as a control). The best substrate for vermicomposting was determined by the worm biomass, growth rate, carbon to nitrogen (C:N) ratio, and N and P content. AlpeoNADES and manure 3:1 produced the highest quality vermicompost in the shortest time, generating a product that complied with European standards for organic fertilizers. Hence, alpeoNADES was recycled to a low-cost, organic balanced fertilizer in Stage 3, enabling the olive oil industry to transition to sustainable production through this integrated circular economy design.

Synthesis, characterization, DFT studies, and adsorption properties of sulfonated starch synthesized in deep eutectic solvent

In this study, sulfonated starch (SS) was successfully synthesized using sulfamic acid as a sulfonating agent in a deep eutectic solvent (DES). Four-factor and three-level orthogonal experiments were conducted to determine the optimal preparation conditions, which were found to be a molar ratio of starch to urea of 1:20, a reaction temperature of 90 °C, a reaction time of 5 h, and a stirring speed of 200 rpm. The sulfonation reaction mechanism was extensively studied using various techniques, including Fourier transform infrared spectroscopy, elemental analysis, X-ray diffraction, molecular weight, particle distribution, X-ray photoelectron spectroscopy, scanning electron microscopy, and DFT calculations. The results showed that the sulfonation reaction slightly damaged starch granules, occurred on the surface of starch granules, and on the O6 atoms of the glucose unit. SS exhibited a wide pH range of application (5-10), a fast adsorption rate (400 s to reach adsorption equilibrium), and a high adsorption capacity (118.3 mg/g) under optimal conditions. The adsorption process of SS for methylene blue followed the pseudo-first-order kinetic model and was consistent with the Langmuir model, which was endothermic and spontaneous. The adsorption process was attributed to hydrogen bonding and electrostatic interactions.

Advances in green solvents for production of polysaccharide-based packaging films: Insights of ionic liquids and deep eutectic solvents

The problems with plastic materials and the good film-forming properties of polysaccharides motivated research in the development of polysaccharide-based films. In the last 5 years, there has been an explosion of publications on using green solvents, including ionic liquids (ILs), and deep eutectic solvents (DESs) as candidates to substitute the conventional solvents/plasticizers for preparations of desired polysaccharide-based films. This review summarizes related properties and recovery of ILs and DESs, a series of green preparation strategies (including pretreatment solvents/reaction media, ILs/DESs as components, extraction solvents of bioactive compounds added into films), and inherent properties of polysaccharide-based films with/without ILs and DESs. Major reported advantages of these new solvents are high dissolving capacity of certain ILs/DESs for polysaccharides (i.e., up to 30 wt% for cellulose) and better plasticizing ability than traditional plasticizers. In addition, they frequently display intrinsic antioxidant and antibacterial activities that facilitate ILs/DESs applications in the processing of polysaccharide-based films (especially active food packaging films). ILs/DESs in the film could also be further recycled by water or ethanol/methanol treatment followed by drying/evaporation. One particularly promising approach is to use bioactive cholinium-based ILs and DESs with good safety and plasticizing ability to improve the functional properties of prepared films. Whole extracts by ILs/DESs from various byproducts can also be directly used in films without separation/polishing of compounds from the extracting agents. Scaling-up, including costs and environmental footprint, as well as the safety and applications in real foods of polysaccharide-based film with ILs/DESs (extracts) deserves more studies.

DES: their effect on lignin and recycling performance

Lignocellulosic biomass raw materials are renewable resources with abundant reserves in nature, and have many advantages, such as being green, biodegradable and cheap. Lignin, one of the three significant components of lignocellulose, possesses a chemical structure rich in phenylpropane and is a primary aromatic resource for the bio-based economy. For the extraction and degradation of lignin, the most common method is the pretreatment of lignocellulose with deep eutectic solvents (DES), which have similar physicochemical properties to ionic liquids (ILs) but address the disadvantages associated with ILs (DES have the advantages of low cost, low toxicity, and non-flammability). In lignocellulose pretreatment, a large amount of solvent is generally required to achieve the desired effect. However, after treatment, a substantial volume of solvent will be wasted, and thus, the problem of the recovery and reuse of DES solution needs to be adequately solved. The methods and mechanisms of perfect DES regeneration will be discussed from the perspective of the elemental composition and features of DESs in this review, which will also outline the present DES recovery methods, such as rotary evaporation, membrane separation, freeze-drying, electrodialysis, etc. The detailed process and the advantages and disadvantages of each method since 2018 are introduced in detail. Future DES recovery methods have been prospected, and the optimization of the functional properties of DESs after recovery is discussed. It is expected to find a convenient and efficient application method for DES extraction or degradation of lignin with low energy and low cost.

Glycerol and Natural Deep Eutectic Solvents Extraction for Preparation of Luteolin-Rich Jasione montana Extracts with Cosmeceutical Activity

Jasione montana is a plant from the family Campanulaceae rich in phenols with health-beneficial properties such as luteolin (LUT) derivatives. In this work, a glycerol-based ultrasound-assisted extraction method was developed and optimized for in total phenol (TP) and LUT content, as well as antiradical activity (RSA). The best conditions (glycerol content, temperature, plant material weight, and ultrasonication power) for the preparation of J. montana extracts richest in TP (OPT-TP), LUT (OPT-LUT), and having the best RSA (OPT-RSA) were determined. Furthermore, numerous natural deep eutectic solvents (NADES), containing proline, glycerol, betaine, urea, and glucose were prepared and used for the extraction of J. montana. Contents of TP, LUT, and RSA in the prepared extracts were established. Antioxidant and cosmeceutical activity of the prepared extracts was tested. The OPT-TP, OPT-LUT, and OPT-RSA, as well as the most efficient NADES-based extract, PG-50-TP, were excellent antioxidants and Fe²⁺ ion chelators. In addition, they were potent inhibitors of collagenase and hyaluronidase, as well as good significant anti-elastase and -lipoxygenase activity. The observed antioxidant- and enzyme-inhibiting activity of J. montana extracts prepared using environmentally friendly methods and non-toxic solvents makes them promising ingredients of cosmeceutical products.

Natural deep eutectic solvents in phytonutrient extraction and other applications

Natural deep eutectic solvents (NaDESs) are considered a new type of green solvent with attractive application prospects in many fields because of their simple preparation, low cost, environmental friendliness, low volatility, high solvency capacity, designable structure, and easy biodegradability. Due to their biocompatibility, they are safe to use and are particularly suitable for natural product applications. In recent years, NaDESs have been used to extract phytonutrients (e.g., flavonoids, saponins, polysaccharides, alkaloids, quinones, phenolic acids, volatile oils, etc.) to improve their solubility, stability, and bioavailability. This review is intended to summarize and discuss recent progress in the field of natural products related to materials and preparation methods, physicochemical properties, enhancing extraction and separation, increasing solubility, improving stability and bioavailability, facilitating oral absorption of phytonutrients, and finally, highlighting the challenge for future work.

Ultrasound-Assisted Extraction of Flavonoids from Potentilla fruticosa L. Using Natural Deep Eutectic Solvents

A series of natural deep eutectic solvents (NADESs) were prepared with choline chloride, betaine, and a variety of natural organic acids in order to find new environmentally-friendly green solvents to replace the traditional solvents. The NADESs were employed to extract flavonoids from Potentilla fruticosa L. (PFL) with the help of ultrasound. The eutectic solvent diluted with an appropriate amount of water improved the extraction ability of flavonoids due to the decrease of solution viscosity. The microstructure of the raw sample and the samples subjected to ultrasonic bath in different solutions were observed using scanning electron microscope (SEM) to determine the role of the NADESs in the extraction process. The DPPH method and glucose consumption method were used to study the antioxidant and hypoglycemic ability of flavonoid compounds in PFL. Single factor method and response surface methodology (RSM) were designed to analyze the effects of three extraction parameters, including solvent/solid ratio, ultrasonic power, and extraction time, on the extraction yield, antioxidant capacity, and hypoglycemic capacity, and the corresponding second-order polynomial prediction models were established. The optimal extraction conditions for the maximum extraction yield, antioxidant capacity, and hypoglycemic capacity were predicted by RSM, and the reliability of RSM simulation results was verified by a one-off experiment.

Extraction of bioactive compounds from Dipsacus fullonum leaves using deep eutectic solvents

In this study, deep eutectic solvent (DES) based systems were evaluated for selective extraction and optimized for increased recovery of chlorogenic acid derivatives, flavone glycosides and iridoid glycosides from Dipsacus fullonum L. leaves. Bioactives from Dipsacus plants has shown great antioxidant and antimicrobial activities as well as effectiveness against several cancer strains and a source for anti-Borrelia compounds. Twelve different hydrophilic and hydrophobic DESs were tested to find the best solvent composition. Choline chloride and betaine were used as hydrogen bond acceptors (HBA) for the preparation of hydrophilic DESs and menthol for hydrophobic DESs. The tested hydrogen bond donors (HBD) were various organic acids and glycerol. The composition of most effective DES was optimized using the Box-Behnken design for each of the three main group of analytes from D. fullonum L. to evaluate possible selectivity and highest recovery. HPLC-DAD-MS was used to identify and quantify the main bioactive compounds extracted from plant material. The optimal extraction for highest overall recovery was achieved using a molar ratio of choline chloride and lactic acid of 1:2.4 with 35% water and 27 mL of the solvent per one gram of dry material. The optimized DES extract gave concentrations 1.8 to 2.2 times higher than traditional organic solvent extracts depending on the group of analytes.

Structure and physicochemical properties of polysaccharides from Poria cocos extracted by deep eutectic solvent

Poria cocos, a famous traditional Chinese medicine and a well-known food or food supplement, has shown therapeutic potential against cancer and the uneasiness of the mind. In addition, polysaccharides (PCPs) in this fungus were found to be various bioactive. In this work, one such PCP, PCP-1, extracted by deep eutectic solvent (DES) and separated using Sephadex G-15 columns, was characterized using GC-MS, HPGPC, FT-IR, and NMR, while also tested for physicochemical properties. Results indicated that PCP-1 contained 96.89 ± 3.21% total sugars and was a glucan with molecular weight of 3.2 kD. The main glycosidic linkage was 1,3-linked Glcp with 96.82 mol% content and a triple helix structure, and β-D-Glcp-(1 → linkage connected to the main chain through an O-6 atom was the backbone structure. In terms of the physicochemical property, PCP-1 was soluble in water, but not in organic solvent, and processed a relative high water-holding capacity (8.64 ± 0.14 g/g) and low oil-holding capacity (2.52 ± 0.21 g/g). In addition, in vitro, PCP-1 was found to have the ability of scavenging DPPH, hydroxyl free radical, superoxide anion radical and reducing ferric at different levels. This research would be useful for the further application of PCP-1.

Development of Green and Efficient Extraction of Bioactive Ginsenosides from Panax ginseng with Deep Eutectic Solvents

The extraction of active constituents from natural sources in a green and efficient manner is considered an important field in the pharmaceutical industry. In recent years, deep eutectic solvents (DESs), a new type of green solvent, have attracted increasing attention. Therefore, we aimed to establish a green and high-efficiency extraction method for ginsenosides based on DESs. This study takes Panax ginseng as a model sample. Eighteen different DESs were produced to extract polar ginsenosides. Ultrasound-assisted extraction (UAE) was applied for simplicity and efficiency. A binary DES synthesized using choline chloride and urea at a proportion of 1:2 prepared by a heating stirring method is proven to be more effective than other solvents, such as the widely used 70% ethanol for the extraction of ginsenosides. Three variables that might affect the extraction, including the DES content in the extraction solvent, liquid/solid ratio, and ultrasound extraction time, were evaluated for optimization. The optimum extraction conditions for ginsenosides were determined as follows: DES water content of 20 wt%, liquid/solid ratio of 15 mL g⁻¹, and an ultrasonic extraction time of 15 min. The extraction yield for the optimized method is found to be 31% higher than that for 70% ethanol, which achieves efficient extraction. This study shows that DESs are available to extract ginsenosides for use in traditional Chinese medicine. The discovery also contributes to further research into the green extraction of ginsenosides.

Effects of five extraction methods on total content, composition, and stability of flavonoids in jujube

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Five methods of extracting flavonoids from jujube were compared in different aspects.

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The extraction methods can significantly influence the flavonoid compositions.

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DES-UAE method had outstanding ability to maintain the stability of flavonoids.

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DES-UAE is an efficient and green method for extracting flavonoids from jujube.

The present study investigated the effects of different extraction methods including water-water bath (W-WB), ethanol-water bath (E-WB), deep eutectic solvent (DES) combined with ultrasound-assisted extraction (DES-UAE), microwave-assisted extraction (DES-MAE), and enzyme-assisted extraction (DES-EAE) on flavonoids (total flavonoid content, flavonoid composition, and stability) in jujube. The highest total flavonoid content of 8.03 mg/g was obtained by the DES-MAE extraction. Fifteen types of flavonoids were identified from jujube. The amount of rutin produced by the E-WB and DES-UAE methods was 66.88 ± 1.58 μg/g and 45.23 ± 3.22 μg/g, respectively. The retention of flavonoids in DES-UAE extracts were 98.15 ± 0.51%, 64.25 ± 2.21% after 2 h of high temperature treatment at 90 °C and 21 days of dark storage, respectively. The flavonoids extracted by different methods were suitable for dark storage under different light contrasts, where the retention of flavonoids extracted by DES-UAE method was 86.44 ± 2.45%. In conclusion, DES-UAE would be an efficient method for flavonoid extraction from jujube.

Extraction of Polyphenolic Antioxidants from Red Grape Pomace and Olive Leaves: Process Optimization Using a Tailor-Made Tertiary Deep Eutectic Solvent

In the framework of introducing green strategies for food processing, the industrial orientation has shifted towards the replacement of conventional petroleum-based solvents with alternative eco-friendly ones. On this basis, the objective of this study was to synthesize a novel, tertiary, food-grade deep eutectic solvent, composed of glycerol, citric acid, and L-proline (GL-CA-Pro), and to test it as a solvent for the extraction of polyphenols from agri-food waste biomass. After an initial screening on various common residual materials (apple peels, lemon peels, orange peels, red grape pomace, olive leaves), evidence emerged that indicated GL-CA-Pro was more effective than other DESs commonly used for polyphenol extraction. Furthermore, extracts from red grape pomace (RGP) and olive leaves (OLL) were shown to contain higher level of total polyphenols and increased antioxidant activity. Process optimization for those two materials with the response surface methodology revealed that the major difference pertained to the extraction time. In addition, for both materials, GL-CA-Pro was shown to provide higher total polyphenol yields (53.25 and 42.48 mg gallic acid equivalents per g of dry mass, respectively) compared to water and 60% aqueous ethanol. However, the chromatographic analyses for OLL suggested aqueous ethanol was a more suitable solvent for some principal polyphenolic constituents. The RGP extract produced with GL-CA-Pro exhibited significantly stronger antioxidant effects compared to the aqueous and hydroethanolic extracts, but the outcome for the OLL extracts was diversified. It was concluded that GL-CA-Pro is a very efficient solvent for RGP polyphenols, but its efficiency regarding OLL was comparable to that of aqueous ethanol.

Three-phase partitioning, a recyclable method for the purification of R-phycoerythrin from a red algae Porphyra yezoensis

In this study, R-phycoerythrin (R-PE) was isolated and characterized from Porphyra yezoensis by three-phase partitioning (TPP) method. The effects of temperature, time, pH, salt saturation, and volume ratio on the purity and recovery rate of R-PE were studied. The optimum extraction conditions were determined as follows: salt saturation of 70%, temperature of 25 °C, time of 45 min, pH of 7.0, and volume ratio of 1:1. Under the optimal extraction conditions, the purity of R-PE was 3.90. The results of SDS-PAGE showed that R-PE has three bands at 23 kDa, 22 kDa, and 18 kDa, corresponding to its α, β, γ subunits. The structure and optical activity of R-PE did not change before and after purification based on ultraviolet, infrared, and fluorescence spectra. In addition, the purity and recovery rate of R-PE extracted by tert-butanol were evaluated. The results showed that the extraction performance of tert-butanol for R-PE remained unchanged in three recoveries. These show that TPP is an efficient, green, and recyclable extraction technology.

Neoteric deep eutectic solvents: history, recent developments, and catalytic applications

Deep eutectic solvents (DESs) are modified versions of ionic liquids (ILs) and are formed by the fusion of polar components (liquids or solids) via hydrogen bonding interactions. DESs are prepared by the simple mixing of two or three cheap constituents (that are capable of self-association) with gentle heating, which leads to a drastic decrease in their melting points. The resultant clear homogeneous mixture consists of cations, anions, as well as neutral molecules; this will contribute both ionic and molecular solvent properties to the DESs. DESs have emerged as alternatives to conventional organic solvents and ILs, which meet different criteria such as availability, low cost, low toxicity, biodegradability, recyclability, ease of preparation method, tunable, and designer physiochemical properties. Many of them have attracted considerable attention and haave been applied in distinct fields of chemistry. To summarize the full-scale development of DESs, this review discusses the history, classifications, various methods of preparation, properties, and some major applications in catalysis in the last three years. This review is expected to be helpful for the further development of DESs based on a summary of the fundamental research in the field.

Cellulose Membranes in the Treatment of Spent Deep Eutectic Solvent Used in the Recovery of Lignin from Lignocellulosic Biomass

Ultrafiltration was employed in the purification of spent Deep Eutectic Solvent (DES, a mixture of choline chloride and lactic acid, 1:10, respectively) used in the extraction of lignin from lignocellulosic biomass. The aim of this was to recover different lignin fractions and to purify spent solvent. The results revealed that the commercial regenerated cellulose membranes—RC70PP and Ultracel 5 kDa UF membranes—could be used in the treatment of the spent DES. The addition of cosolvent (ethanol) to the spent DES decreased solvent’s viscosity, which enabled filtration. With two-pass ultrafiltration process with 10 kDa and 5 kDa membranes about 95% of the dissolved polymeric compounds (lignin and hemicelluloses) were removed from the spent DES. The utilized membranes also showed the capability to fractionate polymeric compounds into two fractions—above and under 10,000 Da. Moreover, the 10 kDa cellulose-based membrane showed good stability during a continuous period of three weeks exposure to the solution of DES and ethanol. Its pure water permeability decreased only by 3%. The results presented here demonstrate the possibility to utilize cellulose membranes in the treatment of spent DES to purify the solvent and recover the interesting compounds.

Study on enhanced extraction and seasonal variation of secondary metabolites in Eucommia ulmoides leaves using deep eutectic solvents

It has been considered as a crucial field for the extraction of active ingredients from herbal medicine to use a green and efficient method in the medicinal and food industries. In recent years, deep eutectic solvents (DESs) have been obtaining increase attention in green chemistry area since its sustainability, safety and biodegradability. In this study, an efficient DES composed of choline chloride and L-(+)-ascorbic acid with a molar ratio of 2:1 performed higher efficacy on the extraction of target compounds (including iridoids, phenolic acids and flavonoids) in Eucommia ulmoides leaves than 50% methanol solution. Considering the extraction efficacy and time consumption, microwave-assisted extraction (MAE) was selected and the operational conditions, including power of microwave, liquid/solid ratio and irradiation time were optimized by response surface methodology (RSM). Water was used as anti-solvent to recover ten target analytes from DES with recovery yields of 97.59%, 94.91%, 96.09%, 90.66%, 95.16%, 87.33%, 86.57%, 82.15%, 89.28% and 80.75% for eucommiol (EU), aucubin (AU), geniposidic acid (GA), chlorogenic acid (CA), asperuloside (AP), rutin (RU), kaempferol-3-O-sambubioside (KS), isoquercitrin (IQ), kaempferol-3-O-rutinoside (KR) and astragaline (AS), respectively. By combining the DES-based MAE and quantitative analysis of multi-components by single mark (QAMS) methods, the contents of ten compounds in the leaves of Eucommia ulmoides were determined to clarify the relationship between the accumulation of secondary metabolites and the harvest period. It was found that the contents of main ingredients reached the highest during May to October. The period appears to be the best harvest period for Eucommia ulmoides leaves. This study provides a novel strategy for the harvesting, processing, and quality control of the raw materials from Eucommia ulmoides leaves.

Natural deep eutectic solvents as tailored and sustainable media for the extraction of five compounds from compound liquorice tablets and their comparison with conventional organic solvents

An efficient and environmentally friendly ultrasound-assisted (UAE) natural deep eutectic solvent (NADES) extraction method was applied for the extraction of five bioactive compounds (liquiritin, isoliquiritin, liquiritigenin, glycyrrhizic acid and isoliquiritigenin) from compound liquorice tablets (CPLTs), and the antioxidant activities of these compounds were evaluated. In this study, eighteen different NADES systems based on either two or three components were tested and a 1,4-butanediol–levulinic acid system (1 : 3 molar ratio) was selected as a topgallant solvent for maximizing analyte extraction yields. Various extraction parameters, such as water content, liquid/solid ratio, extraction time and temperature, were systematically optimized by single-factor and response surface methodology (RSM) experiments. The results indicated that the optimum extraction conditions for the analytes featured a water content of 17%, a liquid/solid ratio of 42 mL g⁻¹ and an extraction time of 30 min. The extracted amounts of liquiritin, isoliquiritin, liquiritigenin, glycyrrhizic acid and isoliquiritigenin reached 5.60, 3.17, 1.27, 74.62 and 1.34 mg g⁻¹, respectively, under optimized conditions, which were much higher than those extracted using conventional organic solvents. In addition, antioxidant tests revealed that the NADES extracts showed higher DPPH and hydroxyl radical-scavenging capacity than the conventional solvent extracts used for comparison. This study provides a suitable approach for efficiently extracting the bioactive compounds of CPLTs. Meanwhile, NADESs can be extended to other natural products as green extraction media.

A 1,4-butanediol–levulinic acid system was selected as a topgallant solvent and extraction parameters were optimized. NADES extracts exhibited higher extraction efficiency and in vitro antioxidant activities than conventional solvent extracts.

Deep Eutectic Solvents (DESs) as Green Extraction Media of Beneficial Bioactive Phytochemicals

Deep eutectic solvents (DES) are a mixture of two or more components and are classified as ionic solvents with special properties such as low volatility, high solubility, low melting points, low-cost materials and are less toxic to humans. Using DES has been suggested as an eco-friendly, green method for extraction of bioactive compounds from medicinal plants and are a safe alternative for nutritional, pharmaceutical and various sector applications. Conventional solvent extraction methods present drawbacks such as long extraction period, safety issues, harmful to the environment, costly and large volume of solvents required. The extraction method with DES leads to higher extraction yield and better bioactivity results as compared to the conventional solvents. This review provides a summary of research progress regarding the advantages of using DES to extract bioactive compounds such as phenolic acid, flavonoids, isoflavones, catechins, polysaccharides, curcuminoids, proanthocyanidin, phycocyanin, gingerols, ginsenosides, anthocyanin, xanthone, volatile monoterpenes, tannins, lignin, pectin, rutin, tert-butyl hydroquinone, chlorogenic acids, resveratrol and others, as opposed to using conventional solvents. The bioactivity of the extracts is determined using antioxidant, antibacterial and antitumor activities. Hence, DESs are considered potential green media with selective and efficient properties for extracting bioactive ingredients from medicinal plants.

Efficient extraction of bioactive flavonoids from Celtis sinensis leaves using deep eutectic solvent as green media

In recent years, deep eutectic solvent (DES) has attracted comprehensive attention on the extraction of natural products, and is regarded as an alternative to traditional organic solvents for the environmental advantages. Twenty-six DESs were compared for their extraction yield of total flavonoids and isovitexin (the main flavonoid in Celtis sinensis) from Celtis sinensis. The results show that the extraction yields of total flavonoids by betaine/glycolic acid (DES8), ethylamine hydrochloride/1,2-propanediol (DES12) and tetrapropylammonium bromide/lactic acid (DES17) are the highest, while the extraction yields of isovitexin by ethylene glycol/malonic acid (DES23), ethylene glycol/glycolic acid (DES24) and 1,2-propanediol/glycolic acid (DES26) are the highest. The extraction conditions using the above six DESs were further optimized systematically. Under optimum conditions, the extraction rates of total flavonoids and isovitexin can be increased up to 95.39 and 10.58 mg g⁻¹, respectively, which were significantly higher than that of methanol extraction. In order to exclude the effect of DESs on the bioactivity of Celtis sinensis extract, the macroporous resin D-101 was used to purify the total flavonoids from DESs extract, and the recovery rates of flavonoids from the above six kinds of DESs were all over 80%. Next, the anti-inflammatory activity of DES extracts was compared using a lymphocyte transformation experiment. The result showed that the inhibition rate of the DES24 extract on the proliferation of Con A-activated T cells was up to 72% with an IC₅₀ value of 124.8 μg mL⁻¹. None of the DESs extracted exhibited cytotoxicity on normal T cells. The mechanism of the anti-inflammatory activity against Con A-activated T cells may be that DES24 flavonoids extract induced the apoptosis of inflammatory T cells, and activated the expression of pro-apoptotic protein. Taken together, DES has showed significant advantages on the extraction of natural products for the relatively mild extraction condition, high yield and environmental-friendliness.

In recent years, deep eutectic solvent (DES) has attracted comprehensive attention on the extraction of natural products, and is regarded as an alternative to traditional organic solvents for the environmental advantages.

Lipase-Catalyzed Production of Sorbitol Laurate in a "2-in-1" Deep Eutectic System: Factors Affecting the Synthesis and Scalability

Surfactants, such as glycolipids, are specialty compounds that can be encountered daily in cleaning agents, pharmaceuticals or even in food. Due to their wide range of applications and, more notably, their presence in hygiene products, the demand is continuously increasing worldwide. The established chemical synthesis of glycolipids presents several disadvantages, such as lack of specificity and selectivity. Moreover, the solubility of polyols, such as sugars or sugar alcohols, in organic solvents is rather low. The enzymatic synthesis of these compounds is, however, possible in nearly water-free media using inexpensive and renewable building blocks. Using lipases, ester formation can be achieved under mild conditions. We propose, herein, a "2-in-1" system that overcomes solubility problems, as a Deep Eutectic System (DES) made of sorbitol and choline chloride replaces either a purely organic or aqueous medium. For the first time, 16 commercially available lipase formulations were compared, and the factors affecting the conversion were investigated to optimize this process, owing to a newly developed High-Performance Liquid Chromatography-Evaporative Light Scattering Detector (HPLC-ELSD) method for quantification. Thus, using 50 g/L of lipase formulation Novozym 435® at 50 °C, the optimized synthesis of sorbitol laurate (SL) allowed to achieve 28% molar conversion of 0.5 M of vinyl laurate to its sugar alcohol monoester when the DES contained 5 wt.% water. After 48h, the de novo synthesized glycolipid was separated from the media by liquid-liquid extraction, purified by flash-chromatography and characterized thoroughly by one- and two-dimensional Nuclear Magnetic Resonance (NMR) experiments combined to Mass Spectrometry (MS). In completion, we provide initial proof of scalability for this process. Using a 2.5 L stirred tank reactor (STR) allowed a batch production reaching 25 g/L in a highly viscous two-phase system.

Determination of Suitable Macroporous Resins and Desorbents for Carnosol and Carnosic Acid from Deep Eutectic Solvent Sage (Salvia officinalis) Extract with Assessment of Antiradical and Antibacterial Activity

In this study, for the first time, the adsorption/desorption characteristics of carnosic acid and carnosol from deep eutectic solvent extract of Salvia officinalis on five macroporous resins (HP20, XAD7HP, XAD16N, HP21, HP2MG) were evaluated. The high adsorption and medium desorption capacities of carnosic acid and carnosol as well as antibacterial and antiradical activity from the extract obtained with choline chloride:lactic acid (1:2) on XAD7HP resin indicated that resin was appropriate. To get the optimal separation process, the influence of factors such as adsorption/desorption time and volume of desorbent was further investigated. The results showed that the extract with high antiradical and antibacterial activity was obtained via adsorption and desorption on XAD7HP resin. The extraction efficiencies of the deep eutectic solvents (DESs) recycled once, twice, and thrice were 97.64% (±0.03%), 93.10% (±0.66%), and 88.94% (±1.15%), respectively, for carnosic acid, and 96.63% (±0.04%), 94.38% (±0.27%), and 91.19% (±0.36%), respectively, for carnosol, relative to the initial solvent efficiency. Based on that, this method is a promising basis for the large-scale preparation of extracts from Salvia officinalis with further application in the pharmaceutical or food industry, especially for maintaining the “green” character of the whole process to obtain the appropriate extract.

Ultrasound-assisted biomass valorization to industrial interesting products: state-of-the-art, perspectives and challenges

Nowadays, the application of ultrasound (US) energy for assisting the lignocellulosic biomass and waste materials conversion into value-added products has dramatically increased. In this sense, this review covers theoretical aspects, promising applications, challenges and perspectives about US and its use for biomass treatment. The combination of US energy with a suitable reaction time, temperature and solvent contributes to the destruction of recalcitrant lignin structure, allowing the products to be used in thermochemical and biological process. The main mechanisms related to US propagation and impact on the fragmentation of lignocellulosic materials, selectivity, and yield of conversion treatments are discussed. Moreover, the synergistic effects between US and alternative green solvents with the perspective of industrial applications are investigated. The present survey analysed the last ten years of literature, studying challenges and perspectives of US application in biorefinery. We were aiming to highlight value-added products and some new areas of research.

Optimization of Extraction of Bioactive Compounds from Baphicacanthus cusia Leaves by Hydrophobic Deep Eutectic Solvents

Deep eutectic solvents (DESs) are considered as efficient and green solvents for the extraction of bioactive compounds from medicinal plants. In this work, a novel method of DES-based ultrasound-assisted extraction of bioactive compounds from Baphicacanthus cusia leaves (BCL) was established. Systematic screening and the morphology of the original and treated BCL were observed with scanning electron microscopy to determine the extraction efficiency of different solvents. The extraction conditions were optimized by Box–Behnken design (BBD) tests and the optimal extraction conditions were as follows: lactic acid/L-menthol ratio of 5: 2 (mol/mol), solid–liquid ratio of 80.0 mL/g and temperature of 60.5 °C. The extraction yields of tryptanthrin, indigo and indirubin reached 0.356, 1.744 and 0.562 mg/g, respectively. The results of a 2,2-diphenyl-1-picrylhydrazy (DPPH) radical scavenging activity test indicated the feasibility of DESs in the extraction of bioactive compounds. This study indicated that L-menthol/lactic acid was a green and efficient solvent for the extraction of bioactive compounds from BCL, and DES-based ultrasound-assisted extraction could be used as an effective application strategy for the extraction of bioactive compounds from medicinal plants.

Removing Acrylic Conformal Coating with Safer Solvents for Re-Manufacturing Electronics

Conformal coating is typically composed of polymeric film and is used to protect delicate electronic components such as printed-circuit boards. Without removing conformal coating, it would be difficult to repair these complicated electronics. Methylene chloride, also called dichloromethane (DCM), has a widespread usage in conformal coating stripper products. The high toxicity of DCM increases human health risk when workers are exposed to DCM during the conformal coating removal processes. Therefore, the replacement of DCM would be beneficial to greatly improve the overall safety profile for workers in the electronics and coating industries. This research identified and evaluated alternative chemicals for replacing DCM used in acrylic conformal coating stripping operations. The solubility of an acrylic conformal coating was measured and characterized using Hansen solubility parameters (HSP) theory. Coating dwell time tests using various solvent blends verified the accuracy of the created HSP solubility sphere. A data processing method was also developed to identify and screen potential alternative solvent blends in terms of safety, toxicity, and cost-effectiveness. The identified safer solvent blends were demonstrated to provide equivalent stripping performance as compared to DCM based coating strippers within an acceptable cost range. The results of this research will be of value to other types of conformal coatings, such as silicone and polyurethane, where DCM is commonly used in similar coating stripping operations. By safely removing conformal coating, delicate electronics would be available for re-manufacturing, enabling a circular economy.

Eutectic solvents with tuneable hydrophobicity: lipid dissolution and recovery

Despite the promising advantages of eutectic solvents, the application of these solvents as an extraction solvent is still limited due to the challenging product recovery. Previously, it was reported that lipids could be recovered from a hydrophobic eutectic solvent with the principle of switchable hydrophobicity. However, this method still involves additional chemicals, such as polymeric amines, water, and CO2, which need to be removed later. In this study, we proposed a different approach by shifting the hydrophobicity spectrum of a semi-hydrophobic solvent. Made of hydrophilic imidazole and hydrophobic hexanoic acid, this combination showed tuneable hydrophobicity when the composition was changed, shown by the change of dipolarity (π*) scale from solvatochromic analysis. At low imidazole content, the solvent was able to dissolve sunflower oil and algae oil, whereas, at high imidazole content, the solvent showed high affinity towards water. By adding imidazole to the solution of oil and the solvent, a phase split was induced between the oil-rich upper phase and the solvent-rich lower phase. With this approach, ∼75% of recovery efficiency was achieved for the two oils, with the purity of ∼100% for sunflower oil and 86% for algae oil.

Greener, Faster, Stronger: The Benefits of Deep Eutectic Solvents in Polymer and Materials Science

Deep eutectic solvents (DESs) represent an emergent class of green designer solvents that find numerous applications in different aspects of chemical synthesis. A particularly appealing aspect of DES systems is their simplicity of preparation, combined with inexpensive, readily available starting materials to yield solvents with appealing properties (negligible volatility, non-flammability and high solvation capacity). In the context of polymer science, DES systems not only offer an appealing route towards replacing hazardous volatile organic solvents (VOCs), but can serve multiple roles including those of solvent, monomer and templating agent-so called "polymerizable eutectics." In this review, we look at DES systems and polymerizable eutectics and their application in polymer materials synthesis, including various mechanisms of polymer formation, hydrogel design, porous monoliths, and molecularly imprinted polymers. We provide a comparative study of these systems alongside traditional synthetic approaches, highlighting not only the benefit of replacing VOCs from the perspective of environmental sustainability, but also the materials advantage with respect to mechanical and thermal properties of the polymers formed.

A solidified floating organic drop-dispersive liquid–liquid microextraction based on in situ formed fatty acid-based deep eutectic solvents for the extraction of benzophenone-UV filters from water samples

A method for simultaneous P_4,4,4,12Br–DecA deep eutectic solvent formation and UV filter extraction was developed.

Extraction assisted by far infrared radiation and hot air circulation with deep eutectic solvent for bioactive polysaccharides from Poria cocos (Schw.) wolf

In this study, a new ternary choline chloride-deep eutectic solvent was used to efficiently extract bioactive polysaccharides from poria cocos assisted by the new tool of the far infrared radiation (FIR) together with hot air circulation (HAC).

Microextraction Techniques with Deep Eutectic Solvents

In this review, the ever-increasing use of deep eutectic solvents (DES) in microextraction techniques will be discussed, focusing on the reasons needed to replace conventional extraction techniques with greener approaches that follow the principles of green analytical chemistry. The properties of DES will be discussed, pinpointing their exceptional performance and analytical parameters, justifying their current extensive scientific interest. Finally, a variety of applications for commonly used microextraction techniques will be reported.

Deep Eutectic Solvents: A Review of Fundamentals and Applications

Deep eutectic solvents (DESs) are an emerging class of mixtures characterized by significant depressions in melting points compared to those of the neat constituent components. These materials are promising for applications as inexpensive "designer" solvents exhibiting a host of tunable physicochemical properties. A detailed review of the current literature reveals the lack of predictive understanding of the microscopic mechanisms that govern the structure-property relationships in this class of solvents. Complex hydrogen bonding is postulated as the root cause of their melting point depressions and physicochemical properties; to understand these hydrogen bonded networks, it is imperative to study these systems as dynamic entities using both simulations and experiments. This review emphasizes recent research efforts in order to elucidate the next steps needed to develop a fundamental framework needed for a deeper understanding of DESs. It covers recent developments in DES research, frames outstanding scientific questions, and identifies promising research thrusts aligned with the advancement of the field toward predictive models and fundamental understanding of these solvents.