Ionic liquids and deep eutectic mixtures: sustainable solvents for extraction processes

Deep eutectic solvents in analysis, delivery and chemistry of pharmaceuticals

Deep eutectic solvents (DES) have an emerging scientific role, assisting modern pharmaceutics. They are uniquely supporting the resolution of crucial issues, such as the effective extraction and isolation of bio-actives. They act as media and catalysts for pharmaceutical drug synthesis, and as green solvents and modifiers in pharmaceutical analysis. Their role in pharmaceutical formulation and drug delivery is also up-and-coming, for instance, as alternative drug-solubilizing agents, drug stabilizers and functional additives, as therapeutic deep eutectic solvents, deep eutectic API, and monomers and reaction media for the synthesis of biomaterials for advanced drug delivery. The DES also help transforming medicinal/pharmaceutical chemistry. Although DES were described in 1918, their first pharmaceutical use is only reported in 1960. In view of their broad applicability in pharmaceutics, it may be interesting to review their history, origin, evolution, potential advantages, limitations, and specific applications as green solvents. A chronological and comparative study of the literature showed the important role of DES in green approaches for modern pharmaceuticals. The concepts, applications, and outcomes of DES in pharmaceutical analysis, formulation/drug delivery, and pharmaceutical/medicinal chemistry are presented. A comprehensive outline of the atypical applications of DES as effective green solvents in pharmaceutical bioactive extraction was assessed. Efforts to present classifications of DES explored in pharmaceuticals were also made. The present manuscript also covers computational trend, adds on commercial aspects with potential future applications of DES in pharmaceutical sciences.

New Horizon in Selective Tocols Extraction from Deodorizer Distillates Under Mild Conditions by Using Deep Eutectic Solvents

Tocols are commonly known as vitamin E, which comprise tocopherols and tocotrienols. Although vegetable oils are natural sources of tocols, deodorizer distillates (DDs) are attractive feedstock due to their potential abundance from oil refining processes and economic price. Deep eutectic solvents (DESs) are a family of neoteric solvents that show promising performance for tocols extraction. Besides their characters occupying the green chemistry concept, this review presents the current research on the potential performances of DESs in extracting tocols selectively and efficiently from DDs. The application of DESs in tocols extraction is presented considering three different ways: mono-phasic, in situ DESs formation, and bi-phasic systems. The basic principles of intermolecular interactions (H-bond, van der Walls bond, and misfit interaction) between DESs or their components with tocols are discussed to understand the mechanism by which DESs selectively extract tocols from the mixture. This is mainly observed to be a function of the intrinsic properties of DESs and/or tocols, which could be beneficial for tuning the appropriate DESs for extracting tocols selectively and effectively under mild operation conditions. This review is expected to provide insight in the potential application of DESs in the extracting of natural compounds with a phenolic structure and also briefly discusses the toxicity of DESs.

Exploring the Potential of PEG-Based Deep Eutectic Solvents as a Sustainable Alternative for Extraction of Biological Macromolecules Bovine Serum Hemoglobin

In recent years, deep eutectic solvents (DESs) have garnered significant attention as promising green alternatives to conventional organic solvents for a wide range of applications. In this study, four novel polyethylene glycol (PEG)-based DESs were prepared and evaluated for their physicochemical properties, including density, dynamic viscosity, and kinematic viscosity. Fourier transform infrared spectroscopy (FT-IR) and NMR analyses revealed substantial intermolecular interactions between the hydrogen bond donor and hydrogen bond acceptor components, confirming the formation of stable DES systems. The application of the prepared DESs was tested in biological separation, specifically for the selective extraction of bovine serum hemoglobin (BHb). This study demonstrates the efficacy of PEG-based DESs in selectively extracting BHb. Among the DESs studied, DES-4 (PEG-600) achieved the highest extraction efficiency of 88%, while maintaining protein stability. Spectroscopic techniques, including UV-visible, fluorescence, dynamic light scattering, circular dichroism, and FT-IR, were employed to investigate the extraction mechanism, conformational changes in protein structure, and DES-protein interactions. These methods provided insights into the structural stability and functionality of BHb during the extraction process. The physicochemical characterizations confirmed the unique properties of PEG-based DESs, making them viable candidates for sustainable protein extraction. Their compatibility, excellent extraction efficiency, and short separation times underscore their potential as environmentally friendly and long-lasting substitutes for conventional separation techniques. This study highlights the advancement of DESs in green chemistry and biotechnological applications, offering an efficient and sustainable platform for protein extraction while maintaining structural integrity.

Enhanced furfural extraction using neoteric hydrophobic solvents for sustainable biomass recovery and bioenergy applications

The recovery of furfural from hemicellulosic biowastes is important for developing sustainable and renewable energy alternatives to fossil fuels. However, current methods are inefficient and environmentally questionable. To address this issue, this study introduces neoteric hydrophobic solvents, specifically deep eutectic solvents (DESs) and ionic liquids (ILs). Of the 32 solvents tested, thymol:decanoic acid 1:1 (Thy:DecA) DES and trihexyltetradecyl phosphonium bis(trifluoro methylsulfonyl) imide [P14,6,6,6][NTf2] IL were the most effective, with extraction efficiencies of 94.1% and 97.1%, respectively. These solvents outperformed the reference solvent toluene, with an efficiency of 81.2%, while also showing favorable characteristics in multiple investigated criterions. For the first time, excellent performance stability was demonstrated under various operational conditions and reusability over multiple extraction and regeneration cycles. Furthermore, to provide insights into the molecular mechanisms of extraction, computational quantum chemistry modeling was employed, which showed a strong agreement with the experimental results. The development of these new neoteric solvents for furfural recovery from biowaste offers a highly effective, sustainable, and eco-friendly alternative to traditional solvents, representing a significant breakthrough in the field of renewable bioenergy production and sustainable materials recovery.

Enantiomeric separation of nefopam and cathinone derivatives using a supramolecular deep eutectic solvent as a chiral selector in capillary electrophoresis

The present study investigates the utilization of a supramolecular deep eutectic solvent (SUPRADES), consisting of sulfated-β-cyclodextrin (S-β-CD) and citric acid (CA), as a chiral selector (CS) in capillary electrophoresis for the enantiomeric separation of nefopam (NEF) and five cathinone derivatives (3-methylmethcathinone [3-MMC], 4-methylmethcathinone [4-MMC], 3,4-dimethylmethcathinone [3,4-DMMC], 4-methylethcathinone [4-MEC], and 3,4-methylendioxycathinone [MDMC]). A significant improvement in enantiomeric separation of the target analytes was observed upon the addition of S-β-CD-CA to the background electrolyte (BGE), leading to a baseline separation of all analytes. In particular, the optimum percentage of S-β-CD-CA, added to the BGE, was determined to be 0.075% v/v for NEF (Rs = 1.5) and 0.050% v/v for three out of five cathinone derivatives (Rs = 1.5, 1.6, and 2.4 for 3-MMC, 4-MEC, and 3,4-DMMC, respectively). In the case of 4-MMC and MDMC, a higher percentage of the CS, equal to 0.075% and 0.10% v/v, respectively, was required to achieve baseline separation (Rs = 1.5, 1.9 for MDMC and 4-MMC, respectively). The outcomes of the present study highlight the potential effectiveness of using SUPRADES as a CS in electrophoretic enantioseparations.

Reshaping Capillary Electrophoresis With State-of-the-Art Sample Preparation Materials: Exploring New Horizons

Capillary electrophoresis (CE) is a powerful analysis technique with advantages such as high separation efficiency with resolution factors above 1.5, low sample consumption of less than 10 µL, cost-effectiveness, and eco-friendliness such as reduced solvent use and lower operational costs. However, CE also faces limitations, including limited detection sensitivity for low-concentration samples and interference from complex biological matrices. Prior to performing CE, it is common to utilize sample preparation procedures such as solid-phase microextraction (SPME) and liquid-phase microextraction (LPME) in order to improve the sensitivity and selectivity of the analysis. Recently, there have been advancements in the development of novel materials that have the potential to greatly enhance the performance of SPME and LPME. This review examines various materials and their uses in microextraction when combined with CE. These materials include carbon nanotubes, covalent organic frameworks, metal-organic frameworks, graphene and its derivatives, molecularly imprinted polymers, layered double hydroxides, ionic liquids, and deep eutectic solvents. The utilization of these innovative materials in extraction methods is being examined. Analyte recoveries and detection limits attained for a range of sample matrices are used to assess their effects on extraction selectivity, sensitivity, and efficiency. Exploring new materials for use in sample preparation techniques is important as it enables researchers to address current limitations of CE. The development of novel materials has the potential to greatly enhance extraction selectivity, sensitivity, and efficiency, thereby improving CE performance for complex biological analysis.

Reversible Hydrophobic Deep Eutectic Solvent-Based Uranyl-Sensing Optode Film in Aqueous Streams: Color Transformation and Reusability

A hydrophobic deep eutectic solvent (HDES)-based optode was designed for the preconcentration and determination of the UO22+ ion in aqueous media using spectroscopic techniques [energy-dispersive X-ray fluorescence (EDXRF) and solid-state absorption]. The optode was developed by incorporation of HDES (tri-n-octyl phosphine oxide and decanoic acid in an equimolar ratio), tri-(2-ethylhexyl) phosphate, and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol into a cellulose triacetate matrix. Characterization studies were carried out using different techniques to understand the roles of HDES as a plasticizer, UO22+ extractant, and Br-PADAP immobilizer. Uptake studies revealed that the optimal pH was 3 and sorption followed the type II adsorption isotherm. Uranium in the U-sorbed optode can be directly analyzed over a large concentration range of 0.021 × 10-3-2.1 × 10-3 Mol L-1 using EDXRF. The optode film exhibited a linear dynamic range of 0.84 × 10-6-84 × 10-6 Mol L-1 for uranium, with a lowest limit of detection of 0.084 × 10-6 Mol L-1 by colorimetric analysis. This optode-based method was employed for seawater analysis for its UO22+ concentration without any matrix separation, and the concentration was found to be 1.30 ± 0.06 × 10-8 Mol L-1. The optode exhibited better selectivity for UO22+ in the presence of various cations including Sr2+ and Cs+ in an aqueous medium. Compared to other prevailing optical sensors, this optode performed better in terms of key factors like pH, equilibration time, reusability, and detection limit.

Recent advances and challenges in the analysis of natural toxins

Natural toxins (NTs) are poisonous secondary metabolites produced by living organisms developed to ward off predators. Especially low molecular weight NTs (MW<∼1 kDa), such as mycotoxins, phycotoxins, and plant toxins, are considered an important and growing food safety concern. Therefore, accurate risk assessment of food and feed for the presence of NTs is crucial. Currently, the analysis of NTs is predominantly performed with targeted high pressure liquid chromatography tandem mass spectrometry (HPLC-MS/MS) methods. Although these methods are highly sensitive and accurate, they are relatively expensive and time-consuming, while unknown or unexpected NTs will be missed. To overcome this, novel on-site screening methods and non-targeted HPLC high resolution mass spectrometry (HRMS) methods have been developed. On-site screening methods can give non-specialists the possibility for broad "scanning" of potential geographical regions of interest, while also providing sensitive and specific analysis at the point-of-need. Non-targeted chromatography-HRMS methods can detect unexpected as well as unknown NTs and their metabolites in a lab-based approach. The aim of this chapter is to provide an insight in the recent advances, challenges, and perspectives in the field of NTs analysis both from the on-site and the laboratory perspective.

Translational and reorientational dynamics in carboxylic acid-based deep eutectic solvents

The glass formation and the dipolar reorientational motions in deep eutectic solvents (DESs) are frequently overlooked, despite their crucial role in defining the room-temperature physiochemical properties. To understand the effects of these dynamics on the ionic conductivity and their relation to the mechanical properties of the DES, we conducted broadband dielectric and rheological spectroscopy over a wide temperature range on three well-established carboxylic acid-based natural DESs. These are the eutectic mixtures of choline chloride with oxalic acid (oxaline), malonic acid (maline), and phenylacetic acid (phenylaceline). In all three DESs, we observe signs of a glass transition in the temperature dependence of their dipolar reorientational and structural dynamics, as well as varying degrees of motional decoupling between the different observed dynamics. Maline and oxaline display a breaking of the Walden rule near the glass-transition temperature, while the relation between the dc conductivity and dipolar relaxation time in both maline and phenylaceline is best described by a power law. The glass-forming properties of the investigated systems not only govern the orientational dipolar motions and rheological properties, which are of interest from a fundamental point of view, but they also affect the dc conductivity, even at room temperature, which is of high technical relevance.

Stereoselective separation of psychoactive substances: Multivariate optimization and validation of a capillary electrophoresis method using carboxymethyl-β-CD/deep eutectic solvent dual system

A comprehensive study was performed to determine an optimum enantioseparation method for fluorine-substituted amphetamine and cathinone derivatives (fluor-amphetamine and fluor-cathinone derivatives), using a binary system consisting of carboxymethyl-β-CD (CM-β-CD) and a deep eutectic solvent (DES), namely choline chloride-ethylene glycol (ChCl-EG). Under this framework, the optimization and modeling of the separation conditions in a binary system were performed with the objective of maximizing resolution and minimizing analysis time. This was achieved through the application of response surface methodology. In particular, the effect of chiral selector concentration and percentage of DES on resolution and analysis time were investigated and optimized using a complete experimental design. The optimum enantioseparation conditions were determined to be 13.84 mM CM-β-CD and 0.15% v/v ChCl-EG for fluorine-substituted amphetamine derivatives and 14.36 mM and 0.75% v/v ChCl-EG for fluorine-substituted cathinone derivatives, respectively. This combination resulted in a baseline separation for eight out of the nine analytes studied. Overall, the results demonstrated the synergistic effect of the CM-β-CD/DES dual system and highlighted the significance of DESs as additives in capillary electrophoresis.

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.

Deep eutectic solvents based in situ isolation technique for extractive deterpenation of essential oils

Essential oils, intricate blends of volatile compounds obtained from a variety of sources, play a crucial role in numerous industries. To elevate product quality, deterpenation becomes an indispensable step. This study proposes an in situ isolation technique based on deep eutectic solvents (DESs) for the deterpenation of essential oil. Salient features of relevant compounds were obtained using conductor-like screening model for real solvents (COSMO-RS) and density functional theory (DFT) methods to predict deterpenation performance. Tetrabutylammonium chloride (TBAC) was chosen based on the results of theoretical analysis and experiment to extract hydroxy-terpenoids. COSMO-RS was employed to evaluate the extraction performance at different molar ratios, and then combined with experimental analysis to determine the optimal conditions. The σ-profiles of organic solvents and their interactions with terpene revealed n-hexane to be the best solvent for purifying DES. TBAC and terpenoids were obtained through the re-extraction procedure, with a recovery of 81.8-84.4%.

Green Deep Eutectic Solvents (DESs) for Sustainable Metal Recovery from Thermally Treated PCBs: A Greener Alternative to Conventional Methods

Waste PCBs the core of e-waste is rich in copper, tin, zinc, iron, and nickel. Leaching base metals from PCB used to be done in toxic, corrosive acidic/alkali mediums. In this work, an environmentally friendly method for leaching metals from thermally treated PCBs (TPCBs) of mobile phones was proposed using choline chloride based deep eutectic solvents (DES). DES selectivity and solubility of metals from metal oxides were the main screening criteria. FA-ChCl had the maximum solubility of Cu, Fe, and Ni, while Urea-ChCl had high Zn selectivity and solubility. Oxalic acid has high selectivity for Sn. FA-ChCl extracted Cu and Fe best at 16 h, 100 °C, and 1/30 g/mL. Urea-ChCl extracted Zn (90.4±2.9 %) from TPCBs at 100 °C, 21 h, 1/20 g/mL, and 400 rpm. Oxalic acid (1 M) removed 92.3±2.1 % Sn from TPCBs in 1 h at 80 °C and 1/20 g/mL. The shrinking core model-based kinetic investigation of FA-ChCl for Cu extraction showed a diffusion-controlled process. The proposed method is greener than mineral acids utilized for metal extraction.

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.

Microstructural Evolution of Zinc-Ion Species from Aqueous to Hydrated Eutectic Electrolyte for Zn-Ion Batteries

Despite their intrinsic safety and environmental friendliness, typical aqueous Zn-ion rechargeable batteries have been struggling with poor reversibility and electrochemical stability. Hydrated eutectic electrolytes (HEEs) have been attracting extensive attention due to their appealing features of high designability and superior performances over typical aqueous electrolytes. However, an in-depth understanding of unique microstructure in HEEs and the ensuing superior performances remains obscure, limiting the development of enhanced electrolytes. Herein, we demonstrate a distinct evolution path of Zn-ion species from aqueous to superior hydrated eutectic electrolytes, which experience a special transition state enriched with H-bonds between eutectic molecules. Complementary with the well-studied reorganized solvation structure induced by short-ranged salt-solvent interaction, long-range solvent-solvent interactions arising from the H-bond reorganizes the extended electrolyte microstructure, which in turn influences the cation diffusion mechanisms and interfacial reaction kinetics. Overall, we highlight the importance of ion species microstructural evolution in the rational design of superior aqueous electrolytes.

Biobased natural deep eutectic system as versatile solvents: Structure, interaction and advanced applications

The increasing emphasis on the development of green replacements to traditional organic solvents and ionic liquids (ILs) can be attributed to the rising concerns over human health and detrimental impacts of conventional solvents towards the environment. A new generation of solvents inspired by nature and extracted from plant bioresources has evolved over the last few years, and are referred to as natural deep eutectic solvents (NADES). NADES are mixtures of natural constituents like sugars, polyalcohols, sugar-based alcohols, amino acids and organic acids. Interest in NADES has exponentially grown over the last eight years, which is evident from an upsurge in the number of research projects undertaken. NADES are highly biocompatible as they can be biosynthesized and metabolized by nearly all living organisms. These solvents pose several noteworthy advantages, such as easy synthesis, tuneable physico-chemical properties, low toxicity, high biodegradability, solute sustainability and stabilization and low melting point. Research on the applicability of NADES in diverse areas is gaining momentum, which includes as - media for chemical and enzymatic reactions; extraction media for essential oils; anti-inflammatory and antimicrobial agent; extraction of bioactive composites; as chromatographic media; preservatives for labile compounds and in drug synthesis. This review gives a complete overview of the properties, biodegradability and toxicity of NADES which we propose can assist in further knowledge generation on their significance in biological systems and usage in green and sustainable chemistry. Information on applications of NADES in biomedical, therapeutic and pharma-biotechnology fields is also highlighted in the current article along with the recent progress and future perspectives in novel applications of NADES.

Uncovering the Critical Factors that Enable Extractive Desulfurization of Fuels in Ionic Liquids and Deep Eutectic Solvents from Simulations

Environmental regulatory agencies have implemented stringent restrictions on the permissible levels of sulfur compounds in fuel to reduce harmful emissions and improve air quality. Problematically, traditional desulfurization methods have shown low effectiveness in the removal of refractory sulfur compounds, e.g., thiophene (TS), dibenzothiophene (DBT), and 4-methyldibenzothiophene (MDBT). In this work, molecular dynamics (MD) simulations and free energy perturbation (FEP) have been applied to investigate the use of ionic liquids (ILs) and deep eutectic solvents (DESs) as efficient TS/DBT/MDBT extractants. For the IL simulations, the selected cation was 1-butyl-3-methylimidazolium [BMIM] and the anions included chloride [Cl], thiocyanate [SCN], tetrafluoroborate [BF₄], hexafluorophosphate [PF₆], and bis(trifluoromethylsulfonyl)amide [NTf₂]. The DESs were composed of choline chloride with ethylene glycol (CCEtg) or with glycerol (CCGly). Calculation of excess chemical potentials predicted the ILs to be more promising extractants with energies lower by 1-3 kcal/mol compared to DESs. Increasing IL anion size was positively correlated to enhanced solvation of S-compounds, which was influenced by energetically dominant solute-anion interactions and favorable solute-[BMIM] π-π stacking. For the DESs, the solvent components offered a range of synergistic, yet comparatively weaker, electrostatic interactions that included hydrogen bonding and cation-π interactions. An in-depth analysis of the structure of IL and DES systems is presented, along with a discussion of the critical factors behind experimental trends of S-compound extraction efficiency.

Menthol-based deep eutectic systems as antimicrobial and anti-inflammatory agents for wound healing

Effective antimicrobial treatment has been identified as a serious and unmet medical need. Herein, we present a strategy based on deep eutectic systems (DES) to overcome current limitations, answering the need not only to effectively kill bacterial agents but also to avoid their adhesion and proliferation, which is associated with biofilm formation and have a crucial impact on bacterial virulence. To achieve such a goal, natural deep eutectic systems (NADES) based on menthol (Me) and saturated free fatty acids (FFA) were produced, fully physicochemical characterized, and its bioactive properties were described. The antimicrobial potential of menthol-based NADES with FFA, namely, myristic acid (MA), lauric acid (LA), and stearic acid (SA) were investigated towards a broad panel of microorganisms. The obtained data indicates that NADES possess effective antimicrobial properties towards the Gram-positive bacterial and fungal strains tested. Among the tested formulations, Me:LA at a molar ratio of 4:1 molar was used to carry out a biofilm detachment/removal assay due to is superior microbiological properties. This formulation was able to effectively lead to biofilm removal/dispersion of not only methicillin-resistant Staphylococcus aureus (MRSA) and Candida albicans, but also Escherichia coli, without the need of any additional physical force or antibiotic. Furthermore, since microbial invasion and biofilm formation is highly undesired in wound healing, namely in chronic wound healing, the wound healing properties of these eutectic formulations was also investigated. The results suggest that these NADES can cope with microbial invasion and biofilm detachment while not compromising normal keratinocyte proliferation and migration verified in wound healing and epidermis repair, while also contributing to the reduction of cell stress and inflammation via the control of ROS production. In conclusion, these results provide the indication that NADES based on Me and FFA holds great interest as antimicrobial agents for preventive and therapeutic applications in various clinical settings, including wound healing.

Juçara Fruit (Euterpe Edulis Martius) Valorization Combining Emergent Extraction Technologies and Aqueous Solutions of Alkanediols

Anthocyanins from juçara fruits were extracted by pressurized liquid extraction (PLE) or ultrasound-assisted extraction (UAE), using aqueous solutions of 1,2-alkanediols and glycerol ethers as biobased solvents. The PLE (100 bar, 13 min, 1 mL/min flow rate) in the optimal extraction conditions originated 23.1 mg_anthocyanins·g_{dry biomass}^-1. On the other hand, the UAE was 10 min long, and the optimal conditions using 1,2-propanediol were 42.6 wt%, 160 W, and pH 7.0, leading to 50 mg_anthocyanins·g_{dry biomass}^-1. Extractions at the UAE optimized conditions, with aqueous solutions of five different 1,2-alkanediols and three glycerol ethers were performed, and compared to water and ethanolic extracts. The biobased solvent solutions presented anthocyanin yields up to 33% higher than water, and were shown to be as efficient as ethanol/water, but generated extracts with higher antioxidant capacity. The anthocyanin-rich extract of juçara, obtained with 1,2-propanediol, was used in the production of a natural soap and incorporated into a cream, showing that the addition of the juçara extract resulted in an antioxidant capacity in both products.

Insight into the Molecular Structure, Interaction, and Dynamics of Aqueous Reline Deep Eutectic Solvent: A Nuclear Magnetic Resonance Investigation

Reline, which is composed of choline chloride (ChCl) and urea, is the first and most widely used deep eutectic solvent (DES) described by Abbot and co-workers. Due to the hygroscopic feature, traces of water are unavoidable, which significantly affect the physicochemical properties of reline. At present, the local structure of molecules and the impact from the presence of water are still the most significant questions in this field. Herein, reline and six aqueous dilutions with a controlled amount of water (from 3.2 to 50.0 wt %) were studied mainly by using a combination of nuclear magnetic resonance (NMR) techniques. According to 1D ³⁵Cl NMR, 1D ¹⁵N NMR, and 2D ¹H-¹⁵Cl heteronuclear Overhauser effect spectroscopy, we probed the interactions of urea···Cl^- and Ch⁺···Cl^- in pure reline, which gradually dissociated in the presence of water. Moreover, it was revealed that the dissociation rate altered when the water content reached 9.0 wt %, which is ascribed to the higher preference of hydration for Cl^- ion compared to other species in the system. Furthermore, selected cross peaks in ¹H-¹H correlation spectroscopy spectra were analyzed. Accordingly, an enhanced correlation was observed for urea···Ch⁺ at a lower water fraction within 9.0 wt %. When the water content increased to 24.9 wt %, the water solvation of Ch⁺ and urea was also observed in COSY spectra. The interaction of H₂O···Ch⁺ got continuously stronger when the water content increased from 24.9 to 50.0 wt %, while H₂O···urea got enhanced when the water content reached 33.3 wt % and then diminished gradually from 33.3 to 50.0 wt %. ¹H-¹H nuclear Overhauser effect spectroscopy and ¹H-¹H rotating frame Overhauser effect spectroscopy experiments were also conducted for dynamics investigation. The τ_c value for the species in 9.0 wt % aqueous reline is very close to τ_c^crit of 0.44 ns. For pure reline and the aqueous reline with a water fraction of less than 9.0 wt %, the τ_c value of the species is longer than 0.44 ns, while for the sample with water of 24.9 wt %, the τ_c value is much shorter than 0.44 ns. Based on our NMR study, we revealed that with the water amount increasing from 0 to 50.0 wt %, the species involved in the system behaved as the large molecules or molecules in viscous liquids transiting to the medium-sized molecules in nonviscous liquids and finally to small molecules in nonviscous liquids.

Up/Down Tuning of Poly(ionic liquid)s in Aqueous Two-Phase Systems

Thermally induced reversible up/down migration of poly(ionic liquid)s (PILs) in aqueous two-phase systems (ATPSs) was achieved for the first time in this study. Novel ATPSs were fabricated using azobenzene (Azo)- and benzyl (Bn)-modified PILs, and their upper and lower phases could be easily tuned using the grafting degree (GD) of the Azo and Bn groups. Bn-PIL with higher GD_Bn could go up into the upper phase and Azo-PIL come down to the lower phase when the temperature increased (>65 °C); this behavior was reversed at lower temperatures. Moreover, a reversible two-phase/single-phase transition was realized under UV irradiation. Experimental and simulation results revealed that the difference in the hydration capacity between Bn-PIL and Azo-PIL accounted for their unique phase-separation behavior. A versatile platform for fabricating ATPSs with tunable stimuli-responsive behavior can be realized based on our findings, which can broaden their applications in the fields of smart separation systems and functional material development.

Natural Deep Eutectic Solvents (NADESs) Combined with Sustainable Extraction Techniques: A Review of the Green Chemistry Approach in Food Analysis

Usual extraction processes for analyzing foods, supplements, and nutraceutical products involve massive amounts of organic solvents contributing to a negative impact on the environment and human health. In recent years, a new class of green solvents called natural deep eutectic solvents (NADES) have been considered a valid alternative to conventional solvents. Compared with conventional organic solvents, NADES have attracted considerable attention since they are sustainable, biodegradable, and non-toxic but also are easy to prepare, and have low production costs. Here we summarize the major aspects of NADEs such as the classification, preparation method physicochemical properties, and toxicity. Moreover, we provide an overview of novel extraction techniques using NADES as potential extractants of bioactive compounds from foods and food by-products, and application of NADEs in food analysis. This review aims to be useful for the further development of NAES and for broadening the knowledge of these new green solvents in order to increase their use for the extraction of bioactive compounds and in food analysis.

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

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

An Overview of the Application of Harmony Search for Chemical Engineering Optimization

Harmony search algorithm and its variants have been used in several applications in medicine, telecommunications, computer science, and engineering. This article reviews the global and multi-objective optimization for chemical engineering using harmony search. The main features of the HS method and several of its popular variants and hybrid versions including their relevant algorithm characteristics are described and discussed. A variety of global and multi-objective optimization problems from chemical engineering and their resolution using HS-based methods are also included. These problems involve thermodynamic calculations (phase stability analysis, phase equilibrium calculations, parameter estimation, and azeotrope calculation), heat exchanger design, distillation simulation, life cycle analysis, and water distribution systems, among others. Remarks on future developments of HS and its related algorithms for global and multi-objective optimization in chemical engineering are also provided in this review. HS is a reliable and promising stochastic optimizer to resolve challenging global and multi-objective optimization problems for process systems engineering.

Natural Deep Eutectic Solvent-Based Dispersive Liquid-Liquid Microextraction Coupled with Direct Analysis in Real Time Mass Spectrometry: A Green Temperature-Mediated Analytical Strategy

Green analytical chemistry (GAC) represents a rapidly growing research field that aims at developing novel analytical approaches with minimal consumption of hazardous reagents and solvents. The current study reports on a GAC methodology exploiting the unique physicochemical properties of natural deep eutectic solvents (NADESs), a supposedly environmentally friendly class of solvents. Based on a temperature-mediated strategy, the NADESs were manipulated to undergo multiple phase transitions for favorable functionality and performance. As proof-of-concept demonstrations, both hydrophobic and hydrophilic NADESs were prepared for the extraction and analysis of eight phthalate esters in aqueous samples (food simulants) and three aflatoxins in oily samples (edible oils), respectively. NADES-based dispersive liquid-liquid microextraction (DLLME) was employed to achieve high-efficiency sample pretreatment. Afterward, the NADESs were transformed from liquids into solids by tuning the peripheral temperature for a convenient phase separation from the sample matrices. The solidified NADES extracts were melted and vaporized at elevated temperatures by transmission-mode direct analysis in real time (DART) for further quadrupole-Orbitrap high-resolution mass spectrometry (Q-Orbitrap HRMS) analysis. The developed protocol was validated, achieving good repeatability with relative standard deviations (RSDs) of less than 9% and satisfactory sensitivity with limits of detection (LODs) and quantitation (LOQs) ranging from 0.1 to 0.8 and 0.2 to 2.0 μg/kg, respectively. The greenness of the analytical methodology was assessed with the calculated scores of 0.66 and 0.57 for the hydrophobic and hydrophilic NADES-based protocols, respectively. The method was applied to marketed samples, highlighting the great potential for green chemical analysis.

Organic waste recycling for carbon smart circular bioeconomy and sustainable development: A review

The development of sustainable and low carbon impact processes for a suitable management of waste and by-products coming from different factors of the industrial value chain like agricultural, forestry and food processing industries. Implementing this will helps to avoid the negative environmental impact and global warming. The application of the circular bioeconomy (CB) and the circular economic models have been shown to be a great opportunity for facing the waste and by-products issues by bringing sustainable processing systems which allow to the value chains be more responsible and resilient. In addition, biorefinery approach coupled to CB context could offer different solution and insights to conquer the current challenges related to decrease the fossil fuel dependency as well as increase efficiency of resource recovery and processing cost of the industrial residues. It is worth to remark the important role that the biotechnological processes such as fermentative, digestive and enzymatic conversions play for an effective waste management and carbon neutrality.

Effective Absorption Mechanism of SO2 and NO2 in the Flue Gas by Ammonium-Bromide-Based Deep Eutectic Solvents

Simultaneous capture of SO₂ and NO _x from flue gas is critical for coal-fired power generation. In this study, environmentally friendly and high-performance deep eutectic solvents based on ethylene glycol and ammonium bromide were designed to capture SO₂ and NO₂ simultaneously. The SO₂ and NO₂ absorption performances and absorption mechanisms were systematically investigated by ¹H NMR and Fourier transform infrared (FT-IR) spectroscopy in combination with ab initio calculations using Gaussian software. The results showed that EG-TBAB DESs can absorb low concentrations of SO₂ and NO₂ from the flue gas simultaneously at low temperatures (≤50 °C). ¹H NMR, FT-IR, and simulation results indicate that SO₂ and NO₂ are absorbed by forming EG-TBAB-SO₂-NO₂ complexes, Br^- is the main active site for NO₂ absorption, and NO₂ is more active in an EG-TBAB-NO₂-SO₂ complex than SO₂. EG-TBAB DESs exhibit outstanding regeneration capability, and absorption capacities remain unchanged after five absorption-desorption cycles. The fundamental understanding of simultaneous capture of SO₂ and NO₂ from this study enables DES structures to be rationally designed for efficient and low-cost desulfurization and denitrification reagents.

Ionic-Liquid-Based Aqueous Two-Phase Systems Induced by Intra- and Intermolecular Hydrogen Bonds

In recent years, aqueous two-phase systems (ATPSs) have been widely used in different fields and have become an increasingly attractive subject due to their application in the separation and purification of biomolecules. In this work, the aqueous phase behavior of ionic liquids (ILs) was modulated by changing the cis-trans structure of the anion in ILs. With the same tetra-butyl-phosphine as the cation, the cis-anion exhibited upper critical solution temperature (UCST) phenomena. In contrast, the trans-anion exhibited lower critical solution temperature (LCST) phenomena. The proposed mechanism shows that the main factors responsible for these phenomena include variations in the dissociation degree with temperature and the steric hindrance of the ILs. This phase behavior combines the chemical equilibrium in a solution with the microstructure of the molecule and is useful for constructing new chemical dynamic equilibria in ATPS. As an example of its application, aqueous solutions of both ILs can be used for the efficient separation and extraction of specific amino acids. The two ATPS systems reported in this work highlight a simple, effective, and environmentally friendly method for separating small biological molecules.

Advances of Ionic Liquids and Deep Eutectic Solvents in Green Processes of Biomass-Derived 5-Hydroxymethylfurfural

5-Hydroxymethylfurfural (HMF) is identified as an important bio-based platform chemical to bridge petroleum-based and biomass-based resources. It can be obtained through dehydration of various carbohydrates as well as converted to value-added fuels and chemicals. As designer solvents, ionic liquids (ILs) and deep eutectic solvents (DESs) have been widely used in catalytic transformation of biomass derivatives to various chemicals. This Review summarizes recent progress in experimental and theoretical studies on dehydration of carbohydrates such as fructose, glucose, sucrose, cellobiose, chitosan, cellulose, inulin, and even raw biomass to generate HMF using ILs and DESs as catalysts/cocatalysts and/or solvents/cosolvents. It also gives an overview of IL and DES-involved catalytic transformation of HMF to downstream products via oxidation, reduction, esterification, decarboxylation, and so forth. Challenges and prospects of ILs and DESs are also proposed for further production of HMF and HMF derivatives from biomass in green and sustainable processes.

Rationally Designed Ternary Deep Eutectic Solvent Enabling Higher Performance for Non-Aqueous Redox Flow Batteries

Redox flow batteries hold promise as large-scale energy storage systems for off-grid electrification. The electrolyte is one of the key components of redox batteries. Inspired by the mechanism involved in solvents for extraction, a ternary deep eutectic solvent (DES) is demonstrated, in which glycerol is introduced into the original binary ethaline DES. Redox pairs (active substance) dissolved in the solvent have low charge transfer resistance. The results show that the viscosity of the solvent with the ratio of choline chloride to ethylene glycol to glycerol of 1:2:0.5 decreases from 51.2 mPa·s to 40.3 mPa·s after adding the redox pair, implying that the mass transfer resistance of redox pairs in this solvent is reduced. Subsequent cyclic voltammetry and impedance tests show that the electrochemical performance with the ternary DES as the electrolyte in redox flow batteries is improved. When the ratio of 1:2:0.5 ternary DES is used as the electrolyte, the power density of the battery (9.01 mW·cm−2) is 38.2% higher than that of the binary one (6.52 mW·cm−2). Fourier transform infrared spectroscopy further indicates that the introduction of glycerol breaks the hydrogen bond network of the solvent environment where the redox pair is located, unraveling the hydrogen bond supramolecular complex. Rational solvent design is an effective strategy to enhance the electrochemical performance of redox batteries.

Revisiting the Physicochemical Properties and Applications of Deep Eutectic Solvents

Recently, deep eutectic solvent (DES) or ionic liquid (IL) analogues have been considered as the newest green solvent, demonstrating the potential to replace harsh volatile organic solvents. DESs are mainly a combination of two compounds: hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD), which have the ability to interact through extensive hydrogen bonds. A thorough understanding of their physicochemical properties is essential, given their successful applications on an industrial scale. The appropriate blend of HBA to HBD can easily fine-tune DES properties for desired applications. In this context, we have reviewed the basic information related to DESs, the two most studied physicochemical properties (density and viscosity), and their performance as a solvent in (i) drug delivery and (ii) extraction of biomolecules. A broader approach of various factors affecting their performance has been considered, giving a detailed picture of the current status of DESs in research and development.

Hydrophobic deep eutectic solvents as green absorbents for hydrophilic VOC elimination

As a common hydrophilic volatile organic compound (VOC), acetone is known to harm human health and the atmospheric environment. Absorption is a typical technique applied to capture hydrophilic VOCs; however, the difficulty of separating and recovering absorbed hydrophilic VOCs (e.g., acetone) from aqueous absorbents has become one of the major challenges in practical applications. Hydrophobic deep eutectic solvents (DESs) have therefore been developed as novel green absorbents for capturing hydrophilic VOCs in the present work. The compiled results show that efficient hydrophilic VOC elimination can be accomplished by the proposed hydrophobic DESs through high absorption capacity and thermodynamically favorable gas-to-liquid mass transfer. Among the explored DESs, the hydrophobic DES containing thymol [Thy] and decanoic acid [DecA] with a molar ratio of 1:1 has achieved the highest absorption capacity of acetone, i.e., 6.57 mg acetone per g DES at 20 °C and 1480 ppm acetone. The oxygen of acetone interacts favorably with the hydrogen atom of [Thy] upon absorption, rendering hydrogen bonding interaction surpassing polarity as the key factor in attaining superior solubility of acetone in DESs. Moreover, the absorbed acetone can be easily removed from Thy-based DESs, realizing an effective hydrophilic VOC elimination process with economic and ecological benefits.

Deep Eutectic Solvents in Solar Energy Technologies

Deep Eutectic Solvents (DESs) have been widely used in many fields to exploit their ecofriendly characteristics, from green synthetic procedures to environmentally benign industrial methods. In contrast, their application in emerging solar technologies, where the abundant and clean solar energy is used to properly respond to most important societal needs, is still relatively scarce. This represents a strong limitation since many solar devices make use of polluting or toxic components, thus seriously hampering their eco-friendly nature. Herein, we review the literature, mainly published in the last few years, on the use of DESs in representative solar technologies, from solar plants to last generation photovoltaics, featuring not only their passive role as green solvents, but also their active behavior arising from their peculiar chemical nature. This collection highlights the increasing and valuable role played by DESs in solar technologies, in the fulfillment of green chemistry requirements and for performance enhancement, in particular in terms of long-term temporal stability.

Extraction of Polyphenols from Olive Leaves Employing Deep Eutectic Solvents: The Application of Chemometrics to a Quantitative Study on Antioxidant Compounds

The extraction of phenolic compounds from olive leaves was optimized using three glycerol-based deep eutectic solvents (DESs) with lysine, proline, and arginine. A three-level Box–Behnken design was used to examine the influence of the liquid/solid ratio, concentration of DESs, and extraction temperature on the yield of the extraction process. A second-order polynomial model was used for predicting the polyphenol extraction yield. The optimal predicted conditions were used for extractions and they provided the highest total phenol yields with the glycerol–lysine exhibiting the best performance. Quantification of tyrosol, hydroxytyrosol, oleuropein, luteolin-7-O-glucoside, and rutin in the extracts showed high content in tyrosol in all DESs, particularly with glycerol–lysine and relatively similar contents with other studies for the other phenolic compounds. Finally, a linear relationship between tyrosol content and the total phenolic content of the extracts was observed.

Deep Eutectic Solvents as Active Pharmaceutical Ingredient Delivery Systems in the Treatment of Metabolic Related Diseases

Metabolic related diseases such as cancer, diabetes mellitus and atherosclerosis are major challenges for human health and safety worldwide due to their associations with high morbidity and mortality. It is of great significance to develop the effective active pharmaceutical ingredient (API) delivery systems for treatment of metabolic diseases. With their unique merits like easy preparation, high adjustability, low toxicity, low cost, satisfactory stability and biodegradation, deep eutectic solvents (DESs) are unarguably green and sustainable API delivery systems that have been developed to improve drug solubility and treat metabolic related diseases including cancer, diabetes mellitus and atherosclerosis. Many reports about DESs as API delivery systems in the therapy of cancer, diabetes mellitus and atherosclerosis exist but no systematic overview of these results is available, which motivated the current work.

Successive preconcentration and mechanistic investigation of Au(iii), Pd(ii), Pt(iv) and Rh(iii) via cloud point extraction using a functionalised ionic liquid

This study proposes the efficient separation of Au(iii)/Pd(ii)/Pt(iv)/Rh(iii) through the 2-mercaptobenzothiazole-functionalised ionic liquid ([C6mim][2MBT]) using a cloud point extraction system.

Eutectic-based liposome as a potential delivery system of paeonol

Deep eutectic solvents (DESs), as a new type of green solvent, show great advantages of easy preparation and no need of purification after synthesis and have great potential applications in various fields. Moreover, when combining active pharmaceutical ingredients (APIs) with DESs, a new type of drug delivery system called a therapeutic deep eutectic solvent (THEDES) can be developed to increase the solubility of the APIs and/or their permeation ability as well as bioactivity. Herein, we have designed a new THEDES based on paeonol and lauric acid with a molar ratio of 1 : 1. The physicochemical properties as well as the bioactivity were investigated by a series of techniques. The THEDES showed better solubility in water and similar bioactivities as compared to the pure APIs. Besides, we further prepared a THEDES liposome, which possessed an average size of about 120 nm with an encapsulation efficiency of 84%. The obtained liposome showed good stability during the experimental period, which indicated a potential application for the delivery of paeonol. The results presented herein suggested that THEDES may be regarded as a new strategy for the effective delivery of APIs.