Project description:As functional liquid media, natural deep eutectic solvent (NADES) species can dissolve natural or synthetic chemicals of low water solubility. Moreover, the special properties of NADES, such as biodegradability and biocompatibility, suggest that they are alternative candidates for concepts and applications involving some organic solvents and ionic liquids. Owing to the growing comprehension of the eutectic mechanisms and the advancing interest in the natural eutectic phenomenon, many NADES applications have been developed in the past several years. However, unlike organic solvents, the basic structural unit of NADES media primarily depends on the intermolecular interactions among their components. This makes NADES matrices readily influenced by various factors, such as water content, temperature, and component ratio and, thus, extends the metabolomic challenge of natural products (NPs). To enhance the understanding of the importance of NADES in biological systems, this review focuses on NADES properties and applications in NP research. The present thorough chronological and statistical analysis of existing report adds to the recognition of the distinctiveness of (NA)DES, involves a discussion of NADES-related observations in NP research, and reportes applications of these eutectic mixtures. The work identifies potential areas for future studies of (NA)DES by evaluating relevant applications, including their use as extraction and chromatographic media as well as their biomedical relevance. The chemical diversity of natural metabolites that generate or participate in NADES formation highlights the growing insight that biosynthetically primordial metabolites (PRIMs) are as essential to the biological function and bioactivity of unrefined natural products as the biosynthetically more highly evolutionary metabolites (HEVOs) that can be isolated from crude mixtures.
Project description:The solubility of CO2 in hydrophobic deep eutectic solvents (DESs) has been measured for the first time. Six different hydrophobic DESs are studied in the temperature range from 298 to 323 K and at CO2 pressures up to 2 MPa. The results are evaluated by comparing the solubility data with existing hydrophilic DESs and currently applied physical solvents and fluorinated ionic liquids. The DESs are prepared by mixing decanoic acid with a quaternary ammonium salt with different halide anions and alkyl chain lengths. The measured CO2 solubilities are similar to those found in renowned fluorinated ILs, while the heats of CO2 absorption are in the range of nonpolar solvents. The presented DESs show good potential to be used as CO2 capture agents.
Project description:Deep eutectic solvents (DESs) formed by hydrogen bond donors and acceptors are a promising new class of solvents. Both hydrophilic and hydrophobic binary DESs readily absorb water, making them ternary mixtures, and a small water content is always inevitable under ambient conditions. We present a thorough study of a typical hydrophobic DES formed by a 1:2 mole ratio of tetrabutyl ammonium chloride and decanoic acid, focusing on the effects of a low water content caused by absorbed water vapor, using multinuclear NMR techniques, molecular modeling, and several other physicochemical techniques. Already very low water contents cause dynamic nanoscale phase segregation, reduce solvent viscosity and fragility, increase self-diffusion coefficients and conductivity, and enhance local dynamics. Water interferes with the hydrogen-bonding network between the chloride ions and carboxylic acid groups by solvating them, which enhances carboxylic acid self-correlation and ion pair formation between tetrabutyl ammonium and chloride. Simulations show that the component molar ratio can be varied, with an effect on the internal structure. The water-induced changes in the physical properties are beneficial for most prospective applications but water creates an acidic aqueous nanophase with a high halide ion concentration, which may have chemically adverse effects.
Project description:Deep eutectic solvents (DESs) are a new class of solvents with wider potential window than that of water and high electrochemical stability, making them potential candidates for a wide range of electrochemical systems. However, due to the hygroscopic nature of DESs, the presence of latent water is unavoidable. Therefore, understanding the interfacial structure and the electrosorption and distribution of residual water at the electrified interface is of great importance for the use of these solvents in electrochemical systems. Using atomistic molecular dynamics, we explore the electrosorption and distribution of different amounts of water in 1 : 2 choline chloride-urea DES (Reline) at the electrified graphene interface. We found that both the water distribution and the interfacial structure are sensitive to the electrification of the graphene electrode. As a result, it is found that for moderately charged electrodes, water shows a preferential asymmetric adsorption in the vicinity of the positively charged electrode, partly due to strong intermolecular interactions with anions through hydrogen bonds. In contrast, for highly charged electrodes, water adsorbs at both electrodes due to a strongly enhanced external electrostatic interaction between the electrodes and the water dipoles.
Project description:This study outlines the methodology to model hydrophobic deep eutectic solvent (HDES) interactions to obtain computational results that accurately represent experimental results of furfural removal from water. Computational prediction with high accuracy of HDES behavior could elucidate hydrogen bond interaction in HDES. COSMOtherm modeling and experimental evaluation demonstrated that both decanoic and dodecanoic acid-based HDES can remove furfural from water even at very low concentrations of 0.1 mol %. The modeling methodology considered salts as independent cations, which were paired with the hydrogen bond donor (HBD) species. These resulted in computational predictions of liquid-liquid equilibrium (LLE) between tetra n-alkyl ammonium bromide salt-based HDES with >95% accuracy of experimental results. The COSMOtherm modeling methodology strengthens the understanding of HDES by considering intermolecular forces that affect electron density (σ) of the HDES components to determine the LLE of the HDES-aqueous system. This results in a deep eutectic phase that has a positive sigma potential (potentials, μ(σ), up to 0.1 kcal/mol Å2) at charge densities associated with hydrogen bonding (±0.0084 e/Å2). Though n-alkyl ammonium salts ranging from tetramethyl- to tetraoctylammonium bromide were considered in the computational model, only pentyl- and longer alkyl chains displayed hydrophobic behavior with less than 1% salt loss to the aqueous phase. However, there was still significant water uptake in the eutectic phase (final phase composition containing greater than 60 mol and 12% by mass) for the hydrophobic DES.
Project description:Triterpenic acids (TTAs), known for their promising biological properties, can be found in different biomass sources and related by-products, such as Eucalyptus globulus bark, and have been extracted using organic volatile solvents such as dichloromethane. Recently, deep eutectic solvents (DES) have been identified as promising alternatives for the extraction of value-added compounds from biomass. In the present work, several hydrophobic DES were tested for the extraction of TTAs from E. globulus bark. Initial solubility studies revealed that DES based on menthol and thymol as the most promising solvents for these compounds given the highest solubilities obtained for ursolic acid (UA) at temperatures ranging from room temperature up to 90 °C. Accordingly, an eutectic mixture of menthol:thymol (1:2) was confirmed as the best candidate for the TTAs extraction from E. globulus outer bark, leading to extraction yields (weight of TTA per weight of biomass) at room temperature of 1.8 wt% for ursolic acid, 0.84 wt% for oleanolic acid and 0.30 wt% for betulinic acid. These values are significantly higher than those obtained with conventional organic solvents under similar conditions. The results obtained using these DES are promising for the recovery of TTAs for nutraceutical and pharmacological applications, while reinforcing the potential of DES as promising solvents to be applied in biorefinery processes.
Project description: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.
Project description:Deep eutectic solvents (DESs) are eutectic mixtures of salts and hydrogen bond donors with melting points low enough to be used as solvents. DESs have proved to be a good alternative to traditional organic solvents and ionic liquids (ILs) in many biocatalytic processes. Apart from the benign characteristics similar to those of ILs (e.g., low volatility, low inflammability and low melting point), DESs have their unique merits of easy preparation and low cost owing to their renewable and available raw materials. To better apply such solvents in green and sustainable chemistry, this review firstly describes some basic properties, mainly the toxicity and biodegradability of DESs. Secondly, it presents several valuable applications of DES as solvent/co-solvent in biocatalytic reactions, such as lipase-catalyzed transesterification and ester hydrolysis reactions. The roles, serving as extractive reagent for an enzymatic product and pretreatment solvent of enzymatic biomass hydrolysis, are also discussed. Further understanding how DESs affect biocatalytic reaction will facilitate the design of novel solvents and contribute to the discovery of new reactions in these solvents.
Project description:The molecular weight of lignin extracted from lignocellulosic biomass is an important factor in determining its valorization in industrial processes. Herein, this work aims to explore the extraction of high molecular weight and bioactive lignin from water chestnut shells under mild conditions. Five kinds of deep eutectic solvents were prepared and applied to isolate lignin from water chestnut shells. The extracted lignin was further characterized with element analysis, gel permeation chromatography, and Ultraviolet-visible and Fourier-transform infrared spectroscopy. The distribution of pyrolysis products was identified and quantified with thermogravimetric analysis-Fourier-transform infrared spectroscopy and pyrolysis-gas chromatograph-mass spectrometry. The results showed that choline chloride/ethylene glycol/p-toluenesulfonic acid (1:1.8:0.2 molar ratio) exhibited the highest fractionation efficiency for lignin (84.17% yield) at 100 °C for 2 h. Simultaneously, the lignin showed high purity (90.4%), high relative molecular weight (37,077 g/mol), and excellent uniformity. Furthermore, the aromatic ring structure of lignin remained intact, consisting mainly of p-hydroxyphenyl, syringl, and guaiacyl subunits. The lignin generated a large number of volatile organic compounds during the depolymerization process, mainly composed of ketones, phenols, syringols, guaiacols, esters, and aromatic compounds. Finally, the antioxidant activity of the lignin sample was evaluated with the 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay; the lignin from water chestnut shells showed excellent antioxidant activity. These findings confirm that lignin from water chestnut shells has a broad application prospect in valuable chemicals, biofuels and bio-functional materials.