Choline Chloride-based Deep Eutectic Solvents Research Articles

Insights into the enhanced thermal stability of lysozyme with altered structure and activity induced by choline chloride-based deep eutectic solvents containing polyols and sugars

The stabilization of protein is crucial for its practical usage in industrial applications. This study sought to systematically determine how deep eutectic solvents (DESs) can stabilize proteins and affect their structure and activity by employing lysozyme as a model. Seven choline chloride (ChCl)-based DESs with polyols and sugars as hydrogen bond donors (HBDs) were evaluated as co-solvents at 10–75 wt% concentrations. The thermal stability (Tm) of lysozyme was improved by all DESs. The Tm increase had a positive correlation with the DES concentrations and the number of OH groups in HBDs. Increased α-helical contents in all conditions partially support the protein stabilization by DESs. Lysozyme could maintain its native tertiary structure and activity at 10 wt% DESs. At higher concentrations, the polyol-class DESs yielded higher Tm and more structure compaction with lower activity suppression than the sugar-class solvents, which displayed discernable changes in their tertiary structure with possible binding at the active site of lysozyme. The hydrogen-bonding ability of HBDs was suggested to play a key role in both classes of DESs by increasing the hydrogen bond network around the protein, which could recruit a protective hydration layer and lead to structure compaction.

Tailor-made deep eutectic solvents-based green extraction of natural antioxidants from partridge leaf-tea (Mallotus furetianus L.)

Herein, high efficient extraction of natural antioxidants from partridge leaf-tea (PLT) was carried out by using eco-friendly choline chloride-based deep eutectic solvents combined with ultrasonic method. Choline chloride-malic acid (ChCl-MaA), a new type of green solvent, with the highest efficient for extracting the natural antioxidants from PLT (DPPH-756.70 ± 12.13 μmol TE/g DW; FRAP-4139.17 ± 65.79 μM Fe(Ⅱ)SE/g DW) was screened for further optimization. The key parameters for simultaneously maximizing total phenolic content (TPC), total flavonoid content (TFC), 2,2-diphenyl-1-picrylhyldrazyl (DPPH) and ferric reducing antioxidant activity (FRAP) were optimized by single-factor experiments along with response surface methodology (RSM). Results exhibited that L/S ratio and water content in DES had significant effects on TPC and antioxidant activities, while ultrasonic power indicated a significant negative effect on all responses. Under the optimal conditions (ultrasonic power at 210 W, ultrasonic time at 30 min, L/S ratio at 27.50:1, water content in DES at 45%), experimentally obtained results were obtained as follows: 42.20 ± 2.17 mg GAE/g DW for TPC, 30.33 ± 2.16 mg RE/g DW for TFC, 838.64 ± 12.81 μmol TE/g DW for DPPH, and 5958.33 ± 153.52 μM Fe(Ⅱ)SE/g DW for FRAP, which were well in agreement with the predicted values. Furthermore, ChCl-MaA-based ultrasonic assisted extraction (UAE) yielded higher TPC, TFC and antioxidant activities compared with traditional solvents-based UAE. Strong antioxidant activities of PLT extracts were correlated with high levels of individual antioxidants including salvianic acid A, 3-chlorogenic acid, gallic acid, catechin and rutin. The functional groups analysis by Fourier transform infrared spectroscopy (FT-IR) were used to compare the solvents characterization before and after extraction. Scanning electron microscope (SEM) results further verified ChCl-MaA intensified the destruction of cell wall structure, and thereby allowed greater release of antioxidants from PLT. This work provides an eco-friendly ChCl-MaA-based UAE technique for efficiently extraction and valorization of phenolic compounds from PLT, which can be further used in pharmaceutical, food, and cosmetic industries.

Insights into alkaline choline chloride-based deep eutectic solvents pretreatment for Populus deltoides: Lignin structural features and modification mechanism

Deep eutectic solvent (DES) is a kind of green solvent for biorefinery, which favors the progress of being more environmentally friendly and effective. A better understanding of structural changes of lignin is necessary to optimize pretreatment conditions and efficient utilization of the resultant lignin. The current study reported the structural features of lignin recovered from alkaline ChCl/imidazole and ChCl/urea DES pretreatment, and the mechanism of lignin modification was revealed. The profiling demonstrated that lignin samples possessed a high purity (>94.4%), low molecular weight ranging from 1544 to 2562 g/mol and an excellent uniformity (PDI < 1.6). Noteworthy, the content of β-O-4′ linkages in lignin was over 75% (i.e. 72.2%–77.4% retention); S/G ratio was increased whereas the content of -OCH3 groups were decreased. It was revealed that slight cleavage of β-O-4′ linkages, preferential breakdown of G units, and demethylation reaction were occurred during alkaline ChCl-based DES pretreatment. Specifically, cleavage of ester linkages between PB and lignin macromolecule was taking place during ChCl/imidazole pretreatment at a high temperature; whereas oxidation only appeared in ChCl/urea system. Despite the modification, well β-O-4′ preserved and less condensed lignin samples were recovered after low-temperature pretreatment. Consequently, high contents of phenol derivatives (26.3–30.6%) were achieved in lignin oil. The present study provides critical information on alkaline ChCl-based DES pretreatment, which will contribute to the valorization of lignin by-products and will be beneficial to the development of biorefineries.

Tweaking Behavior of Hydrogen Bond Donor in Choline Chloride-Based Deep Eutectic Solvents for Regulating the Phase Transition of Poly(N-vinylcaprolactam): A Sustainable Medium for an Early Hydrophobic Collapse

Tweaking Behavior of Hydrogen Bond Donor in Choline Chloride-Based Deep Eutectic Solvents for Regulating the Phase Transition of Poly(<i>N</i>-vinylcaprolactam): A Sustainable Medium for an Early Hydrophobic Collapse

Separation of Aromatics from a Cyclic-Aliphatic Hydrocarbon Using Ethylene Glycol and a Choline Chloride-Based Deep Eutectic Solvent

Separation of Aromatics from a Cyclic-Aliphatic Hydrocarbon Using Ethylene Glycol and a Choline Chloride-Based Deep Eutectic Solvent

Evaluation of hybrid solvents featuring choline chloride-based deep eutectic solvents and ethanol as extractants for the liquid\u2013liquid extraction of benzene from n-hexane: towards a green and sustainable paradigm

Deep eutectic solvents (DESs) have high viscosities, but known to be mitigated by addition of suitable co-solvent. The effect of such co-solvent on the extraction efficiency of the hybrid solvent is hardly known. This study examined the effect of ethanol on three choline chloride-based DESs (glyceline, reline, and ethaline) by mixing each in turn with ethanol in various volume proportions. The hybrid solvents were evaluated for the extraction of benzene from n-hexane. Pseudo-ternary liquid–liquid equilibrium data were obtained using the refractive index method at 303 K and 1 atm for the systems, n-hexane (1) + benzene (2) + hybrid solvent (glyceline/ethanol, ethaline/ethanol, reline/ethanol) (3), and used to evaluate distribution coefficient (D) and selectivity (S). Furthermore, the physicochemical properties of the hybrid solvents were also determined. The results indicate increase in selectivity with increasing ethanol addition up to 50% and decrease with further addition. All hybrid solvents with 50% ethanol outperform sulfolane and are suitable replacement for same as green and sustainable extractant for aromatics from aliphatics. The glyceline + 50% ethanol emerged the overall best with 49.73% elevation in selectivity and 41.15% reduction in viscosity relative to the neat glyceline. The finding of this study is expected to fillip the drive for paradigm shift in petrochemical industries.

Investigating the Variation in Solvation Interactions of Choline Chloride-Based Deep Eutectic Solvents Formed Using Different Hydrogen Bond Donors

Investigating the Variation in Solvation Interactions of Choline Chloride-Based Deep Eutectic Solvents Formed Using Different Hydrogen Bond Donors

Evaluation of canonical choline chloride based deep eutectic solvents as dye-sensitized solar cell electrolytes.

Deep eutectic solvents (DESs) are beginning to attract interest as electrolyte alternatives to conventional organic solvents and ionic liquids within dye-sensitized solar cells (DSSCs). The precise roles played by DES components and whether they simply represent a benign medium for mobilizing charge carriers or present beneficial functionality that impacts device performance remain unclear. To begin to address this deficiency in understanding, we performed a comprehensive characterization of the three "canonical" choline chloride-based DESs (i.e., reline, ethaline, and glyceline) as DSSC electrolytes hosting the iodide-triiodide (I-/I3 -) redox couple. The measurement of electrolyte viscosities, determination of triiodide diffusion coefficients, and photovoltaic performances assessed for water contents up to 40 wt. % allow the emergence of several important insights. A comparison to the observed photovoltaic performance arising from the individual components aids in further clarifying the impact of DES chemistry and solution viscosity on photovoltaic and charge carrier diffusion characteristics. Finally, we introduce the DES guaniline-consisting of a 1:1 molar ratio mixture of choline chloride with guanidinium thiocyanate-demonstrating it to be a superior DSSC electrolyte over those formulated from the three most widely studied canonical DESs at all water contents investigated.

Experimental study and thermodynamic modeling of phase equilibria of systems containing cyclohexane, alcohols (C4 and C5), and deep eutectic solvents

Liquid-liquid equilibrium (LLE) data were measured and comparatively analyzed for six ternary mixtures of (cyclohexane + alcohols + deep eutectic solvents) at T = 298.2 K and p = 101 kPa. In this work, three choline chloride-based deep eutectic solvents (ChCl-DESs) were prepared for the extraction of the two structurally similar primary alcohols (1-butanol and 3-methyl-1-butanol) from a hydrocarbon (cyclohexane). The chosen DESs were DES1 (ChCl-propylene glycol with molar ratio = 1:3), DES2 (ChCl-ethylene glycol with molar ratio = 1:2), and DES3 (ChCl-glycerol with molar ratio = 1:2). The quality of the tie-line compositions was checked using the Othmer-Tobias correlation equation. The NRTL model was successfully applied to fit the experimental equilibrium data. The model binary interaction parameters were optimized by the Particle Swarm Optimization (PSO) algorithm. The model validation confirms that all the calculated parameters are consistent with the experimental data. Evaluation of the capacities of the deep eutectic solvent was carried out via the calculation of solute distribution coefficients and selectivity from the LLE data. The influence of the chemical structure of the alcohol on the phase equilibria was investigated. The extraction ability of the studied deep eutectic solvents displays promising results. The highest solute distribution coefficients were determined for (cyclohexane + 1-butanol + DES1).

Structural studies of Myceliophthora Thermophila Laccase in the presence of deep eutectic solvents

In this work, we elucidated the interactions between Myceliophthora thermophila laccase and deep eutectic solvent (DES) by crystallographic and kinetics analyses. Four types of DESs with different hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD), including lactic acid: betaine, glycerol: choline chloride, lactic acid: choline chloride and glycerol: betaine was used. The results revealed that different DES have different effects on laccase activity. Lactic acid-betaine (2:1) DES has shown to enhance laccase activity up to 300 % at a concentration ranged from 2% to 8% v/v, while glycerol: choline chloride and lactic acid: choline chloride DES choline chloride-based DES have found to possess inhibitory effects on laccase under the same concentration range. Detailed kinetic study showed that glycerol: choline chloride DES is a S-parabolic-I-parabolic mixed non-competitive inhibitor, where conformational changes can occur. The crystal structures of laccase with lactic acid: choline chloride DES (LCDES) were obtained at 1.6 Å. Crystallographic analysis suggested that the addition of LCDES causes changes in the laccase active site, but the increase in water molecules observed in the resulting crystal prevented laccase from experiencing drastic structural change. Fluorescence and circular dichroism spectroscopies were also applied to determine the effects of DES on the structural conformation of laccase. The results have confirmed that the presence of DES can trigger changes in the local environments of the amino acids in the active site of laccase which contributes to the changes in its activity and stability.

Choline Chloride-based Deep Eutectic Solvents for Degradation of Waste Cotton Fibrics to 5-Hydroxymethylfurfural

Choline Chloride-based Deep Eutectic Solvents for Degradation of Waste Cotton Fibrics to 5-Hydroxymethylfurfural

A comprehensive computational and principal component analysis on various choline chloride-based deep eutectic solvents to reveal their structural and spectroscopic properties.

In this study, the quantum chemical properties, nonbonding interactions, and spectroscopic insights of a wide variety of choline chloride (ChCl)-based deep eutectic solvents were investigated employing molecular dynamics (MD), density functional theory, and spectroscopic analyses. Nine experimentally reported ChCl-based deep eutectic solvents (DESs) were selected for this study where ChCl was common in all the DESs and the hydrogen bond donors (HBDs) were varied. The most energetically favorable cluster was selected using MD simulation followed by density functional theory calculation. The most stable cluster structures were fully optimized, and their quantum chemical properties and IR spectra were computed at the ωB97XD/6-31G++(d,p) level of theory. Principal component analysis was performed to distinguish their behavioral differences and to find out if any correlation exists among the 1:1 and 1:2 clusters. The atom-atom radial distribution functions based on MD simulations revealed that several hydrogen bonds were formed among the donor and acceptor molecules. However, the most prominent hydrogen bonds were found to be N-HHBD⋯Cl- for ChCl:U, ChCl:TU, and ChCl:Ace and O-HHBD⋯Cl- for ChCl:Glu, ChCl:Ma, ChCl:Ox, ChCl:Gly, and ChCl:Phe. Both N-HHBD⋯Cl- and O-HHBD⋯Cl- were major interactions for ChCl:Pro, where Cl- worked as a bridge between Ch+ and the respective donors. In addition, the -OH of Ch+ showed strong intermolecular interactions with the acceptor groups of the donor molecules, such as C=O and O-H. This study has tried to extract a pattern of the contributions of HBDs by comparing the structural, spectroscopic, and thermodynamic properties of ChCl-based DESs, which have also been successfully correlated with the intermolecular interactions.

L-proline-catalyzed Knoevenagel reaction promoted by choline chloride-based deep eutectic solvents

L-proline-catalyzed Knoevenagel reaction promoted by choline chloride-based deep eutectic solvents

Absorptive separation of HCl gas by choline chloride-based deep eutectic solvents

Effective separation of HCl from industrial tail gas is of great importance for its reclaim and high value utilization. For this, absorption behavior of HCl gas in three choline chloride (ChCl)-based deep eutectic solvents (DESs), i.e. ChCl-urea, ChCl-glycerol (Gly), and ChCl-glycolic acid (GA), was studied, and the stability and absorption mechanism were analyzed by 1H NMR, 13C NMR, TG and FT-IR spectra, respectively. The gas solubility of HCl in ChCl-urea, ChCl-Gly and ChCl-GA is 0.457, 0.255, and 0.214 g-HCl/g-DESs, respectively at 303.15 K and 101.3 kPa, being consistent with their decreasing basicity. The H-bonding and pseudo chemical interaction between HCl and the basic groups with lone-pair electron (–NH2, C=O, Cl-, and –OH) of DESs is responsible for the high solubility of HCl. The absorption isotherm of HCl in ChCl-Urea follows the Langmuir equation with some irreversible desorption amount due to the pseudo chemical nature. In contrast, the absorption of HCl in ChCl-Gly and ChCl-GA is physical and reversible. Viscosity of the DESs was reduced and the density increased notably with HCl absorption. ChCl-Gly is more viable for adsorption of HCl-bearing gas considering its high thermal stability, lower viscosity, and reversible absorption/desorption characteristics.

Extraction of tomato pomace with "green" solvents and evaluation of antioxidant properties

Most conventional organic solvents are toxic and pose high risks to human health. In this context, green solvents, such as deep eutectic solvents (DES), are promising and environmentally friendly. DES exhibit the advantages of ionic liquids and, in addition to being inexpensive, are low- or non-toxic, renewable and often biodegradable. The most important by-product generated from the vegetable industry is the so-called pomace that still contains a large number of bioactive compounds of great interest, such as phenolic compounds which have antioxidation properties. Antioxidant compounds are known as molecules that are able to stabilize, inhibit, deactivate and scavenge free radicals, thus protecting the human body against oxidative damage. In this study, a choline chloride-based deep eutectic solvent was used in ultrasound-assisted extraction of "green" organic compounds from tomato pomace (Lycopersicon esculentum. Mill.). Characterization HPLC-DAD methods were employed and total phenolic (TPC) and total flavonoid compounds (TFC) were assayed. Various experimental techniques including DPPH and ABTS radical scavenging activity were used to characterize the antioxidant activity of the extract. The phenolic content of the extracts was determined by the Folin–Ciocalteu method. The results also indicated the highest antioxidant activities measured in terms of 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging (40%) and 2,2′-azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS)(50%), as well as highest total phenolic content (TPC) (11.12 ± 0.02 mg gallic acid equivalent/g fresh weight). For this reason, in the future, the use of eutectic solvents may be the best method for the extraction of organic compounds from tomato pomace.

Are choline chloride-based deep eutectic solvents better than methyl diethanolamine solvents for natural gas Sweetening? theoretical insights from molecular dynamics simulations

Molecular dynamics simulations were performed to investigate the performance of three deep eutectic solvents (DESs) in the separation of acid gases from natural gas. To evaluate the efficiency of these DESs, their performance was compared with that of the conventional methyl diethanolamine (MDEA) system. For this purpose, the acidic DES (phenyl propionic acid and choline chloride; with 67 mol % Phpr), same acidic DES accompanied by boron-nitride nanotube (Nano-DES), and acidic DES with methyl diethanolamine (DES-MDEA) were considered. The solubility selectivity and diffusion selectivity were evaluated and compared to those of MDEA system. The Nano-DES system showed the best performance in terms of solubility selectivity of H2S over CH4, while the high solubility selectivity of CO2 over CH4 was obtained for pure DES systems. Likewise, the aqueous MDEA and the DES-MDEA systems exhibited the largest diffusivity selectivity of H2S over CH4 and CO2 over CH4, respectively. These results were rationalized and explained by analyzing the density profile and interaction energies. Besides, the radial and spatial distribution function, Gaussian normalized distribution of measured dipole moment of species, and the orientation of dipole moment species were investigated to explain the obtained results. Furthermore, dynamical properties such as mean square displacement and corrected diffusion coefficient of species indicated that CO2 molecules diffuse faster than H2S for studied systems except for aqueous MDEA. Likewise, the diffusion coefficient of H2S and CO2 in the considered systems follow the trends Nano-DES < DES-MDEA < DES < MDEA < aqueous MDEA, and DES < DES-MDEA < MDEA < Nano-DES < aqueous MDEA in the liquid phase, respectively.

Separation and encapsulation of Persian red rose oil by eutectic compounds

In this work, the applicability of eco-friendly choline chloride-based deep eutectic solvents (DESs) in the extraction of β-phenylethyl alcohol (PEA) as the main ingredient of red rose oil from Iranian red rose blossoms have been investigated for the first time and the results were compared to the several conventional organic solvents including tetrahydrofuran (THF), n-hexane, cyclohexane, methyl ethyl ketone (MEK) and isobutyl alcohol (iBuOH). The Iranian red rose oil compositions were determined using the gas chromatography (GC) technique. The main compounds of Iranian red rose oil were PEA (63–69%), citronellol (10–11%), geraniol (8–9%), heptadecane (0.5–5%), nerol (4–5%), nonadecane (0.5–2.5%), methyl eugenol (2–3%), eugenol (2.5–3%) and benzyl alcohol (0.9–1.1%). The results indicate that choline chloride:sucrose DES with (1:2) mole ratio performs better in the extraction of PEA than the conventional solvents. The results were confirmed using Hansen solubility parameters (HSP) and the activity coefficient model. The extracted red rose oil was encapsulated for the first time in N-butyl palmitate/stearate (BPS) with a 24.6 °C melting point as the thermosensitive shell. The narrow particle size distribution of the produced nanocapsules of (70–550) nm were found.

Mechanism of Deep Eutectic Solvent Delignification: Insights from Molecular Dynamics Simulations

Based on the field of ReaxFF, the pretreatment of a lignin–carbohydrate complex model in a choline chloride-based deep eutectic solvent was proposed. The results showed that the β-O-4 ether and glycosidic bonds in the model were broken at an optimal temperature of 373 K. The best pretreatment solvent was choline chloride/lactic acid (1:2), and 40% of the model compounds were decomposed. Free protons in deep eutectic solvents were one of the critical factors in the process of biomass delignification, and thus acidic hydrogen binding donors generally had a high lignin removal rate, but there was no significant correlation with the acidity of the hydrogen bonding donors. In the deep eutectic solvents of choline chloride/lactic acid, the delignification effect tended to decrease with the increase of lactic acid content. The delignification effect of monocarboxylic acid hydrogen bond donors decreased with the increasing molecular chain length, while the opposite effect of delignification was observed for dicarboxylic acids. The molecular dynamics simulations showed that choline chloride/glycerol (1:2) with a slightly weaker hydrogen bonding network could bind better and solubilize the product molecules, with interaction energies of −170.89 and −61.99 kJ/mol with carbohydrates and phenolic compounds, respectively.

Deep eutectic solvents used as catalysts for synthesis of 1,10-phenanthroline by improved Skraup reaction

In this study, three different choline chloride-based deep eutectic solvents were synthesized. And it is the first time to synthesize 1,10-phenanthroline through an improved Skraup reaction using deep eutectic solvent as the new catalyst from acrolein and 8-aminoquinoline. The deep eutectic solvents were characterized by Fourier transform infrared (FT-IR), 1H nuclear magnetic resonance (1H NMR), pH/mV meter, and thermogravimetric analysis (TGA). The research results show that the deep eutectic solvent formed by sulfanilic acid and choline chloride has the strongest acidity and highest catalytic active among the three deep eutectic solvents. Besides, the impacts of reaction parameters and molar ratio of raw materials on the reaction were also investigated. Under the optimized reaction conditions, the maximum selectivity and yield of 1,10-phenanthroline were achieved as 84.6 and 75.6%, respectively. The synthesis method, meanwhile, also has simple preparation process and low cheaper catalyst raw. Replacing traditional sulfuric acid and hydrochloric acid with deep eutectic solvents (DESs) as new catalysts provides a more efficient, greener and more economical strategy for the synthesis of 1,10-phenanthroline by a new improved Skraup reaction.

An efficient, cost-effective, and magnetically recoverable copper catalyst for O-arylation of phenols with aryl halides in choline chloride-based deep eutectic solvents

Silica-coated magnetite nanoparticles were functionalized with aminopropylsilyl groups and then condensed with 2-benzoylthiophene to produce a NS Schiff base chelating ligand for complexation of Cu (II) species. Characterization of the synthesized nanocomposite was performed by several spectroscopic and microscopic analyses to reveal its physical and chemical properties. It was applied as an efficient heterogeneous catalyst in promoting O-arylation reaction of phenols with aryl halides for the synthesis of diaryl ethers using deep eutectic solvents (DESs) based on choline chloride as reaction media. The catalyst and DES could be easily recycled up to five times without a significant effect on the reaction progress. The use of green and recoverable reaction medium, easy work-up, easy separation of the catalyst with the assistance of an external magnetic field, short reaction times, and high yields of products are the main merits of this protocol.