Deep Eutectic Solvent Concentration Research Articles

A sustainable and Integrated Microbial Biocatalysis of Resveratrol from Polygonum cuspidatum Siebold & Zucc Using Cellulose-Based Immobilised Aspergillus niger with Deep Eutectic Solvent-Assisted Microreactors.

An efficient and green method was developed using deep eutectic solvent assistance to enhance the biotransformation method of producing resveratrol from Polygonum cuspidatum Siebold & Zucc, using cellulose-based immobilised Aspergillus niger in the process. Various deep eutectic solvents (DES) were screened to obtain a superior biocatalytic effect. The increase in DES concentration aggravated the degree of cell membrane damage. Natural deep eutectic solvents (NADES) exhibited a more favourable catalytic effect than DES due to their excellent biocompatibility. This enhancement is associated with the hydrogen bonding donor components present in NADES, with catalytic ability ranking as alcohol-based > sugar-based > organic acid. CHCL/EG exhibited the maximum catalytic effect at 1.0 wt%. Under optimal conditions (pH 6.5; temperature, 29.5°C; ratio of liquid to solid 20:1 (mL/g), and time 47h), the resveratrol yield reached 32.79mg/g, which was 13.06-fold to that of the untreated sample (2.51mg/g). The residual activity of the cellulose-based microreactor was 81.46% after ten trials. The proposed method was successfully employed, demonstrating higher biocatalysis efficiencies and superior environmental protection compared to conventional solvents for resveratrol biocatalysis.

Enhanced water absorption in pectin-chitosan hydrogel via modification with deep eutectic solvent: Optimisation and characterisation

Natural polymers are widely available, nontoxic, and biodegradable but have lower absorption when used to create hydrogels. Thus, a new modification of hydrogel combining pectin and chitosan was developed using choline chloride-based deep eutectic solvents (DESs) with ethylene glycol (DES1), glycerol (DES2), and acetic acid (DES3) called eutectogel. DES was added due to the hydrophilic site, which can increase water absorption. The eutectogel with each DES, including control (without DES), were optimized in their ratio of pectin to chitosan (0.5:1, 1:1, 1.5:1, and 2:1) and DES concentration (10 %, 20 %, and 30 %) to obtain the highest water absorption capacity (WAC). All developed gels showed the highest WAC at a ratio 0.5:1 of pectin to chitosan, with 20 % each of DES1, DES2, and DES3 labeled as E20, G20, and A20 having WAC values of 16.02, 13.50, and 12.50 g/g, respectively, owing to the existence of additional hydrophilic sites from DES within the gel for water binding. While the WAC value for the control was 6.2 g/g, this study proves the ability of DES to increase the WAC of E20, G20, and A20 more than two times compared to the control. E20 showed the highest water sorption because of the shorter and smaller size of ethylene glycol in DES1, with two less hindered hydroxyl groups efficiently binding with water molecules compared to glycerol and acetic acid. The interactions were observed through FTIR analysis, specifically in the amino groups of chitosan and carboxyl groups of pectin at the peak of 1636 to 1642 cm−1, which served as indicators of the electrostatic interaction with the modified DES and peak 3335 to 3350 cm−1 indicated of hydrogen bonding. The hydrogen bonding was also confirmed via DSC thermal analysis at 164.06°C to 188.44 °C. Characterization with FTIR, UV–Vis, and DSC confirmed the successful integration of DES, and it revealed that the new hydrogels had better transparency and thermal stability, with E20 showing the best overall performance in enhanced water absorption.

Deep eutectic solvent pretreatment of sugarcane bagasse for efficient lignin recovery and enhanced enzymatic hydrolysis

This study explores the sugarcane bagasse (SCB) pretreatment with two deep eutectic solvents (DESs) prepared from choline chloride (ChCl) as a hydrogen bond acceptor (HBA) to two hydrogen bond donors (HBD): oxalic acid (OA) and trifluoroacetic acid (TFA) for lignin recovery and enhancing enzymatic saccharification. The pretreatment conditions, reaction time, temperature, and DES concentration were optimized using response surface methodology. The two DESs showed a lignin yield of 74.67 ± 2.75 and 83.50 ± 2.65 mg per gm of SCB, respectively. Enzymatic hydrolysis of the cellulose-enriched material (CEM) obtained after pretreatment showed an enhanced RS yield of around 4-fold compared to the untreated SCB. The CEM was characterized using FTIR, Powder X-ray diffraction, and Scanning Electron Microscopy. The recovered lignin characteristics were studied using FTIR, 1H NMR, and 2D-HSQC NMR analysis. The FTIR spectra of lignin show the presence of aromatic skeletal vibrations, -OH, -CH, C-O stretching vibration, and aromatic C-H deformation. Furthermore, the pretreatment solvent recyclability studies were conducted to evaluate the effectiveness of DES for a sustainable biorefinery process.

Amino acids-based deep eutectic solvents as additives for improved enantioseparation in capillary electrophoresis.

In this study, several amino acids deep eutectic solvents were prepared using L-valine and L-leucine as hydrogen bond acceptors, and L-lactic acid and glycerol as hydrogen bond donors. These amino acids' deep eutectic solvents were first used as buffer additives to construct several synergistic systems along with maltodextrin in capillary electrophoresis for the enantioseparations of four racemic drugs. Compared with single maltodextrin system, the separations of model drugs in the synergistic systems were significantly improved. Some key parameters affecting chiral separation such as maltodextrin concentration, deep eutectic solvent concentration, buffer pH, and applied voltage were optimized. In order to further understand the specific mechanism of the amino acids deep eutectic solvents in improving chiral separation, we first calculated the binding constants of maltodextrin with enantiomers using the capillary electrophoresis method in the two separation modes, respectively. We also used molecular simulation to calculate the binding free energy of maltodextrin with enantiomers. It is the first time that amino acids deep eutectic solvents were used for enantioseparation in capillary electrophoresis, which will greatly promote the development of deep eutectic solvents in the field of chiral separation.

Unraveling the Role of Deep Eutectic Solvents with Varying Hydrogen-Bond Acceptors on the Thermoresponsive Polymer Poly(N-isopropylacrylamide).

Deep eutectic solvents (DESs) have emerged as promising tools for crafting polymeric materials across diverse domains. This study delves into the impact of a series of DESs on the phase behavior of poly(N-isopropylacrylamide) (PNIPAM) in aqueous environments, presenting compelling insights into their performance. Specifically, we explore the conformational phase behavior of PNIPAM in the presence of four distinct lactic acid (LA)-based DESs: LA-betaine (LA-BET), LA-proline (LA-PRO), LA-choline chloride (LA-CC), and LA-urea (LA-U). By maintaining a consistent hydrogen-bond donor (HBD) while varying the hydrogen-bond acceptor (HBA), we unravel how different DES compositions modulate the phase transition behavior of PNIPAM. Our findings underscore the profound influence of DESs comprising LA as the HBD and diverse HBAs-BET, PRO, CC, and U on the thermoresponsive behavior of PNIPAM. Employing spectroscopic techniques such as ultraviolet-visible (UV-vis) spectroscopy, steady-state fluorescence, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), ζ-potential, and transmission electron microscopy (TEM), we elucidate the preferential interactions between the HBA groups within DESs and the hydration layer of PNIPAM. Notably, temperature-dependent DLS analyses reveal a discernible decrease in the lower critical solution temperature (LCST) of PNIPAM with increasing DES concentration, ultimately disrupting the hydrogen-bond interactions and resulting in early hydrophobic collapse of the polymer, which can be clearly seen in the TEM micrographs. Furthermore, the formation of polymer composites within the mixed system leads to notable alterations in the physiochemical properties of PNIPAM, as evidenced by shifts in its LCST value in the presence of DESs. This perturbation disrupts hydrogen-bond interactions, inducing hydrophobic collapse of the polymers, a phenomenon vividly captured in TEM micrographs. In essence, our study sheds new light on the pivotal role of varying HBA groups within DESs in modulating the conformational transitions of PNIPAM. These insights not only enrich our fundamental understanding but also hold immense promise for the development of smart polymeric systems with multifaceted applications spanning bioimaging, biomedical science, polymer science, and beyond.

Comparison of deep eutectic solvent-based ultrasound- and heat-assisted extraction of bioactive compounds from Withania somnifera and process optimization using response surface methodology.

Extraction of bioactive compounds from Withania somnifera roots was studied using sodium acetate-glycerol deep eutectic solvent (DES) and two techniques ultrasound-assisted extraction (UAE) and heat-assisted extraction (HAE) under response surface methodology (RSM). For UAE and HAE, total phenolic content (TPC, mg gallic acid equivalents per g dry weight (mg GAE g-1 DW)), total flavonoid content (TFC, mg rutin equivalents g-1 DW (mg RE g-1 DW)), radical scavenging activity (RSA, mg AAE (ascorbic acid equivalents) g-1 DW), and iron chelating activity (ICA, mg EDTAE (ethylenediaminetetraacetate equivalents) g-1 DW%) were 6.51, 6.08, 12.56, and 3.57, respectively, and 3.33, 3.98. 6.57 and 2.48, respectively. For UAE, the optimal conditions were a DES concentration of 50 %, temperature of 60 °C, and time of 20 min, and for HAE, a DES concentration of 60 %, temperature of 60 °C, and time of 75 min. The discovered models were strongly supported by the validation experiments. UAE was more efficient and less time-consuming for extracting phytoconstituents of the W. somnifera than HAE.

Study on drug separation in Two-Phase aqueous systems using deep eutectic solvent consisting of choline chloride and 1,2 propanediol

Biphasic-aqueous systems have been the subject of extensive research due to their strength to simultaneously separate and purify active pharmaceutical molecules with high efficiency and purity. Aqueous Two-Phase Systems (ATPS) have been used to extract and purify cells, nucleic acids, proteins, antibodies, and tiny molecules due to their intermolecular interaction and chemical makeup. We used a deep eutectic solvent containing (choline chloride and 1,2 propanediol), K2HPO4, and water in the initial investigation of the biphasic curve of this system at the temperature of 298.15 K and atmospheric pressure. Furthermore, we used the ATPSs to study the separation of the selected pharmaceuticals. As new findings, we examined the partition coefficient and the impact of variables such as salt and the deep eutectic solvent concentration on the partitioning of the drugs. Based on the present finding, the pharmaceuticals have the propensity to be extracted in the top phase, which is rich in deep eutectic solvents. Finally, we conducted thermodynamic modeling of the present aqueous two-phase system (ATPS) using experimental liquid–liquid equilibrium data employing the nonrandom two-liquid nonrandom factor (NRTL-NRF) and NRTL models. The NRTL-NRF model can accurately correlate the aqueous two-phase system's thermodynamic behavior with the average relative deviation percent of 4.22.

Spectrally Stable Deep‐Blue Perovskite Light‐Emitting Diodes Enabled by a Deep Eutectic Solvent

AbstractFull‐color LED display requires Commission Internationale de l'Eclairage (CIE) 1931 coordinates of (0.14, 0.08), based on the National Television Standards Committee (NTSC) blue standard. However, such deep‐blue perovskite light‐emitting diodes (PeLEDs) still lag far behind in terms of device efficiency. Moreover, spectral stability remains a big challenge. To settle these issues, a kind of deep eutectic solvent (DES) is introduced as the perovskite precursor solvent additive, which is formed from a hydrogen bond acceptor (HBA) choline chloride and a hydrogen bond donor (HBD) urea via the hydrogen bond interaction. The incorporation of DES has multiple advantages, shown as follows: 1) improves the solubility of CsCl to yield dense perovskite morphology, 2) inhibits the growth of the perovskite crystal to achieve low‐n phases with narrow distribution, and 3) stabilizes the halide anions in the lattice to ensure stable electroluminescence (EL) spectra. As a result, the as‐prepared PeLED shows the maximum external quantum efficiency (EQEmax) of 2.71% with a CIE coordinate of (0.134, 0.055). With the increase in the DES concentration, the spectra stability is also obviously enhanced.

Biodiesel production through electrolysis in the presence of choline chloride-based deep eutectic solvent: Optimization by response surface methodology

In this study, a novel catalyst-free electrolysis method was developed that uses deep eutectic solvents (DESs) as both a supporting electrolyte and a cosolvent for biodiesel synthesis. Various choline chloride–based DESs for biodiesel production were prepared and tested. Among the DESs that were synthesized, DES-2 (choline-chloride-to-ethylene-glycol molar ratio of 1:2) exhibited the highest efficiency for electrolysis-based biodiesel synthesis. The DES-2-assisted electrolysis was then optimized through the application of a response surface methodology to maximize biodiesel yield. The maximal biodiesel yield of 94.71 % was obtained through electrolysis when an electrolysis voltage of 22.06 V, a DES concentration of 7.91 % (w/w), a water amount of 1.44 % (w/w), a methanol-to-oil molar ratio of 25.09:1, and a reaction time of 2 h were applied at room temperature. Notably, DES-2 could be reused for four cycles to achieve a biodiesel yield of > 80 % biodiesel. The properties of the synthesized biodiesel were verified as meeting international standards. This study suggests that electrolysis involving the use of DESs as a supporting electrolyte and a cosolvent is an eco-friendly, cost-effective, and efficient method for biodiesel synthesis.

Effect of deep eutectic solvents on the biocatalytic properties of β-glucosidase@ZnOFe nano-biocatalyst

In this work, we investigate the use of aqueous deep eutectic solvents (DESs) consisting of different hydrogen bond acceptors (choline chloride, ammonium salts or betaine) and hydrogen bond donors (amines, sugars and alcohols), as co-solvents in biocatalytic reactions catalyzed by a nano-biocatalyst with β-glucosidase (BGL) activity. For this purpose, β-glucosidase from Thermotoga maritima was immobilized on the surface of green zinc oxide-iron oxide nanoparticles (BGL@ZnOFe) derived from an aqueous olive leaf extract. The covalent bonding of β-glucosidase on the surface of nanoparticles was demonstrated by X-ray photoelectron spectroscopy. The effect of a wide range of DES solutions on the biocatalytic features of BGL@ZnOFe was thoroughly investigated. The concentration of DES as well as the specific combination of hydrogen bond acceptors and hydrogen bond donors had a significant impact on the hydrolytic activity of immobilized β-glucosidase. Most choline chloride and betaine-based DESs enhanced the enzymatic activity and thermal stability of BGL@ZnOFe up to 50%. The enzymatic activity of the nano-biocatalyst towards the hydrolysis of bioactive phenolic compounds depends on the nature of the DES used. Choline chloride:butylene glycol-based medium had beneficial effect on a transglycosylation reaction, such as the synthesis of salidroside, increasing the total turnover number of the biocatalytic process by 55%. This work indicates that the use of several choline chloride and betaine-based DESs can be successfully employed as green co-solvents in various hydrolytic and synthetic biocatalytic processes.

Effect of choline chloride based deep eutectic solvents on the aqueous solubility of 4-hydroxycoumarin drug: Measurement and correlation

This work aims to improve the aqueous solubility of 4-hydroxycoumarin (4H-coumarin) as one of the lowest soluble derivatives of coumarin, by using deep eutectic solvents (DESs). The applied DESs are composed of choline chloride (ChCl) as a hydrogen bond acceptor (HBA) and ethylene glycol (EG), urea (U), or glycerol (GLY) as hydrogen bond donors (HBD). The shake-flask method was used to determine the experimental solubility of 4H-coumarin at T = (298.15 to 313.15) K. The results demonstrate that 4H-coumarin solubility was increased noticebly at higher DES concentration and temperature. Moreover, in the presence of ChCl/EG, the 4H-coumarin solubility was more than 250 times higher than that in pure water. The experimental solubility data were fitted to the Wilson, electrolyte Non-Random Two-Liquid (e-NRTL), and UNIQUAC activity coefficient models, which shows that the Wilson model has the best correlation performance for aqueous solutions containing ChCl/EG, ChCl/GLY and ChCl/U with 0.05, 0.07 and 0.22 of ARD%, respectively. The Gibbs and van't Hoff equations to estimate the dissolution apparent thermodynamic quantities including enthalpy, Gibbs free energy, and entropy. The results indicate that 4H-coumarin dissolution processes in the investigated systems are endothermic. Quantum mechanical Density functional theory (DFT) method has also been implemented to discover the nature of the interactions in the studied DES/4H-coumarin complexes at the B3LYP-D3(BJ)/6-311g(d,p) level of theory. The DFT calculations confirm that the formations of the DESs and DES/4H-coumarin complexes are spontaneous, and the most dominant interactions are hydrogen-bonding of Cl from ChCl as electron donor and H of the other components as electron acceptor.

Physicochemical and acoustic characterization of binary mixtures of tetraalkylammonium bromide: PEG based DES and water

In modern green chemistry, Deep eutectic solvents (DESs) have gain appreciable recognition as an analogues of ionic liquids (ILs) due to inexpensive and easy to handle preparation method. DESs exhibit similar physiochemical properties to ILs and considered as a suitable alternative to volatile organic solvents. In present study, DESs were formulated by complexing HBA: Tetraethylammonium bromide and Tetrapropylammonium bromide and HBD: Polyethylene glycol of average molecular weight (200/400/600) in 1:2 M ratio. The densities (ρ), speeds of sound (u) of pure DESs and their binary mixtures with H2O were collected as a function of DES concentration and temperature. The excess molar properties: VmE and Ks,mE were calculated using these data and fitted to the Redlich-Kister equation to estimate standard deviation between the experimental and calculated values of excess molar properties. The trends of variation in calculated values of VmE and Ks,mE were interpreted in light of temperature and DES: H2O interactions occurring within the binary mixtures. The PFPT (Prigogine-Flory-Patterson Theory) and ERAS (Extended Real Associated Solution Model) were applied to evaluate the validity of theories to predict VmE for presently studied binary mixtures.

A Novel Ethanolic Two-Phase System Based on Deep Eutectic Solvents and Amphiphilic Copolymer for the Extraction of Neohesperidin and Naringin from the Pomelo Peel.

A novel ethanolic two-phase system (ETPS) composed of Pluronic®L-64 (PL 64) and deep eutectic solvents (DESs) was constructed for the separation of two similar flavonoids of naringin (Nar) and neohesperidin (Neo) from the pomelo peel. The selectivity (S) data showed that DES prepared from tetrabutylammonium bromide (N4444Br) and glycerol (Gly) had the optimal distribution efficiency for Nar and Neo standards. A binodal curve of N4444Br-Gly/PL 64/ethanol system fitted to the nonlinear Merchuk relationship showed that the biphasic region was narrow for ETPS. The influences of the mass ratio of DESs and PL 64, DES concentration, PL 64 concentration, molar ratio of DESs, temperature, phosphate buffer solution, and ethanolic pH were studied in single-factor experiments. Under the optimal conditions, the maximum extraction efficiency (ENar = 68.32%, ENeo = 86.09%), partition coefficient (KNar = 6.66, KNeo = 19.13), and S (2.88) were obtained in the DESs-rich (bottom) phase. N4444Br-Gly, Nar, and Neo with recovery yields of 78.12%, 66.61%, and 68.03%, respectively, had been recovered using D101 macroporous resin. This proposed ETPS is efficient and environmentally friendly and is expected to avail meaningful references for the separation of natural products with similar structures.

Separation and Purification of Astragalus membranaceus Polysaccharides by Deep Eutectic Solvents-Based Aqueous Two-Phase System.

(1) Background: Aqueous two-phase systems (ATPSs) have been widely used in the separation and purification of bioactive substances in recent years. (2) Methods: In this study, deep eutectic solvents (DESs)-based ATPSs were employed for the extraction and separation of Astragalus membranaceus polysaccharides (AMP). The optimal DES (choline chloride:urea = 1:1) was first screened to extract AMP, and the effect of DES concentration, solid–liquid ratio, pH, extraction temperature, and extraction time on the extraction yield of AMP were investigated. (3) Results: The maximum extraction yield was 141.11 mg/g under the optimum conditions. AMP was then preliminarily purified by ATPS, to further realize the recycling and reuse of DES. The effect of type of salts, salt concentration, and extraction temperature on extraction efficiency was investigated. The extraction efficiency was 97.85% for AMP under the optimum ATPS conditions. Finally, the obtained AMP was studied by molecular weight determination, infrared spectroscopy analysis, and monosaccharide composition analysis. (4) Conclusions: This ATPS extraction based on DESs is simple, environmentally friendly, low-cost, and has high extraction efficiency, which provides new ideas for the extraction of plant polysaccharides and other bioactive compounds.

Green extraction of caffeine from coffee pulp using a deep eutectic solvent (DES)

The objective of this work was the development of a green extraction method based on the use of a deep eutectic solvent (DES) to extract caffeine from coffee pulp (CP). Choline chloride and glycerol were used as hydrogen bond acceptor and hydrogen bond donor, respectively. ATR-FTIR and viscosity measurements were conducted for the characterization of DES mixtures. The effects of DES mixtures concentration (CDES), liquid-to-solid ratio (L/S), extraction temperature (T) on caffeine extraction yield (CCaf) and extract antiradical activity (AAR) were studied, and the extraction process was optimized. The optimum of extraction was achieved at a temperature of 55 °C, a solvent/pulp ratio of 47 mL/g, and a DES concentration of 70% w/v in aqueous solution. In addition, a mathematical model to describe the kinetic mechanisms of the extraction was developed, whereas the dependence of the best descriptive model constants on extraction variables was expressed by an appropriate model. These results would offer scientific reference for promoting the valorization of coffee pulp.

Ultrasound‐assisted extraction optimization of polyphenols, flavonoids, and antioxidant compounds from fruit of Melia azedarach using a glycerol‐based green deep eutectic solvent

For sustainable extraction of bioactive components from Melia azedarach fruit, ultrasound-assisted extraction (UAE) and a green deep eutectic solvent (DES) glycerol-ammonium acetate (GAA) were studied with optimization under response surface methodology with variables temperature, amplitude, and DES concentration (DC). The three-level, three-factorial Box–Behnken design (BBD) was applied to study three extraction conditions: temperature (30–50°C), amplitude (50%–100%), and DES concentration (50%–90%) to obtain highest level of total phenol (TP), total flavonoid (TF), iron chelating activity (ICA), and anti-radical activity (DPPH). The optimized conditions for the responses were 50°C temperature, 50% DC, and 100% amplitude and the observed values for TP, TF, ICA, and DPPH were found 17.11 mg GAE /g DW, 11.33 mg RE/g DW, 52.66%, and 72.84%, respectively. The model was strongly supported by validation study, which indicates GAA-UAE is an effective green method for extracting bioactives from M. azedarach and the lower error rates (≤5.60) between predicted and observed values for TP, ICA, and DPPH models showed that these responses are more predictable compared with those of TF. Practical applications The study proposes an ultrasound-assisted green and efficient approach for extraction of bioactive natural products from the fruit of the medicinal plant Melia azedarach. The optimized method developed can be used to obtain polyphenols, flavonoids, and other antioxidant bioactives from this abundantly available plant for industrial application for various medicinal and food preservation purposes.

Exploration of lower critical solution temperature DES in a thermoreversible aqueous two-phase system for integrating glucose conversion and 5-HMF separation

With the deepening of the research on the conversion of cellulose biomass to furfural, there is no green and efficient method to separate sugars and 5-HMF. This study utilized a thermoreversible aqueous two-phase system (ATPS) coupled with tetrabutylammonium bromide ([N4444]Br)- based deep eutectic solvents (DES) and inorganic salts for separating glucose and 5-HMF. The thermal characteristics of DESs were analyzed by thermogravimetry (TGA) and differential scanning calorimetry (DSC). The thermoreversible phase behavior of ATPS was determined by phase diagram. Furthermore, the process factors were optimized, such as the type and concentration of DES and phosphate, the temperature, and the time of ATPS were investigated, to maximize the separation of glucose and 5-HMF. Finally, the ATPS was a successful integrated catalytic reaction of glucose involving CrCl3 and 5-HMF separation. The results showed that the ATPS consist of 30 wt% [N4444]Br-EG and 25 wt% K2HPO4 had the most efficient extraction rate, 5-HMF reached 96.0 ± 0.6%, and mainly existed in the DES phase, while glucose was enriched in salt phase, and the extraction rate reached 99.9 ± 0.03%. And the 5-HMF yield reached 25.6 ± 1.1% in the production separation integrated platform. This thermoreversible ATPS may provide a guide for the effective extraction of furfural from biomass-derived glucose.

Pressurized aqueous solutions of deep eutectic solvent (DES): A green emergent extraction of anthocyanins from a Brazilian berry processing by-product

Deep eutectic solvents (DES) are emergent solvents with high extractability of bioactive compounds. Therefore, anthocyanin rich-fractions were recovered from jaboticaba peels by combining aqueous solutions of DES and pressurized liquid extraction (PLE). The extraction occurred at 10 MPa, 12 min, with conditions optimized through response surface methodology: 47% DES concentration, 90 °C, and 5.3 mL/min flow rate. PLE with different DES (choline chloride combined with propylene glycol or malic acid) solutions were compared to conventional solvents (water and acidified water) concerning yield, thermostability, antioxidant, anti-diabetic, and anti-obesity activities. DES solutions presented anthocyanin yields up to 50% higher than conventional solvents. ChCl:Ma, with the highest anthocyanin stability (Ea = 77.5 kJ.mol−1), was a promising solvent concerning color, anti-diabetic and anti-obesity potential. Environmental analysis by Green Certificate and EcoScale indicated PLE with DES solutions is a green and efficient approach to recover anthocyanin from jaboticaba peel, providing useful extracts.

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.

Cytotoxicity of some choline-based deep eutectic solvents and their effect on solubility of coumarin drug

The effect of some deep eutectic solvents (DESs) on the coumarin solubility has been investigated using Hansen solubility parameters (HSP). The solubility of coumarin was measured in aqueous systems containing some DESs based on choline chloride (ChCl) as hydrogen bond acceptor (HBA) with urea (U), ethylene glycol (EG), and glycerol (GLY) as hydrogen bond donors (HBD) by widely applied shake-flask method at T = (298.15 to 313.15) K. The results indicate that coumarin solubility enhances with the concentration of DESs and temperature. Also, coumarin was dissolved more than 80 times compared with pure water in the presence of ChCl/EG. Then experimental data were fitted to Wilson, electrolyte Non-Random Tow-Liquid (e-NRTL), and UNIQUAC activity coefficient models. Furthermore, the dissolution thermodynamic properties including enthalpy, Gibbs free energy, and entropy have been calculated based on Gibbs and van't Hoff equations. Due to these results, it is indicated that coumarin dissolution in the studied systems is an endothermic process. Moreover, to investigate the biological properties of DESs, MTT assay have been applied to determinate cytotoxicity of the DESs. In the melanoma skin cell line, cell culture tests revealed that these solvents had very low toxicity and high biocompatibility.