Choline Chloride-based Deep Eutectic Solvents Research Articles

Development of deep eutectic solvent extraction method for extraction of Zn2+ from powdered milk and baby formula samples and its determination by ICP-OES

In the present study, the deep eutectic solvent-based extraction method has been developed for separation of Zn prior to ICP-OES analysis. Five different choline chloride-based deep eutectic solvents were prepared. The Zn extraction ability of DESs from milk powder and baby formulation samples which contain a high amount of milk protein was investigated. The parameters affecting the extraction efficiency such as the amount and type of solvent, extraction time and ambient temperature were optimized. Oxalic acid-based DES gave the highest yield and reproducible results and appropriate preparation criteria. It is concluded from the results that DES-oxalic can quantitatively extract Zn from milky samples. The analytical parameters such as linear calibration range, limit of detection (4.2 µg L−1) and quantification (14.1 µg L−1) were also calculated. The added-found method is successfully applied to ERM BD 150 standard reference material, and the recovery values and standard deviation values were found between the ranges of 79.4–97.21 µg L−1 and 4.1–6.31 µg L−1, respectively. The method was also applied to real samples, and the recovery values were found between 73 and 106% in the spiked samples.

One pot synthesis of 2,6-bis(2/4-hydroxyphenyl)piperidin-4-one derivatives using greener deep eutectic solvent media and their characterization

An efficient one pot synthesis of 2,6-bis(2/4-hydroxyphenyl)piperidin-4-one have been studied by employing a greener, glucose-urea deep eutectic solvent (DES) as a reaction medium. Usually choline chloride-based DESs are used as a solvent for organic synthesis. In this work, some 2,6-bis(2/4-hydroxyphenyl)piperidin-4-one derivatives were produced using a real greener solvent of glucose-urea DES. Glucose-urea DES does not leave any harmful organic pollutants to the environment during synthesis and hence considered to be a real green solvent. Piperidin-4-one derivatives have found more applications in pharmacological field. Here we report the greener method for the synthesis of 2,6-bis(2/4-hydroxyphenyl) piperidin-4-one derivatives, starting from 2 and 4-hydroxybenzaldehyde with different ketones such as 2-propanone, 2-butanone, 2-pentanone and 3-pentanone in presence of ammonia. All the five compounds (a – e) as given in Scheme 1 synthesised by this method were characterised by FT- IR, 1HNMR and 13CNMR spectral methods. The yields of the products were found to be better as compared to other methods available in the literature. The melting points of the compounds were also determined. Thus, the use of glucose-urea DES as a reaction medium provides advantages in terms of simple synthetic procedure and as well as yields are obtained with good atom economy.

Enantioselective Sulfoxidation of Thioanisole by Cascading a Choline Oxidase and a Peroxygenase in the Presence of Natural Deep Eutectic Solvents.

A bienzymatic cascade for selective sulfoxidation is presented. The evolved recombinant peroxygenase from Agrocybe aegeritra catalyses the enantioselective sulfoxidation of thioanisole whereas the choline oxidase from Arthrobacter nicotianae provides the H2 O2 necessary via reductive activation of ambient oxygen. The reactions are performed in choline chloride-based deep eutectic solvents serving as co-solvent and stoichiometric reductant at the same time. Very promising product concentrations (up to 15 mM enantiopure sulfoxide) and catalyst performances (turnover numbers of 150,000 and 2100 for the peroxygenase and oxidase, respectively) have been achieved.

A choline chloride-based deep eutectic solvent promoted three-component synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3-d] pyrimidinone (thione) derivatives

An efficient one-pot method for the synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3-d]pyrimidinone (thione) derivatives through a three-component reaction between aldehydes, malononitrile and enolizable C–H activated acidic compounds using a new deep eutectic solvent made of choline chloride, urea and thiourea as an environmentally benign catalyst has been reported. The structure of the catalyst was characterized using FT-IR, 1H NMR, and 13C NMR. The present method exhibits some notable advantages such as ease of the preparation and handling of the catalyst, low cost, green reaction conditions, short reaction times, high yields, and simple work-up. Also, the catalyst could be recovered easily and recycled up to four times without significant loss of catalytic activity.

Using Choline Chloride-Based DESs as Co-Solvent for 3,5-Bis(trifluoromethyl) Acetophenone Bioreduction with Rhodococcus erythropolis XS1012

(S)-3,5-Bistrifluoromethylphenyl ethanol((S)-BTPE) is a key pharmaceutical intermediate of the NK-1 receptor antagonist. The asymmetric bioreduction of 3,5-bis(trifluoromethyl) acetophenone (BTAP) to (S)-BTPE using Rhodococcus erythropolis XS1012 has been established in a phosphate buffer system. To overcome the problem of unsatisfactory yields at high substrate concentration, deep eutectic solvents (DESs) have been introduced to the buffer system. After screening 13 kinds of choline chloride-based DESs, [choline chloride][urea] ([ChCl][U]) showed great influence on the cell activity and significantly increased the cell membrane permeability. Subsequently, some major parameters for this reaction were determined. A remarkable (S)-BTPE yield of 91.9% was gained at 150 mM substrate concentration under optimized reaction conditions with >99.9% product enantioselectivity. Compared to reduction in a buffer system, the developed [ChCl][U]-containing system increased the yield from 82.6% to 91.9%. It maintains a yield of 80.7% with the substrate concentration up to 300 mM, compared to only 63.0% in buffer system. This study demonstrated that [ChCl][U] is a feasible co-solvent to improve the bioreduction process.

Deep eutectic solvents applied in the extraction and stabilization of rosemary (Rosmarinus officinalis L.) phenolic compounds

Most conventional organic solvents are toxic and offer high risks to human health. In this context, green solvents, such as deep eutectic solvents (DES), have been developed as a promising environmentally-friendly solvent capable of replacing organic ones, mainly in the extraction and purification of biomolecules. In this study, four choline chloride-based deep eutectic solvents were used in ultrasound-assisted extraction of phenolic content from Rosmarinus officinalis L. The solvents were glycerol:choline chloride (1:2 v/w) and water (10% w/w) - CGH; lactic acid:choline chloride (1:3 v/w) and water (10% w/w) - CALH; 1,2-propanediol:choline chloride (1:2 v/w) and water (10% w/w) - CPH; and oxalic acid:choline chloride (1:1 v/w) and water (10% w/w) – CAOH. Pure ethanol was used for comparison. The antioxidant capacity, as well as the kinetic degradation, were evaluated for each of the extracts obtained. Although the extract obtained with CGH had the lowest value of total phenolic compounds (TCP), all DES-based extracts presented higher antioxidant capacity than the alcohol extract (DPPH and FRAP assays). In addition, the kinetic degradation assay demonstrated that the ethanol extract had the lowest stabilization capacity of the phenolic compounds present in the extract. The kinetic degradation of phenolic compounds was well described by the Weibull model for all extracts evaluated. Therefore, it has been possible to show that chloride-based deep eutectic solvents can be used as green solvents to substitute for organic solvents, mainly in the extraction and stabilization of phenolic compounds from Rosmarinus officinalis L.

Efficient extraction and determination of prenylflavonol glycosides in Epimedium pubescens Maxim. using deep eutectic solvents.

The Epimedium herb, Yinyanghuo in Chinese, is a famous Chinese herbal medicine. In this study, an efficient extraction method was developed for the extraction of major bioactive constituent epimedin A, epimedin B, epimedin C and icariin from E. pubescens Maxim. using deep eutectic solvents (DESs). A series of choline chloride-based DESs were synthesised for the extraction of four target compounds. DES composed of lactic acid and choline chloride with the ratio of 2:1 was selected as the most promising. Three vital factors affecting the extraction yields including water content, volume of DES aqueous solution and extraction time were optimised systematically by Box-Behnken experimental design in combination with response surface methodology. A high-performance liquid chromatography ultraviolet (HPLC-UV) method was developed for the sensitive and accurate quantification. The optimal extraction conditions were obtained as follows: water content of 17.5% (v/v), volume of DES aqueous solution 3.14 ml, and extraction time of 21 min. Under the optimal extraction conditions, the developed DES method could supply almost the same extraction yield as 50% ethanol, which were 98%, 99%, 97%, 96% for epimedin A, epimedin B, epimedin C and icariin, respectively. The present study exhibited high efficiency in extraction of prenylflavonol glycosides in E. pubescens Maxim. Thus, DESs could be used as an alternative for efficient extraction and quantification of biologically active components from natural medical plants.

Norharmane prototropism in choline chloride-based deep eutectic solvents

Deep eutectic solvents (DESs) are gaining widespread attention as novel and alternate solvents in chemical and biological sciences. Prototropic equilibria are known to be governed by the solubilizing milieu, and thus, it is imperative to study them within DESs. Prototropic behavior of β-carboline commonly named as norharmane (9H-pyrido[3,4-b]indole) is investigated in eight different DESs constituted of the salt choline chloride with eight different H-bond donors (HBDs) to ascertain their role in controlling prototropism within DESs. UV–vis molecular absorbance is used to obtain information on ground-state prototropism whereas steady-state and time-resolved fluorescence are used to investigate prototropic forms in the excited-state. In the ground-state, DESs with HBDs glycerol and ethylene glycol support both neutral and cationic forms of norharmane, however, within DESs constituted of HBDs urea, 1,4-butane-diol, and acetamide, respectively, only the neutral form exists. Within the remaining three DESs with HBDs tetraethylene glycol, 3-phenylpropionic acid, and malonic acid, respectively, only cationic form is supported. As the cationic form is preferred more over the neutral form of norharmane in the excited-state, DESs with HBDs tetraethylene glycol, 3-phenylpropionic acid, and malonic acid, respectively, support only cationic form in the excited-state. DES with glycerol also supports only the cationic form in the excited-state, DES with ethylene glycol, acetamide, and 1,4-butane-diol support both cationic and neutral forms. The DES with urea as the HBD is the only DES that supports only the neutral form in the exited-state. Excited-state intensity decay data confirms the presence of different prototropic forms of norharmane within investigated DESs with distinct decay times for the neutral and cationic forms. Correlation between the common empirical solvent polarity parameter, ETN, along with Kamlet-Taft parameters, H-bond donating acidity (α) and H-bond accepting basicity (β), of the DESs and the relative presence of the norharmane prototropic forms is established.

Fully Biosourced Materials from Combination of Choline Chloride-Based Deep Eutectic Solvents and Guar Gum

This study describes biosourced binary materials which synergize the attributes of guar gum, a vegetal galactomannan, with the ones of deep eutectic solvents (DES). The preparation of a library of ...

Tailor-made natural deep eutectic solvents for green extraction of isoflavones from chickpea (Cicer arietinum L.) sprouts

Natural deep eutectic solvents (DESs) have received increasing attention in recent years as emerging green solvents for efficient extraction of bioactive compounds from natural resources. In this study, we aimed to evaluate the potential and effectiveness of DESs with different polarities for extraction of isoflavones from chickpea sprouts. To this end, we examined 20 different DESs based on choline chloride, betaine, and l-proline as hydrogen bond acceptors in combination with different hydrogen bond donors (carboxylic acids, alcohols, sugars, and amine). Extraction efficiency was evaluated based on the extraction yields of four isoflavones (ononin, sissotrin, formononetin, and biochanin A), total flavonoid content, and anti-oxidant activity. On the basis of the results obtained, choline chloride-based DESs containing propylene glycol as a hydrogen bond donor (molar ratio of 1:1) with 30% (v/v) of water was the most effective at extracting isoflavone compounds from chickpea sprouts, compared to conventional solvents. Subsequently, in order to examine the factors contributing to optimal ultrasound-assisted extraction conditions, a Box-Behnken design paired with response surface methodology was implemented. DES water content and extraction temperature were accordingly found to have prominent effects on the extraction yields of isoflavones. Our results indicate that DESs can be used as suitable green solvents for extracting bioactive compounds from various biomaterials.

Betaine-based deep eutectic solvents with diol, acid and amine hydrogen bond donors for carbon dioxide absorption

Deep eutectic solvents (DESs) are known as alternative green solvents due to their ease of synthesis, availability, biodegradability and negligible volatility. DESs consisted of betaine as the hydrogen bond acceptor with 1,2-propanediol, levulinic acid and methyl diethanolamine (MDEA) as the hydrogen bond donors, were prepared in 1:3 and 1:6 molar ratios. The carbon dioxide solubilities in these DESs were determined using a volumetric apparatus at 313.15 K and 6 bar. The results show that CO2 solubilities in betaine-based DESs are higher than the reported CO2 solubilities in choline chloride-based DESs, for DESs having the same hydrogen bonding donor and an identical or similar composition. The viscosity and polarity of hydrogen bond donors affected the ability of deep eutectic solvent to absorb carbon dioxide. The betaine-MDEA deep eutectic solvent, with molar ratio of 1:6, has the highest absorption capacity of 0.0814 mol CO2/mol DES, measured at 313.15 K and 6 bar.

Liquid–Liquid Equilibria for Benzene/Thiophene + Cyclohexane/Hexadecane + Deep Eutectic Solvents: Data and Correlation

The experimental liquid–liquid equilibria (LLE) for several systems containing benzene or thiophene + cyclohexane or hexadecane + choline chloride-based deep eutectic solvents (DESs) including mono-, di-, and triethanolamines and mono-, di-, and triethylene glycols were measured at T = 298.15 to 308.15 K and atmospheric pressure. The distribution coefficients (β) and selectivities (S) were calculated to evaluate the efficiency of the studied solvents for aromatics (benzene or thiophene) extraction from nonaromatic phases. Generally, the selectivity values decrease with increasing of the temperature for our studied DESs. The Othmer–Tobias equation was used to ensure the consistency of the obtained LLE data. The nonrandom two-liquid (NRTL) and universal quasi-chemical (UNIQUAC) models were used to correlate the experimental LLE data. The Hansen solubility parameters confirm the performance of the studied DESs for benzene and thiophene extraction. The measured LLE data in this study shows better performance ...

Photophysical Behavior and Fluorescence Quenching of l-Tryptophan in Choline Chloride-Based Deep Eutectic Solvents.

Intrinsic fluorescence from l-tryptophan (l-Trp) is routinely used to obtain insight into the structural features and dynamics of proteins and enzymes. In contrast to aqueous enzymology, different parameters that control and influence the behavior of proteins and enzymes in nonaqueous media depend heavily on the solvent. Detailed analysis of the intrinsic fluorescence from l-Trp dissolved in two deep eutectic solvents (DESs), reline and glyceline, prepared by mixing salt choline chloride with H-bond donors urea and glycerol, respectively, in a 1:2 molar ratio within 298.15-358.15 K temperature range, is presented. Fluorescence emission maxima of l-Trp dissolved in DESs show bathochromic shift with increasing temperature. In comparison to water and several organic solvents, the fluorescence quantum yields of l-Trp in both DESs are significantly higher. While the rates of nonradiative decay in the two DESs are comparable and increase with increasing temperature, radiative decay rates are independent of temperature and are higher in glyceline than in reline, resulting in a higher fluorescence quantum yield of l-Trp in glyceline. Excited-state emission intensity decays of l-Trp fit best to a double exponential model irrespective of the identity of the DES and temperature. Average lifetime decreases with increasing temperature due to increased thermal deactivation; however, this decrease is much slower in DESs as compared to that in water. Both steady-state fluorescence anisotropy and rotational reorientation times for l-Trp are governed by the inherent complexity of the DESs as solubilizing milieu resulting in noncompliance to simple hydrodynamic treatment. Fluorescence quenching of l-Trp by acrylamide in reline is purely dynamic in nature. This is in contrast to the aqueous media where the decrease in fluorescence is a combined result of both dynamic and static quenching. The quenching within reline is fairly efficient considering the high viscosity of the medium. Significantly lower activation energy of the bimolecular quenching process as compared to the activation energy of the viscous flow indicates facilitation of the electron/charge transfer quenching of l-Trp by acrylamide within the ionic environment offered by reline. The effect of high viscosity is partly overcome by the strongly ionic environment of reline during the electron/charge transfer between l-Trp and acrylamide. The results highlight the structural complexity of these DESs especially within the cybotactic region of the probe, which is absent in common molecular solvents of similar high viscosity.

The Mechanism of Electropolishing of Niobium from Choline Chloride-based Deep Eutectic Solvents

The Mechanism of Electropolishing of Niobium from Choline Chloride-based Deep Eutectic Solvents

Sustainable Green Procedure for Extraction of Hesperidin from Selected Croatian Mandarin Peels

The peels of Citrus reticulata Blanco mandarin cultivars of different Croatian varieties (Zorica rana, Chahara, Okitsu, Kuno) were extracted using 15 different choline chloride-based deep eutectic solvents (DESs) at 50 °C for 30 min and with 20% water addition. The extracts were analyzed by high performance liquid chromatography with diode array detection (HPLC-DAD) to determine the most suitable DES for the extraction of hesperidin in the samples. The screening results indicated that choline chloride: acetamide (1:2) provided the most efficient hesperidin extraction (112.14 mg/g of plant), while choline chloride:citric acid (1:1) solvent showed the lowest hesperidin yield (1.44 mg/g of plant). The Box–Behnken design was employed to optimize extraction parameters for each variety of mandarin peel, including extraction time, temperature and water content on hesperidin extraction. The results indicated that hesperidin content in mandarin peels was completely variety-dependent. Being a novel and efficient green media for hesperidin extraction, deep eutectic solvents could also serve as promising solvent systems for the production of extracts rich in bioactive compounds.

NMR study of choline chloride-based deep eutectic solvents

Nowadays, the eutectic liquids (DESs) are considered an adequate alternative to the traditional solvents. Therefore, there is an increasing interest in the study of the structure, properties and applications of these mixtures. In this paper, several NMR spectroscopic techniques have been used in order to evaluate the molecular structure of three ternary DESs, composed of choline chloride, urea or glycerol or ethylene glycol, and water. The use of routine and non-routine NMR techniques, such as 1H, 13C, correlation experiments, NOESY, ROESY, and diffusion experiments gave us some important evidences pointing to a supramolecular structure of the DES, which may be the origin of their particular behaviour. The mixture containing ethylene glycol shows the feeblest structure. In these ternary solvents, the water is found within the structure that is still retained when DESs are diluted at 10% wt.

Synthesis of novel α-acyloxyamides using choline chloride-based deep eutectic solvent

The Passerini three-component reaction between acenaphthylene-1,2-dione, alkyl isocyanides, and carboxylic acids, leading to the formation of α-acyloxyamides in common organic solvents (CH2Cl2, MeOH) and choline chloride-based deep eutectic solvent, is described. The reaction in the latter solvent proceeded faster compared to common organic solvents. The structure of a typical product was confirmed by X-ray crystallography.

Polarity-dependent extraction of flavonoids from citrus peel waste using a tailor-made deep eutectic solvent

Choline chloride-based deep eutectic solvents (DESs) were used as green alternatives to conventional organic solvents for extracting valuable flavonoids from citrus peel waste. The effects of viscosity, pH, and polarity of DESs on the extraction efficiency were investigated. Results revealed linear dependence of extraction yield of citrus flavonoids on the polarity of the hydrogen bond donor (HBD). To simultaneously and effectively extract polymethoxylated flavonoids (PMFs) and glycosides of flavonoids (GoFs) with different polarities, five ternary DESs were designed and prepared by combining the effective HBD components. Among the tailor-made DESs studied, choline chloride–levulinic acid–N-methyl urea showed the highest extraction yield of total flavonoids. Under optimized extraction conditions, 18.75 mg/g PMFs and 47.07 mg/g GoFs were extracted from citrus peel with recoveries of 95.87% and 86.32%, respectively. This study presents a useful strategy based on tailor-made DESs to selectively extracted value-added flavonoids from waste peels in the citrus-processing industry.

Computing solubility parameters of deep eutectic solvents from Molecular Dynamics simulations

The solubility parameter (SP) of a solvent is a key property that measures the polarity and quantifies the ‘like-dissolves-like’ principle, which is an important rule in chemistry for screening solvents for separation processes. It is challenging to experimentally obtain solubility parameters of non-volatile solvents like ionic liquids (ILs), deep eutectic solvents (DESs), and polymers. Here, Molecular Dynamics (MD) simulations have been used to compute the Hildebrand and Hansen solubility parameters of DESs, which are green solvents with potential applications in many different fields. The results from MD simulations are compared with limited available experimental data and commonly used SP correlations for non-volatile solvents. Very limited information is available in literature for the vapor phase composition of DESs. Solubility parameters are computed based on the vaporization of hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) components of the DESs as well as clusters, consisting of HBD and HBA components. The relatively large SPs computed from MD indicate that the investigated choline chloride-based DESs are polar solvents. The values of SPs are not significantly affected by temperature. A comparison of vaporization enthalpies of HBD, HBA and clusters from the DES mixture suggests that it is more likely for HBD molecules to vaporize from the DES mixture and dominate the vapor phase.

Effective devulcanization of ground tire rubber using choline chloride-based deep eutectic solvents

The effect of deep eutectic solvents (DES) in devulcanization of ground tire rubber (GTR) was explored for the first time in this work. Three different DESs, namely ChCl:Urea, ChCl:ZnCl2 and ZnCl2:Urea were prepared and their physicochemical properties were examined. GTR was mixed with various DESs which were further sonicated and heated at various time intervals. The treated GTR was analyzed by energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM) and thermogravimetric analysis (TGA). Additionally, the extent of devulcanization was assessed using soluble fraction, cross-link density and related by Horikx theory. The relation between DESs’ viscosities towards devulcanization efficiency was also evaluated.