Natural Deep Eutectic Solvents Research Articles

Synergistic effect of drying methods and ultrasonication on natural deep eutectic solvent extraction of phytochemicals from African spinach (Amaranthus hybridus) stem.

The study evaluated the combined effects of drying methods (air drying [AD], hot AD [HAD], microwave drying [MD], and freeze-drying [FD]) and ultrasonication parameters (sonication temperature [STemp]: 40, 50, and 60°C) and heating time (STime: 60 and 120min) on natural deep eutectic solvent (NADES) extraction of phytochemicals from Amaranthus hybridus stem. Increasing the STemp increased the extraction yield (ECY) of the phytochemicals for all drying methods but increase in the heating time reduced the ECY slightly. MD combined with 60°C ST showed the highest ECY (53%), whereas HAD combined with 40°C ST had the lowest ECY (18%). At 60min heating time, increasing the ST from 40 to 50°C increased the total phenolic content (TPC) in the extract for most drying methods except MD, and a sonication time of 120min showed a slightly higher TPC, especially for MD samples. At 60min sonication, total flavonoid content (TFC, 800mgQE/g) was highest for AD plus 50°C ST and lowest for AD combined with 60°C (100mgQE/g), whereas for 120min sonication, MD and AD with 50°C showed the highest TFC (690mgQE/g). FD retained better some of the vitamins (thiamine, riboflavin, niacin) but MD retained better vitamin C. The antioxidant capacity was not so much different among the drying methods except for FD, which showed lower values. These results provide a theoretical basis for the synergistic applications of drying and ultrasonication during NADES extraction of phytochemicals from Amaranthus hybridus.

Natural deep eutectic solvent-based dispersive liquid-liquid microextraction of pesticides in drinking waters combined with GC-MS/MS detection

The current research aims to develop a new analytical method applying a dispersive liquid-liquid microextraction (DLLME) assisted by vortex and using an environmentally friendly extractant for the preconcentration of organochlorine and organophosphorus pesticides followed by gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis. The extractant (i.e., natural deep eutectic solvent (NADES)) is safe, cheap, biodegradable and can be prepared by simply mixing DL-menthol and decanoic acid (molar ratio 2:1). The main experimental factors affecting the extraction of all analytes evaluated (19 organochlorine and organophosphorus pesticides) have been optimised using a multivariate analysis consisting in two steps: a Plackett-Burman design followed by a central composite design (CCD). Seven experimental factors have been evaluated: (i) sample volume; (ii) NADES volume; (iii) sample pH; (iv) extraction time; (v) centrifugation time; (vi) centrifugation speed; and (vii) ionic strength (NaCl %, w v−1). For the significant variables, the optimum values were 10 mL sample and 45 μL NADES. No pH adjustment as well as addition of NaCl were needed. The other variables were set at 3 min extraction time, 5 min centrifugation time and 900×g centrifugation speed, respectively. Under the optimised extraction conditions, the limit of quantification (LOQ) values ranged between 0.2 and 78 ng L−1 for all analysed pesticides. Furthermore, the proposed analytical method has been successfully applied to drinking water (bottled spring water). The recovery study (n = 3) has been evaluated at 0.1, 1.0 and 5.0 μg L−1 spiking levels, obtaining relative recovery values within the range of 70 % and 117 % and RSD values between 1 % and 20 % for all the analytes studied, except for p,p-DDT (56–77 % in high conductivity water samples).

Development of Thin Film Microextraction with Natural Deep Eutectic Solvents as 'Eutectosorbents' for Preconcentration of Popular Sweeteners and Preservatives from Functional Beverages and Flavoured Waters.

An eco-friendly method for the determination of sweeteners (aspartame, acesulfame-K) and preservatives (benzoic acid, sorbic acid, methylparaben, ethylparaben) in functional beverages and flavoured waters using thin film microextraction (TFME) and high-performance liquid chromatography with UV detection (HPLC-UV) was proposed. A series of fourteen green and renewable solidified natural deep eutectic solvents (NADESs) were prepared and tested as 'eutectosorbents' in TFME for the first time. In the proposed method, the NADES containing acetylcholine chloride and 1-docosanol at a 1:3 molar ratio was finally chosen to coat a support. Four factors, i.e., the mass of the NADES, pH of the samples, extraction time, and desorption time, were tested in the central composite design to select the optimal TFME conditions. Limits of detection were equal to 0.022 µg mL-1 for aspartame, 0.020 µg mL-1 for acesulfame-K, 0.018 µg mL-1 for benzoic acid, 0.026 µg mL-1 for sorbic acid, 0.013 µg mL-1 for methylparaben, and 0.011 µg mL-1 for ethylparaben. Satisfactory extraction recoveries between 82% and 96% were achieved with RSDs lower than 6.1% (intra-day) and 7.4% (inter-day). The proposed 'eutectosorbent' presented good stability that enabled effective extractions for 16 cycles with recovery of at least 77%. The proposed NADES-TFME/HPLC-UV method is highly sensitive and selective. However, the use of a solid NADES as a sorbent, synthesized without by-products, without the need for purification, and with good stability on a support with the possibility of reusability increases the ecological benefit of this method. The greenness aspect of the method was evaluated using the Complex modified Green Analytical Procedure Index protocol and is equal to 84/100.

Ultrasonic-Assisted Water-Rich Natural Deep Eutectic Solvents for Sustainable Polyphenol Extraction from Seaweed: A Case Study on Cultivated Saccharina latissima.

This case study introduces a green, 1 h single-step method using water-rich natural deep eutectic solvent (WRNADES) for ultrasound-assisted extraction (UAE) of polyphenols fromSaccharina latissima, a commercially cultivated brown seaweed. The extraction efficiency was evaluated using a selective quantitative NMR method (s-qNMR) and the traditional nonselective colorimetric total phenolic content assay (TPC). Initial 6 h extractions in traditional solvents (methanol, ethanol, acetone, and ethyl acetate) showed a 40-60% increase in polyphenolic yields in 50% aqueous solutions measured by the TPC method. Six different water-rich (50%) NADES (WRNADES) combinations were tested (choline chloride/betaine with lactic acid, citric acid, and 1,3-butanediol), with betaine and 1,3-butanediol (1:1) proving most effective. Parameters for the WRNADES were optimized using Box-Behnken design response surface methodology, resulting in a 1:20 w/w biomass to solvent ratio and a 1 h extraction time at 50 °C. The WRNADES extraction process was refined into a scalable, single-step procedure and compared with traditional solvent extractions (6 h, 50% aqueous methanol and acetone). A final XAD-7 polyphenol recovery step was included in all extractions. The optimized WRNADES extraction yielded 15.97 mg GAE/g of the dry weight recovered polyphenolic extract (s-qNMR), exceeding the 6 h 50% aqueous methanol (12.4 mg GAE/g) and acetone (11.4 mg GAE/g) extractions. Thus, the UAE-WRNADES method presented in this case study provides a cost-effective, sustainable, and eco-friendly alternative for the extraction of phenolic compounds from seaweed. It promotes the development of environmentally friendly production processes within the seaweed biorefinery.

Optimizing the microwave-assisted extraction and ultrasonic-assisted processes to acquire flavonoid and phenolic compounds from watermelon rinds using natural deep eutectic solvents

ABSTRACTS This study extracted flavonoids and phenolics from watermelon fruit by microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) combined with a natural deep eutectic solvent (NADES). The effectiveness of NADES combined with UAE and MAE was evaluated for extracting these compounds from watermelon rinds. The study chose a 2:1 molar ratio of hydrogen bond donors (HBDs) to hydrogen bond acceptors (HBAs). Among the tested combinations, 1,2-propanediol-lactic acid showed the highest solubility for flavonoids and phenolics within the extraction system. Experiments with a single factor were used to examine the effects of different parameters on total phenolic content (TPC) and total flavonoid content (TFC). The Box-Behnken design (BBD) model optimized the NADES-based UAE and MAE processes based on TPC and TFC responses. The results of the experiment and the predicted values from the BBD agreed well. Optimal conditions for recovering phenolics and flavonoids from watermelon rinds with NADES-based UAE were determined as 1/60 g/ml for SLR, 300 W, 20% water content, and 15 min, while NADES-based MAE: 1/50 g/ml for SLR, 400 W, and 3 min. This study presents an efficient approach for extracting biologically active compounds from watermelon.

Evaluation of Polyphenol Profile from Citrus Peel Obtained by Natural Deep Eutectic Solvent/Ultrasound Extraction

Citrus fruits are widely consumed worldwide; however, one of their primary uses is juice production, resulting in over 40 million tons of agro-industrial waste. Citrus peel is the main agro-industrial by-product in citrus production. In recent years, secondary metabolites of interest, mainly polyphenols such as hesperidin, have been identified in citrus peels. Currently, green alternatives like natural deep eutectic solvents (NADES) based on choline chloride and glucose (Glu), combined with ultrasound-assisted extraction, are studied to obtain polyphenol-rich extracts with potential health applications. This study aims to evaluate the effect of: (1) molar ratios (MR) of 1:0.5, 1:1 or 1:2 mol/mol of choline chloride (ChCl):glucose (Glu); (2) the percentage of added water (WA: 50, 60 or 70%) to NADES; and (3) different citrus peels of Citrus aurantium (bitter orange), Citrus sinensis (sweet orange), and Citrus limon (lemon) used for extraction, on polyphenol profiles, total polyphenol content (TPC), and antioxidant capacity (Ax) of the extracts. The extracts were analyzed using ultra-performance liquid chromatography (UPLC) and evaluated using the Folin–Ciocalteu method for TPC and DPPH assay for quantifying AC. A factorial experimental design 33 was implemented. The extract obtained with an MR of 1:1 (ChCl:Glu) from Citrus aurantium peel exhibited the highest concentration of hesperidin (2003.37 ± 10.91 mg/100 g dry mass), whereas an MR of 1:2 (ChCl:Glu) exhibited the highest concentration of neohesperidin (1045.94 ± 1.27 mg/100 g dry mass), both using 60% WA. This extract also showed the highest antioxidant capacity, achieving 100% inhibition. On the other hand, the highest concentration of total phenolic content (TPC) (96.23 ± 0.83 mg GAE/100 g dry mass) was obtained using C. aurantium peel with an MR of 1:0.5 (ChCl:Glu) and 60% WA. The extracts also presented high concentrations of rutin and catechin. These findings highlight the potential of revalorizing citrus peels, particularly Citrus aurantium, and their extracts obtained with NADES for possible health applications.

Natural Deep Eutectic Solvents as Absorbing Solution and Preparation Solvent of Perovskite Nanocrystals Simultaneously for CH3I Gas Visual Sensing.

Methyl iodide (CH3I) gas as a toxic gas causes great harm to organisms due to its high volatility and high reactivity with biological nucleophiles. Unfortunately, the sensing and detection of CH3I gas are challenging because of the diffusive nature of the gases and its low concentrations in the environment. Herein, we have developed a fast, green, and sensitive CH3I gas visual sensing method based on the capture technology of toxic gases by natural deep eutectic solvents (NADESs) coupled to the halide rapid exchange capability of perovskite nanocrystals (PNCs). In this strategy, NADESs are used as an absorption solution to adsorb gaseous CH3I, while simultaneously exposing I- through the action of the nucleophilic reagent; then, CsPbBr3 PNCs were synthesized in NADESs and used as sensing material to achieve I- exchange. Benefiting from the capture and enrichment of CH3I gas, the sensitivity of the gas sensor was highly improved. The sensor exhibited the lowest detection limit (limits of detection) of 164.15 μmol/m3, below the minimum safe level for human inhalation, which is 200 μmol/m3. This breakthrough offers greater possibilities for the quantitative detection of CH3I gas.

Antioxidant and antidiabetic activities of Zingiber officinale var. Rubrum extracted with natural deep eutectic solvents

Polyphenols and flavonoid compounds are known to have antioxidant activity and can reduce blood glucose levels. Zingiber officinale var. Rubrum is one of the plants with high polyphenol content. This study aimed to extract phenolic and flavonoid compounds from this plant with various solvents primarily natural deep eutectic solvents (NADES), namely 70% ethanol, NADES1 [citric acid: sucrose (1:1)], NADES2 [sucrose: glucose: fructose (1:1:1)], NADES3 [choline chloride: glycerol (1:2)], and NADES4 [glycerol: urea (1:1)]. The phenolic and flavonoid levels were determined using spectrophotometer, the antioxidant activity was measured using DPPH and Ferric Reducing Antioxidant Power (FRAP) methods, while the antidiabetic activity was evaluated using enzymatic assay of α -amylase and α-glucosidase enzymes. The findings indicated that all NADES outperformed 70% ethanol in extracting phenols, with NADES1 showing the highest phenolic content. Meanwhile, the highest flavonoid content was observed in extracts with 70% ethanol and NADES1. The results of antioxidant activity analysis using DPPH revealed that extracts with 70% ethanol, NADES1, and NADES4 exhibited considerable strength (IC50: 45-49 µg/mL), with the average values of the three solvents being not significantly different. From the results of the FRAP assay, NADES3 demonstrated the highest strength Antioxidants Activity Index (AAI: 29.24±3.08 mmol/g), whereas 70% ethanol showed the lowest strength (AAI: 22.76±5.23 mmol/g). The average AAI values for all solvents indicated no significant differences. Among the solvents, NADES1 exhibited very strong inhibitory activity against α-amylase (19.62±0.20 µg/mL), while for α-glucosidase, NADES1 was stronger (IC50: 57.36±6.08 µg/mL) than other solvents. In conclusion, NADES can be a promising tool for extracting secondary metabolites from Zingiber officinale var. Rubrum as it shows both antioxidant and antidiabetic activities.

Investigating the Use of Natural Hydrophobic Deep Eutectic Solvents for Extracting Carotenoids from Food and Food By-products

Abstract In today’s food industry, the demand for sustainable methodologies in producing health-promoting natural products is rising. Traditional extraction techniques are increasingly deemed unreliable due to environmental concerns. To address these challenges, the scientific community has developed Green Chemistry , a specialized branch that aims to minimize or eliminate hazardous processes and substances in industrial applications. One promising and eco-friendly alternative emerging from Green Chemistry is the use of NaDESs which are prepared with natural components, generally recognized as safe (GRAS), and offer an environmentally benign option for various industrial processes. They are characterized by their biodegradability, low toxicity, and ability to be tailored for specific applications, making them an ideal choice for green extraction methods. In this context, NaHDESs have shown significant potential as extracting media for bioactive compounds, particularly carotenoids, from food and food by-products. Carotenoids, known for their antioxidant properties and health benefits, are highly sought after in the food and nutraceutical industries. Traditional extraction methods often rely on organic solvents, which pose environmental and health risks. In contrast, NaHDESs offer a safer and more sustainable alternative. This study explores the definition, properties, and applications of NaHDESs, with a particular focus on their use in extracting carotenoids. By examining various food and vegetable by-products, the research aims to evaluate the solvent’s efficiency and effectiveness in this application. The findings could pave the way for eco-friendly extraction techniques in the food industry, aligning with the principles of Green Chemistry and addressing the growing demand for natural and health-promoting products. Information © The Author 2024

Structural and physicochemical characterisation of binary glutamine-based deep eutectic solvents

Amino acid-based deep eutectic solvents (AADES) are a new subclass of natural deep eutectic solvents with prospective applications especially in the energy and pharmaceutical industries. In this study, binary DESs were formulated, for the first time, from glutamine and lactic acid by the heating and stirring method. Subsequently, the effect of varying molar ratios of the DES components on their physicochemical, structural and thermal properties was evaluated. In this regard, the refractive index, water content, conductivity, viscosity and pH of the formulated DESs were analysed. Furthermore, the thermal stabilities of the DESs were determined using differential scanning calorimetry and thermogravimetry analysis, while the hydrogen bond interactions within the solvents were elucidated using nuclear magnetic resonance (1H and 13C NMR) and Fourier transform infrared spectroscopy (FTIR). Results showed that the densities (1.25–1.29 g/cm3), refractive indices (1.45–1.48), conductivity (0.19–0.51 mS cm−1), water contents (3.88–7.87 %), viscosities (867.34–8712.50 mPa·s) and pHs (1.85–3.37) of the DESs were significantly influenced by lactic acid. The NMR and FTIR spectra profiles confirmed the interactions of the hydrogen bond forming groups within the DESs. In addition, the solvents showed stability at room temperature up to 100 °C, after which decomposition set in until 400 °C; however, they formed no crystals between −40 °C and 100 °C. The glass transition phase of the DESs was also observed at −20 °C which highlights the potential application of the solvents in cryopreservation. Thus, this study presents valuable insights into the proposed utilisation of these GL-based DESs as sustainable solvents in industrial applications.

Extraction of Anthocyanin from Purple Sweet Potato Using Ultrasound-Assisted Natural Deep Eutectic Solvents and Its Application for Smart Packaging Film

Extraction of Anthocyanin from Purple Sweet Potato Using Ultrasound-Assisted Natural Deep Eutectic Solvents and Its Application for Smart Packaging Film

Bioactivity and application potential of O/W emulsions derived from carboxylic acid-based NADES-extracted total saponins from Polygonatum cyrtonema Hua

This study focuses on evaluating new methods for the green extraction of saponin compounds from Polygonatum cyrtonema Hua (PCH). This study utilized a combination of carboxylic acid-based natural deep eutectic solvents (NADES) and various extraction techniques including conventional heat reflux-, ultrasound-, and microwave-assisted extraction. The primary objectives were to assess total saponin yield, antioxidant capacity, and enzyme inhibition efficiency. Additionally, the solvents and extracts were evaluated for their antibacterial activity. Oil-in-water (O/W) emulsions of NADES extracts were also characterized and analyzed for stability. Results indicated that three NADES systems were effective in extracting saponins, with choline chloride and lactic acid (ChCl-LA) system being the most efficient. The ChCl:LA extract exhibited antimicrobial and antioxidant activities superior to conventional organic solvent extracts. Additionally, it demonstrated maximum inhibitory activity (IC50 values: 0.98 ± 0.03 and 1.46 ± 0.07 mg/mL, respectively) against α-glucosidase and α-amylase. The NADES extract as an aqueous phase significantly improved the stationarity of the O/W emulsion. Collectively, the study highlights the antimicrobial and technological advantages of NADES as a potential solvent for extracting saponin compounds from PCH.

Natural deep eutectic based dispersive liquid-liquid microextraction and solidified floating organic drop for cadmium determination by electrothermal atomic absorption spectrometry with multivariate optimization (DLLME-SFOD-NADES-ETAAS)

A novel method was developed for cadmium determination based on dispersive liquid-liquid microextraction and solidified floating organic drop by multivariate optimization with electrothermal atomic absorption spectrometric detection using a natural deep eutectic solvent (NADES) of (L)-menthol and formic acid. Important factors, including pH, final concentration of PAN, mole ratio of formic acid, volume of NADES, type of dispersive solvent, and vortex time, were assessed using two-level fractional factorial design (FFD), and circumscribed central composite design (CCC). The analytical performance parameters, encompassing linearity range, limit of detection (LOD), limit of quantification (LOQ), and precision, were evaluated. The linearity range ranged from 0.72 to 2.50 ng/L, with corresponding LOD and LOQ values of 0.22 and 0.72 ng/L, respectively. Precision was evaluated by conducting three replicates of the three concentration levels, resulting in %RSD values of 11.8 %, 5.1 %, and 3.9 %, respectively. An enrichment factor (EF) of 112 was achieved. The optimized method was applied for cadmium determination in various matrices, including drinking water, environmental water, seafoods, yielding %recovery in the ranges of 78.05–102.41 %. Finally, comparison of t-values between the developed method and CRMs demonstrated satisfactory results at a 95 % confidence level.

Electron beam irradiation coupled ultrasound-assisted natural deep eutectic solvents extraction: A green and efficient extraction strategy for proanthocyanidin from walnut green husk

Proanthocyanidin (PAC) is recognized as a potent natural antioxidant that prevents various diseases. As societal awareness increases, eco-friendly and efficient natural product extraction technologies are gaining more attention. In this study, an electron beam irradiation (EBI) coupled with ultrasound-assisted natural deep eutectic solvents (NADES) extraction method was developed to enable the green and highly efficient extraction of PAC from walnut green husk (WGH). NADES, prepared with choline chloride and ethylene glycol, demonstrated excellent extraction capacity and storage stability for PAC. Molecular dynamics simulations elucidated the high compatibility between NADES and PAC, attributed mainly to a higher SASA value (207.85 nm2), a greater number of hydrogen bonds (330.99), an extended hydrogen bonding lifetime (4.54 ps), and lower inter-molecular interaction energy. Based on these findings, the optimal conditions (13 kGy EBI, 42 mL/g liquid-solid ratio, 38 °C extraction temperature, 70 min extraction time) resulted in a maximum PAC extraction yield of 56.34 mg/g. Notably, this yield was 32.93 % higher than that observed in samples not treated with EBI and ultrasound-assisted extraction (UAE). Analysis of tissue morphology, extract functional groups and thermal behavior suggested a possible mechanism for the synergistically enhanced PAC extraction by the EBI-NADES-UAE method. Additionally, the PAC extracted using the NADES by the EBI coupled with ultrasound-assisted method exhibited outstanding antioxidant activity (comparable to Vc), digestive enzyme inhibition (IC50: 17–0.61 mg/mL), and anti-glycation capacity (IC50: 86.49 μg/mL). Overall, this work provided a green and efficient strategy for PAC extraction from WGH, elucidated the extraction mechanism and bioactivities, and offered valuable insights for potential industrial applications.

The total tannins of Geum japonicum Thunb. var. chinense extracted by green and natural deep eutectic solvent: Extraction optimization, component identification and hypoglycemic activity

Geum japonicum Thunb. var. chinense (G. japonicum) is a cultivated medicinal plant and used as folk medicine, among which tannins are the main active ingredients. In this work, L-proline-lactic acid (Pro:La) as natural deep eutectic solvents (NADESs) was tailored for the total tannins extraction from G. japonicum with the optimal conditions as follows: water content of 29 %, solid-liquid ratio of 27:1 (mg/mL), extraction time of 48 min, and extraction temperature of 48°C. In high fat diet-induced obese mice, the total tannin extract of G. japonicum can significantly reduce the body weight and serum lipid levels, improve glucose tolerance impairment and insulin resistance, reduce islet hypertrophy and protect the liver. Targeted fractionation of the total tannin extract of G. japonicum led to the isolation of sixteen tannins. Notably, the isolated tannins, except for ellagic acid and 3,3′-di-O-methylellagic acid, possessed strong α-glucosidase inhibitory activities (IC50: 1.401–4.801 μg/mL) and dose-dependently inhibited glucose consumption of Caco-2 model system in vitro. These results indicate that the NADES (Pro:La) can effectively extract total tannins from G. japonicum and provide a reference for further applications in medicine and healthcare products.

Deep Eutectic Solvents and Natural Deep Eutectic Solvents for Extraction and Purification of Proteins from Animal and Botanical Sources - A Review

Deep Eutectic Solvents and Natural Deep Eutectic Solvents for Extraction and Purification of Proteins from Animal and Botanical Sources - A Review

Advanced Extraction Techniques Combined with Natural Deep Eutectic Solvents for Extracting Phenolic Compounds from Pomegranate (Punica granatum L.) Peels.

Pomegranate (Punica granatum L.) peel is a potential source of bioactive phenolic compounds such as ellagic acid and α- and β-punicalagin. This work explores the efficiency of natural deep eutectic solvents combined with ultrasound-assisted extraction (UAE) and pressurized liquid extraction (PLE) for their extraction. Five NaDESs were evaluated by employing UAE (25 °C, for 50 min) to determine their total phenolic content (Folin-Ciocalteu assay) and ellagic acid and α- and β-punicalagin contents (high-performance liquid chromatography (HPLC-DAD)). The NaDES composed of choline chloride (ChCl) and glycerol (Gly) (1:2, molar ratio) was the most efficient in the UAE when compared with the rest of the NaDESs and water extracts. Therefore, ChCl:Gly was further evaluated using PLE at different temperatures (40, 80, 120 and 160 °C). The PLE-NaDES extract obtained at 80 °C for 20 min at 1500 psi exhibited the highest contents of ellagic acid and α- and β-punicalagin compared to the rest of the temperatures and PLE-water extracts obtained under the same extraction conditions. Combining UAE or PLE with a NaDES emerges as a sustainable alternative for extracting ellagic acid and α- and β-punicalagin from pomegranate peel.

Spectrophotometric Determination of Cobalt(II) by Natural Deep Eutectic Solvent (NADES) Air-Assisted Dispersive Liquid-Liquid Microextraction (AA-DLLME)

Cobalt is beneficial for human activity but has adverse effects when discharged in large quantities. Therefore, its precise and accurate quantification in samples is of importance. Here, a natural deep eutectic solvent (NADES), composed of camphor (H-bond acceptor) and menthol (H-bond donor), has been used for the preconcentration of Co(II) from water samples before determination by a spectrophotometer at 398 nm. The 8-hydroxyquinoline-Co(II) complex was transferred to the NADES using air-assisted dispersive liquid-liquid microextraction (AA-DLLME). The extraction efficiency was enhanced through fine tuning of various parameters, including pH, NADES volume, and quantity of dispersant. Similarly, the centrifugation rate and time, quantity of the complexing agent, matrix effects, and salt concentration were also evaluated. Under the optimized conditions, an enrichment factor of 37.5 and a preconcentration factor of 37.5 were obtained. The limits of detection (LOD) and quantification (LOQ) were 0.44 µg/L and 1.47 µg/L, respectively. For seven replicates of 50 µg/L Co(II), the relative standard deviation was 3.2%. The developed method was employed for the determination of Co(II) in water samples, with quantitative recovery values from 94.5 to 98.5%.

Using natural deep eutectic solvents for the extraction of antioxidant compounds from cornelian cherry (Cornus mas L.) fruits

Traditionally used extraction methods are usually based on toxic and/or flammable solvents. Therefore, currently, increased attention has been focused on environmentally friendly green extraction techniques. We aimed to develop a green extraction procedure by using natural deep eutectic solvents (NADES) to recover antioxidant compounds from cornelian cherry fruits (Cornus mas L.). Natural deep eutectic systems combined with maceration with shaking extraction were tested to recover of antioxidant compounds from cornelian cherry fruits. In this study, four different independent variables, namely solvent type (Glu-CA; Glu-Gly; LA-Glu), water concentration (30, 50, and 70 %; v/v), extraction time (30, 60, 90, and 120 min), and extraction temperature (25, 40, and 50 °C) were investigated. Glucose-glycerin (Glu-Gly; 1:1 M ratio) based solvent provided the best results. In addition, one-factor-at-a-time (OFAT) optimization showed that a temperature of 25 °C, 120 min of extraction time, and water concentration of 50 % (v/v) to be the best extraction parameters for Glu-Gly based NADES extraction. The developed method has been successfully applied for the extraction of antioxidant compounds from 13 different cornelian cherry cultivars. NADES can be used safely to extract phenolic compounds from cornelian cherry fruits compared to conventional extraction solvents (water and 80 % (v/v) ethanol).

Amino acid based natural deep eutectic solvents: An efficient catalyst and solvent for N-acetyl-d-glucosamine conversion into organonitrogen chemicals

Organonitrogen chemicals are widely used and in great demand in the food, pharmaceutical and chemical industries. Hence, it is important to develop green and efficient synthesis paths to organonitrogen chemicals for their use as new resources. Herein, we propose the preparation of organonitrogen chemicals from chitin biomass monomer N-acetyl-d-glucosamine (GlcNAc) promoted by natural deep eutectic solvents (NADESs). The selective generation of 3-acetamido-5-(1′,2′-dihydroxyethyl) furan (Chromogen III) and 3-acetamido-5-acetylfuran (3A5AF) from GlcNAc was achieved by the design of NADESs components. GlcNAc reacts in binary NADES proline-glycerol (Pro-Gly) to generate 26 % of Chromogen III and 39 % of 3A5AF in ternary NADES proline-glycerol-lactic acid (Pro-Gly-LA). In addition, the intermolecular hydrogen bonds in NADESs were confirmed through 1H diffusion-ordered spectroscopy (DOSY) NMR technology. And the results of 13C NMR chemical shift titration indicated interaction between NADESs and the C3 and C6 position of GlcNAc. Based on the NMR experiments a mechanism is proposed.