Preconcentration of liposoluble constituents in Salvia Miltiorrhiza using acid-assisted liquid phase microextraction based on a switchable deep eutectic solvent

A review of green solvents for the extraction and separation of bioactive ingredients from natural products

Bioactive substances from natural products are good resources from the pharmaceutical and food industries. Conventional organic solvents are widely used for extracting and separating bioactive substances. Recently, various environmentally friendly solvents have been developed and applied in the separation field to replace conventional organic solvents. This review focuses on environmentally friendly solvents for the extraction and separation technologies that meet the requirements of green chemistry. The classifications, applications, influencing factors, and mechanisms involved in the extraction processes using these green solvents are also discussed. Green solvent-based extraction systems are promising alternatives to traditional organic solvents. Green solvents are mild and non-destructive to the active compounds during their application and have negligible effects on the ecosystem when discharged. The use of green solvents for the extraction and separation of active ingredients in natural products is attracting attention because of their low environmental impact and sustainability.

An overview of hydrophobic deep eutectic solvents driven liquid-phase extraction: Applications and prospects

Deep eutectic solvents (DESs) are a type of emerging green solvent. They are simple to prepare, cost-effective, highly atom-efficient, exhibit extremely low toxicity, and are biodegradable. Since their discovery, DESs have attracted significant interest from the scientific community across various fields. In recent years, these solvents have been extensively studied by researchers as extraction media. Hydrophobic deep eutectic solvents (hDESs) first appeared in the literature in 2015 and represent a group of DESs that meet the requirements of green chemistry. hDESs have great potential in the fields of separation and extraction and are considered effective alternatives to replace hydrophilic DESs and other hydrophobic organic solvents for the extraction of lipophilic natural products. This review summarizes pioneering and innovative work on hDESs, including the latest research progress regarding their applications, extraction techniques, and recycling methods. It also highlights issues that need to be addressed in the future. The results of hDESs in natural product extraction and the extraction of other compounds have revealed their significant potential as alternative green solvents in industrial separation processes.

Deep Eutectic Solvent Extraction Assisted Ligand Affinity Assay for α-Glucosidase Inhibitors Screening From the Plasma of Rats Administrated Pueraria lobata Extracts

In this work, for the first time, a deep eutectic solvent assisted ligand affinity assay was proposed. Several critical parameters affecting the analysis performance were investigated and the optimized DES extract conditions were as follows: the solution of tetrabutylammonium chloride-ethylene glycol (1:2) was prepared as an extract solution. A total of 1.4 mol/L sodium citrate (pH = 6.6) was used for phase separation, and the vortex extraction time was 5 min. Analytes could be enriched in the phase of deep eutectic solvent after phase separation. Then, they could be analyzed by α-glucosidase immobilized magnetic beads affinity assay directly. Results showed the proposed method could detect luteolin (a positive control) from plasma selectively. The LOD was 2 µg/mL. The intraday precision and the interday precision were 7.86% and 6.66%, respectively. By using the proposed method as a tool, plasma of the rats that administrated the extract of Pueraria lobata was analyzed. The bio-active flavonoids absorbed in the body such as puerarin, daidzin, daidzein, and a metabolite of puerarin (puerarin glucuronide) were found. The method has the benefits of a simplified analytic process, high resolution, and is a reliable method.

Deep eutectic solution elution assisted ligand affinity assay: A useful tool for the active coumarins screening from Fructus cnidii

BACKGROUND

Many of the ligand affinity analyses are presented in water environment, and the hydrophilic solution such as methanol is used for dissociating the bound compounds. The obtained dissociation solution needs to be concentrated for improving the sensitivity of the assay. However, it is not good for the analysis of hydrophobic and volatile compounds such as coumarins. The solubility of them in water environment is low. And they may be lost in the sample preparation process. In this work, a deep eutectic solvent elution assisted ligand affinity assay for the screening of active coumarins in plants was proposed.

RESULTS

For the first time, deep eutectic solvent was used as a dissociation solution for dissociating the compounds that bind with acetylcholinesterase immobilized magnetic beads. Analytes could be enriched during the phase separation process of deep eutectic solvent. The concentration of the analytes in sample solution was therefore increased. It is good for the detection of coumarins. The LOD and LOQ of the proposed assay were 0.50 (μ g/mL) and 1.50 (μ g/mL), respectively. The relative recovery of the assay was 99.4 ± 7.2 %. The intra-day and inter-day precision were 7.25 % and 6.80 %. Using the assay as a tool, the active coumarins in Fructus cnidii were analyzed. And two coumarins with acetylcholinesterase inhibition activity such as imperatorin and osthole were found.

SIGNIFICANCE

Coumarins have good solubility in the selected deep eutectic solvent, and could be enriched into hydrophobic phase during the phase separation process. The extra concentration process is not needed. Compared with traditional methods, the proposed method has the benefits of simplified operation process, high sensitivity, and is friendly to the volatile and hydrophobic compounds.

Responsive deep eutectic solvents: mechanisms, applications and their role in sustainable chemistry

In an era so focused on sustainability, it is important to improve chemical processes by developing and using more environmentally friendly solvents and technologies. Deep eutectic solvents (DES) have proven to be a promising replacement for conventional solvents. In recent years, a new type of DES has emerged that responds to various stimuli. These responsive DES (RDES) may offer all the advantages of DES while allowing the recycling and reuse of solvents. As such, RDES can further contribute to a greener future. This review provides an overview of the diverse types of RDES, their switching mechanisms and their application in several fields. Lastly, it offers a critical perspective on current shortcomings and prospects.

Switchable Deep Eutectic Solvents for the Green Extraction of Tea Saponins From Camellia Oleifera Seed Meal

Tea saponin has garnered tremendous interest for its potential use in surfactant and drug synthesis. This research was designed to develop a technique based on pH-responsive switchable deep eutectic solvents (SDESs) for extracting tea saponins from Camellia oleifera seed meal. SDES synthesized from hexanoic acid and triethanolamine (1:1 molar ratio) offered the optimum extractive performance and the optimal conditions were obtained through single-factor experiments: 30 wt% water content in SDES, solid-liquid ratio of 1:30 g/mL, 60°C extraction temperature, 30 min extraction time, and acid volume of 1500 µL. The extraction yield was 162.14 mg/g after optimization, which increased by 15.65% and 9.47% compared to water and ethanol extraction methods, respectively. After pH adjustment, 98.95% of the tea saponins were recovered in the bottom phase. After precipitation and freeze-drying procedures, the purity of the tea saponin solid was 62.9%.

Ultrasound assisted upper critical solution temperature type switchable deep eutectic solvent based liquid-liquid microextraction for the determination of triazole in water

BACKGROUND

The use of pesticides to protect crops has long been an important measure to provide healthy and safe agricultural products, but excess pesticides flow into fields and rivers, causing environmental pollution. Earlier methods utilizing organic solvent liquid-liquid microextraction for pesticide residue detection were not environmentally friendly. Therefore, it is significant to find a greener and more convenient detection method to determine pesticide residues.

RESULTS

A new method was established to detect three triazole fungicides (TFs), including myclobutanil, epoxiconazole and tebuconazole, in environmental water samples. And the determination was conducted using a high-performance liquid chromatography with the ultraviolet detector (HPLC-UV). The switchable deep eutectic solvent (SDES) can be reversibly switched between hydrophilic and hydrophobic states through temperature modulation. Additionally, the method exhibited excellent linearity for all target analytes within the concentration range of 10-2000 μg L-1, with satisfactory R2 values (≥0.9975). The limits of detection (LODs) ranged from 2.3 to 2.6 μg L-1, and the limits of quantification (LOQs) ranged from 7.8 to 8.7 μg L-1. The accuracy of the method was assessed through intra-day and inter-day precision tests, yielding relative standard deviations (RSDs) in the ranges of 2.8%-6.7% and 2.2%-7.5%, respectively. Density functional theory (DFT) results indicated that hydrogen bonding is a significant factor affecting the binding of DES with triazoles. Three different green assessment tools were used to prove that the SDES-HLLME method had good greenness and broad applicability.

SIGNIFICANCE

This is a homogeneous liquid-liquid microextraction (HLLME) method based on the upper critical solution temperature (UCST) type switchable deep eutectic solvent program, which can complete the extraction within a few minutes without dispersant. In terms of pesticide detection, the analytical method is simple and more conducive to environmental protection.

Evaluation of organo-vermiculites as sorbent phases for solid-phase extraction of ibuprofen from water

The study of ibuprofen (IBU) preconcentration was carried out making use of a homemade column for solid-phase extraction (SPE), using vermiculite (VT) or organo-vermiculites (OVTs) as sorbent phases. Aqueous samples (50.0 mL) percolated the column and IBU was sorbed onto the VT or OVT and then desorbed using acetonitrile. Employing this SPE system and OVT, calibration curves were generated for IBU, by spectrophotometric quantification using the α-naphthylamine method. R2 values higher than 0.9950 and LOD between 12 and 18 μg L-1 were observed, for real enrichment factors of 21 and 31, by using OVTs. The analytical protocol was applied to three water samples, which were spiked with IBU solutions to evaluate the precision and accuracy of the method. Recoveries between 77 and 110% at three different IBU concentrations and RSD lower than 18% were observed, even by using the spectrophotometric method. The protocol developed in this study demonstrated that the OVT was appropriate to work as a preconcentration phase for IBU determination in water samples.

A modified strategy to improve the dissolution of flavonoids from Artemisiae Argyi Folium using ultrasonic-assisted enzyme-deep eutectic solvent system

In this study, enzyme-deep eutectic solvent-assisted ultrasonic extraction technique (EnDUE) was developed for the efficient dissolution of flavonoids from Artemisiae Argyi Folium. The extraction results of Artemisiae Argyi Folium flavonoids (quercetin, luteolin, and isorhamnetin) were used as indicators to investigate the influencing factors through single factor experiment, Placket-burman design, and Box-behnken design, so as to obtain satisfactory yields. After systematic optimization, the optimal conditions for extraction of the target flavonoids were: Choline chloride/1,4-butanediol with a water content of 25%, cellulase+pectinase with a concentration of 1.6%, solid-liquid ratio of 1/32 g/mL, pH of 4.2, ultrasonic frequency of 80 kHz, ultrasonic power of 160 W, ultrasonic temperature of 40 °C, and ultrasonic time of 25 min, respectively, which derived a total yield of 8.06 ± 0.29 mg/g. Compared with the reference techniques, the proposed EnDUE technique showed significant advantages in the yield and extraction efficiency of flavonoids. In addition, after preliminary purification, the Artemisiae Argyi Folium flavonoids showed good antioxidant activity. Deep eutectic solvent (DES) can degrade the cell wall components and increase the action site of enzyme, and enzyme can promote the penetration of DES into the cell wall matrix, which is mutually beneficial to the dissolution of intracellular components. Therefore, the extraction technique proposed in this work (EnDUE) greatly promotes the dissolution of flavonoids from Artemisiae Argyi Folium, and provides theoretical support for the further application of plant flavonoids.

An effervescence-assisted switchable deep eutectic solvent based liquid-phase microextraction of triazole fungicides in drinking water and beverage

A new effervescence-assisted switchable deep eutectic solvent-based liquid phase microextraction (EA-SDES-LPME) combined with HPLC-UV was developed for determination of common triazole fungicides in drinking water and beverages, including myclobutanil, flusilazole, hexaconazole and bitertanol. The alternative extraction solvent was prepared with hexafluoroisopropanol and dipropylamine with the merits of time-saving, easy to collect and cost-effectiveness. The SDES can be reversibly switched between hydrophilic and hydrophobic states by pH adjustment. The homogeneous extraction was achieved under the hydrophilic form of SDES, and the bi-phase separation was obtained easily by adjusting pH value to restore the original hydrophobicity. Moreover, the characterization of SDES was investigated by FTIR and 1H NMR. The main variables affecting extraction efficiency were optimized in detail. Under the optimal conditions, the proposed method shows desirable precision (RSDs less than 18.5%) and acceptable recovery (72.6-95.4%). The lower limits of detection and limits of quantitation were found to be in the range of 1-2 μg L-1 and 5-10 μg L-1, respectively. The formation mechanism of SDES and the extraction mechanism for target analytes were investigated by density functional theory. The proposed methodology was simplicity, sensitive, time-saving and successfully applied to determine triazole fungicides in drinking water and beverages, making it an alternative technique for the analysis of trace analytes with satisfactory sensitivity.

A switchable deep eutectic solvent for the homogeneous liquid-liquid microextraction of flavonoids from "Scutellariae Radix"

A homogeneous liquid-liquid microextraction (HLLME) was established based on a switchable deep eutectic solvent (DES) for the preconcentration and determination of six flavonoids with different polarity in "Scutellariae Radix" combined with high performance liquid chromatography (HPLC). A switchable DES composed of N,N-dimethylethanolamine (DMEA) and heptanoic acid was used as an extraction solvent in the HLLME method, which was miscible thoroughly with the aqueous sample phase initially, and then underwent rapid phase transition induced by the addition of an inorganic acid. After the extraction, the upper hydrophobic layer was recovered for HPLC analysis. Different experimental parameters were optimized, and the optimal extraction conditions were as follows: the switchable DES extraction phase, 90 µL of DMEA-heptanoic acid (1:1 mole ratio); phase-switching trigger, 100 µL of 5 mol/L HCl; 10% (w/v) of salt concentration in sample phase; extraction time, 0.3 min. Furthermore, the structures of the switchable DES and the upper hydrophobic layer were characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy and differential scanning calorimetry to illustrate the phase-switching mechanism of the extraction phase during the extraction process. Under the optimized conditions, the enrichment factors for six target analytes were between 0.4 and 104. The calibration curves were linear (r≥0.9866) in the range of 0.033-8.65 mg/L for scutellarin, 0.022-5.77 mg/L for baicalin, 0.0033-0.865 mg/L for scutellarein and wogonoside, and 0.0022-0.577 mg/L for baicalein and wogonin, respectively. Low detection limits (≤8.0 × 10^-3 mg/L) and quantification limits (≤2.4 × 10^-2 mg/L) as well as good precisions (relative standard deviations lower than 9.2%) and acceptable accuracies (spiked recoveries 89.3-114.4%) were also obtained. The proposed method is a simple, fast, and eco-friendly sample pretreatment method.

Simultaneous capture of hydrophilic and hydrophobic compounds from complex plants by biosurfactant-assisted mechanical amorphous dispersion extraction

A biosurfactant-assisted mechanical amorphous dispersion extraction (BA-MADE) procedure was established for the simultaneous capture of hydrophilic phenolic acids and hydrophobic tanshinones from Salvia miltiorrhiza. Single-factor experiments and the response surface methodology were used to optimize and analyze the crucial parameters for the method, such as the type and amount of amorphous-dispersion extractants, grinding time, extraction time and solid-to-liquid ratio. The optimized parameter values for the BA-MADE process were 407.02 mg of sodium chenodeoxycholate, a grinding time of 4.87 min, an extraction time of 4.92 min, and a solid-to-liquid ratio of 0.5:10 g/mL. The calibration curves of danshensu, rosmarinic acid, lithospermic acid, salvianolic acid B, salvianolic acid A, dihydrotanshinone I, cryptotanshinone, tanshinone I, and tanshinone II A exhibited good linearity in the range of 1-500 μg/mL (R² ≥ 0.9990). The limits of detection of nine analytes ranged from 5.46 to 130 ng/mL, the relative standard deviations (RSDs) of intraday and interday precision were less than 1.95 and 3.56%, respectively, and the recoveries of the real sample were in the range of 85-113%, with RSD% below 3.21%. The BA-MADE method was compared with previously reported methods, such as heating reflux extraction, ultrasonic extraction and microwave-assisted micellar extraction, and the results demonstrated that the developed method has significant advantages in the simultaneous extraction of hydrophilic and hydrophobic active components from Salvia miltiorrhiza.

Extraction of parabens from personal care products using a pH-responsive hydrophobic deep eutectic solvent: experimental design and COSMO-RS evaluations

A pH-responsive hydrophobic deep eutectic solvent is used for the extraction of parabens from different personal care products.