Simultaneous determination of curcuminoids in Curcumae Longae Rhizoma and turmeric tea using liquid-phase microextraction based on solidification of floating deep eutectic solvent drop

Deep eutectic solvents: Preparation, properties, and food applications

Deep Eutectic Solvents (DESs) emerge as innovative 21st-century solvents, supplanting traditional ones like ethanol and n-hexane. Renowned for their non-toxic, biodegradable, and water-miscible nature with reduced volatility, DESs are mostly synthesized through heating and stirring method. Physicochemical properties such as polarity, viscosity, density and surface tension of DESs influenced their application. This review paper gives the overview of application of eco-benign DESs in fruits, vegetables, cereals, pulses, spices, herbs, plantation crops, oil seed crops, medicinal and aromatic plants, seaweed, and milk for the extraction of bioactive compounds. Also, it gives insight of determination of pesticides, insecticides, hazardous and toxic compounds, removal of heavy metals, detection of illegal milk additive, purification of antibiotics and preparation of packaging film. Methodologies for separating bioactive compounds from DESs extracts are systematically examined. Further, safety regulations of DESs are briefly discussed and reviewed literature reveals prevalent utilization of DES-based bioactive compound rich extracts in cosmetics, indicating untapped potential of their application in the food industry.

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.

Deep eutectic solvents: Recent advances in fabrication approaches and pharmaceutical applications

Deep eutectic solvents (DESs) have received increasing attention in the past decade owing to their distinguished properties including biocompatibility, tunability, thermal and chemical stability. Particularly, DESs have joined forces in pharmaceutical industry, not only to efficiently separate actives from natural products, but also to dramatically increase solubility and permeability of drugs, both are critical for the drug absorption and efficacy. As a result, lately DESs have been extensively and practically adopted as versatile drug delivery systems for different routes such as nasal, transdermal and oral administration with enhanced bioavailability. This review summarizes the emerging progress of DESs by introducing applied fabrication approaches with advantages and limitations thereof, and by highlighting the pharmaceutical applications of DESs.

Facile liquid colorimetric sensor using high-density deep eutectic solvent for trace detection and speciation of iron in milk

An efficient colorimetric sensor was developed using a high-density deep eutectic solvent (HD-DES) for the trace detection and speciation of iron in various milk samples. A liquid colorimetric probe was fabricated by dissolving ferrozine (FZ) in HD-DES prepared from TBABr and PBA. The prederivatization of Fe²⁺ via complexation with FZ on the HD-DES/FZ probe provided the [Fe(FZ)₃]^4- complex, which led to a color change from pale yellow to purple before it was simultaneously extracted by HD-DES. The Fe³⁺ content was calculated by subtracting the amount of Fe²⁺ from the total Fe content following the reduction of Fe³⁺ to Fe²⁺ by L-ascorbic acid in an acid buffer. Under the optimized conditions, the proposed colorimetric sensor exhibited appreciable linearity in the concentration range of 0.003-0.04 mg L^-1, a low limit of detection (0.95 µg L^-1), high enrichment factor (50), and outstanding repeatability. The liquid colorimetric probe was successfully applied for the determination and speciation of iron in milk samples, and the results were compared with those obtained using the standard atomic absorption spectrometry method. Moreover, quantitative analysis was performed on a smartphone using the Image J application to estimate the color intensity change, which eliminated the requirement of sophisticated scientific instruments.

Solvent terminated natural deep eutectic solvent microextraction for concentration of curcuminoids in Curcumae Longae Rhizoma and turmeric tea

A novel solvent terminated microextraction method based on a natural deep eutectic solvent (L-menthol and lactic acid at a molar ratio of 1:2) coupled with HPLC was proposed, which was utilized for the separation and enrichment of bisdemethoxycurcumin, demethoxycurcumin and curcumin in Curcumae Longae Rhizoma and turmeric tea. The effects of independent parameters on extraction efficiency were optimized by single-factor analysis. Subsequently, four predominated parameters affecting extraction procedure, including extractant volume, salt concentration, demulsifier consumption and demulsification time, were further evaluated by central composite design. Under the optimized conditions, the linear ranges of calibration curves were 0.005-0.5 μg/mL for bisdemethoxycurcumin, 0.004-0.4 μg/mL for demethoxycurcumin and 0.0045-0.45 μg/mL for curcumin, respectively. In addition, the developed method provided low detection limits (0.1-0.4 ng/mL) and high enrichment factors (279-350). Its intra-day and inter-day precision were carried out by relative standard deviation ranged from 2.2% to 9.2%. Finally, the applicability of this method was assessed by the analysis of Curcumae Longae Rhizoma and turmeric tea samples. The results showed that these samples were detected successfully and the spiked recoveries over the range of 85.3%-108.9% with relative standard deviations 1.6%-8.9% were attained, indicating its high relative recoveries with good precision in real sample analysis. This article is protected by copyright. All rights reserved.

The Potential of Microextraction Techniques for the Analysis of Bioactive Compounds in Food

For a long time, the importance of sample preparation and extraction in the analytical performance of the most diverse methodologies have been neglected. Cumbersome techniques, involving high sample and solvent volumes have been gradually miniaturized from solid-phase and liquid-liquid extractions formats and microextractions approaches are becoming the standard in different fields of research. In this context, this review is devoted to the analysis of bioactive compounds in foods using different microextraction approaches reported in the literature since 2015. But microextraction also represents an opportunity to mitigate the environmental impact of organic solvents usage, as well as lab equipment. For this reason, in the recent literature, phenolics and alkaloids extraction from fruits, medicinal herbs, juices, and coffee using different miniaturized formats of solid-phase extraction and liquid-liquid microextraction are the most popular applications. However, more ambitious analytical limits are continuously being reported and emergent sorbents based on carbon nanotubes and magnetic nanoparticles will certainly contribute to this trend. Additionally, ionic liquids and deep eutectic solvents constitute already the most recent forefront of innovation, substituting organic solvents and further improving the current microextraction approaches.

Deep Eutectic Solvents as Promising Green Solvents in Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Droplet: Recent Applications, Challenges and Future Perspectives

Deep eutectic solvents (DESs) have recently attracted attention as a promising green alternative to conventional hazardous solvents by virtue of their simple preparation, low cost, and biodegradability. Even though the application of DESs in analytical chemistry is still in its early stages, the number of publications on this topic is growing. Analytical procedures applying dispersive liquid-liquid microextraction based on the solidification of floating organic droplets (DLLME-SFOD) are among the more appealing approaches where DESs have been found to be applicable. Herein, we provide a summary of the articles that are concerned with the application of DESs in the DLLME-SFOD of target analytes from diverse samples to provide up-to-date knowledge in this area. In addition, the major variables influencing enrichment efficiency and the microextraction mechanism are fully investigated and explained. Finally, the challenges and future perspectives of applying DESs in DLLME-SFOD are thoroughly discussed and are critically analyzed.

Ultrasound-assisted dispersive liquid-phase microextraction by solidifying L-menthol-decanoic acid hydrophobic deep eutectic solvents for detection of five fungicides in fruit juices and tea drinks

An ecofriendly and efficient ultrasound-assisted deep eutectic solvents dispersive liquid-phase microextraction by solidifying the deep eutectic solvents-rich phase was developed to determine azoxystrobin, fludioxonil, epoxiconazole, cyprodinil, and prochloraz in fruit juices and tea drinks by high-performance liquid chromatography. A varieties of environmental hydrophobic deep eutectic solvents serving as extraction agents were prepared using L-menthol and decanoic acid as hydrogen-bond acceptor and hydrogen-bond donor, respectively. The deep eutectic solvents were ultrasonically dispersed in sample solutions, solidified in a freezer and easily harvested. The main variables were optimized by one-factor-at-a-time and response surface test. The new method performs well with relative recovery of 71.75-109.40%, linear range of 2.5-5000 μg/L (r ≥ 0.9968), detection limit of 0.75-8.45 μg/L, quantification limit of 2.5-25 μg/L,_, and inter- and intraday relative standard deviations below 13.53 and 14.84%, respectively. As for the extraction mechanism, deep eutectic solvents were disposed into many fine particles in the solution and captured the analytes based on the changes of particle size and quantity in deep eutectic solvents droplets after extraction. The environmental method can successfully detect fungicide residues in real fruit juices and tea drinks.

Hydrophilic silicon nanoparticles as a turn-off and colorimetric fluorescent probe for curcuminoids detection in food samples and cell imaging

Hydrophilic fluorescent silicon nanoparticles (SiNPs) with good pH stability, salt-tolerance and anti-photobleaching were for the first time prepared from hydrophobic 3-glycidoxypropyltrimethoxysilane. Employing SiNPs as the fluorescence probe, selective quantification of curcuminoids based on the quenching effect was realized with a linearity of 0.046-7.4 μg/mL and a limit of detection of 17.6 ng/mL. Moreover, in light of fluorescence redshift of SiNPs corresponding to the elevated concentration of curcuminoids, a fluorescence colorimetric method was established based on only one extra probe, i.e. herein SiNPs. Thus, semi-quantification of curcuminoids (0-14.7 μg/mL) was visualized from blue to yellow color. Both the developed quantitative and semi-quantitative probe were successfully applied to determine curcuminoids in various actual food samples. Furthermore, SiNPs possessed low cytotoxicity and succeeded in intracellular curcuminoids imaging. The proposed SiNPs could be a promising fluorescence probe for multiple applications.

Extraction of phthalic acid esters from soft drinks and infusions by dispersive liquid-liquid microextraction based on the solidification of the floating organic drop using a menthol-based natural deep eutectic solvent

In this work, a natural deep eutectic solvent (NADES) consisting of L-menthol and acetic acid in a 1:1 molar ratio has been applied as extraction solvent for the dispersive liquid-liquid microextraction based on the solidification of the floating organic drop (DLLME-SFO) of a group of nine phthalic acid esters (dipropyl phthalate, DPP; butyl benzyl phthalate, BBP; dibutyl phthalate, DBP; dicyclohexyl phthalate, DCHP; diisopentyl phthalate, DIPP; di-n-pentyl phthalate, DNPP; di(2-ethylhexyl) phthalate, DEHP; diisononyl phthalate, DINP; and diisodecyl phthalate, DIDP) from three common infusions (camomile, pennyroyal mint, and linden teas) and three soft drinks (green tea, tonic, and lime and lemon drink), using dihexyl phthalate (DHP) and di-n-octyl phthalate (DNOP) as internal standards. After the DLLME-SFO procedure, analyses were carried out by high-performance liquid chromatography with UV detection. Method calibration showed good linearity for all the analytes and matrices, with determination coefficients (R²) higher than 0.9910. Relative recovery values were between 71 and 125 %, with relative standard deviation values in the range 1-22 % for the six types of samples, while the limits of quantification of the method were in the range 4.3-51.1 µg/L for infusions and in the range 3.5-33.3 µg/L for soft drinks. Several samples purchased in different local supermarkets were analysed, finding DPP, DBP, DIPP, DEHP and DINP, although only DPP, DBP and DEHP could be quantified in some of them.