Amino acids- based hydrophobic natural deep eutectic solvents as a green acceptor phase in two-phase hollow fiber-liquid microextraction for the determination of caffeic acid in coffee, green tea, and tomato samples

Natural deep eutectic solvent for the simultaneous derivatization and microextraction of isoniazid from human plasma

BACKGROUND

Personalized medicine is a rapidly revolving field that offers new opportunities for tailoring disease treatment to individual patients. The main idea behind this approach is to carefully select safe and effective medications and treatment plant based on each patient's unique pharmacokinetic profile. Isoniazid is a first-line anti-tuberculosis drug that has interindividual variability in its metabolic processing, leading to significant differences in plasma concentrations among patients receiving equivalent doses. This variability necessitates the creation of individualized treatment regimens as part of personalized medicine to achieve more effective therapy.

RESULTS

In this work, a deep eutectic solvent-based liquid-liquid microextraction approach for the separation and determination of isoniazid in human plasma by high-performance liquid chromatography with UV-Vis detection was developed for the first time. A new natural deep eutectic solvent based on thymol as a hydrogen bond donor and 4-methoxybenzaldehyde as a hydrogen bond acceptor was proposed as the extraction solvent. The developed microextraction procedure assumed two simultaneous processes during the mixing of the sample and extraction solvent: the derivatization of the polar analyte in the presence of 4-methoxybenzaldehyde (component of the natural deep eutectic solvent) with the formation of a hydrophobic Schiff base (1); mass transfer of the Schiff base from the sample phase to the extraction solvent phase (2). Under optimal conditions, the limits of detection and quantification were 20 and 60 μg L-1, respectively. The RSD value was <10 %, the extraction recovery was 95 %.

SIGNIFICANCE

In this work, the possibility of isoniazid derivatization in the natural deep eutectic solvent phase with the formation of the Schiff base was presented for the first time. The approach provided the separation and preconcentration of polar isoniazid without the use of expensive derivatization agents and solid-phase extraction cartridges. The formation of the Schiff base was confirmed by mass spectrometry.

Comparison of Physicochemical, Antioxidant, and Cytotoxic Properties of Caffeic Acid Conjugates

Spectroscopic studies (FT-IR, Raman, 1H, and 13C NMR, UV-VIS) of caffeic acid (CFA) and its conjugates, i.e., caftaric acid (CTA), cichoric acid (CA), and cynarin (CY), were carried out. The antioxidant activity of these compounds was determined by a superoxide dismutase (SOD) activity assay and the hydroxyl radical (HO•) inhibition assay. The cytotoxicity of these compounds was performed on DLD-1 cell lines. The molecules were theoretically modeled using the B3LYP-6-311++G(d,p) method. Aromaticity indexes (HOMA, I6, BAC, Aj), HOMO and LUMO orbital energies and reactivity descriptors, NBO electron charge distribution, EPS electrostatic potential maps, and theoretical IR and NMR spectra were calculated for the optimized model systems. The structural features of these compounds were discussed in terms of their biological activities.

In situ formation of natural deep eutectic solvent on membrane after fat hydrolysis for lindane isomers determination in peanut paste

In this work a sample pretreatment approach assumed liquid-liquid microextraction based on the in situ formation of a hydrophobic natural deep eutectic solvent on a hydrophobic membrane impregnated with natural terpenoid was developed. The procedure included alkaline hydrolysis of a food sample containing fat to form fatty acids, which acted as precursors for the in situ formation of the deep eutectic solvent with natural terpenoid. Two processes were observed on the membrane surface: in situ formation of the hydrophobic deep eutectic solvent and liquid-liquid microextraction of the target analytes. After microextraction, the membrane containing the analytes was easily removed from the sample solution. The developed approach was applied to the separation and preconcentration of hydrophobic organochlorine pesticides (ɑ-hexachlorocyclohexane and γ-hexachlorocyclohexane) from a hydrophobic sample matrix (peanut paste), followed by their determination by gas chromatography with electron capture detection. Under optimal conditions, the limits of detection and quantification for both analytes were 0.3 and 1.0 μg kg-1, respectively. The procedure allowed the separation of fat-soluble analytes from a complex sample matrix with a high content of fat. The extraction recoveries were in the range of 93-95 %.

Selective extraction of plant bioactive compounds with deep eutectic solvents: Iris sibirica L. as example

INTRODUCTION

Deep eutectic solvents (DESs) are promising extractants with tuneable properties. However, there is a lack of reports about the influence of the nature of the original DES on obtaining the metabolomic profile of a plant.

OBJECTIVE

The aim of this study is to investigate the possibility of obtaining Iris sibirica L. chromatographical profiles with DESs based on various hydrogen bond donors and acceptors as extraction solvents.

METHODOLOGY

DESs were prepared by mixing choline chloride or tetrabutylammonium bromide with various hydrogen bond donors and investigated for the extraction of bioactive substances from biotechnological raw materials of I. sibirica L. The obtained extracts were analysed by HPLC with diode array detector (DAD) and Q-MS.

RESULTS

Chromatographic profiles for I. sibirica L. extracts by eight choline chloride DESs and six tetrabutylammonium DESs have been obtained. It has been found that selective recovery of bioactive substances can be achieved by varying the composition of DESs. Eleven phenolic compounds were identified in I. sibirica L. using HPLC-MS. Phase separation was observed with acetonitrile for four DESs. New flavonoid derivatives have been found in DES extracts compared with methanol extracts.

CONCLUSION

The results showed the possibility of DES usage for extraction without water addition. Selectivity of DESs varies depending on the chemical composition of hydrogen bond donors and acceptors. Choline chloride is a more suitable hydrogen bond acceptor for the flavonoid extraction. Choline chloride-lactic acid (1:1) DES has demonstrated a metabolic profile that was the closest to the methanol one and enhanced the extraction up to 2.6-fold.

Applications of deep eutectic solvents in microextraction and chromatographic separation techniques: Latest developments, challenges, and prospects

Deep eutectic solvents (DESs) have recently sparked considerable attention in a variety of scientific and technological fields. The unique properties of DESs include biodegradability, easy preparation, low cost, and tuneability, rendering them a new and prospective alternative to hazardous solvents. Analytical chemistry is one of the most appealing fields where DESs proved to be applicable in either sample preparation or chromatographic separation. This review summarizes the new horizons dedicated to the application of DESs in microextraction and chromatographic separation. The utilization of DESs in microextraction, in chromatography as mobile phase additives, and in chromatographic material preparation processes is outlined. The enhancements in chromatographic performance achieved using DESs and any potential explanations deduced from the experimental findings were primarily discussed. An additional brief discussion on DESs preparation, characterization, and properties is addressed in this work. Finally, current challenges and future trends are also presented, supplying evidence for distinct possibilities regarding new research approaches involving DESs. This review can represent a guide and stimulate further research in this field.

Preparation of Ferrofluid from Adipic Acid Coated Magnetic Nanoparticles and Hydrophobic Deep Eutectic Solvent Used in Dispersive Micro-Solid-Phase Extraction: Application for the Pre-Concentration and Determination of Clozapine in Biological Samples

The aim of the present study is the preparation of a novel magnetic ferrofluid (FF) based on a hydrophobic deep eutectic solvent (DES), which is used for the extraction of trace quantities of clozapine from biological samples. For this purpose, a highly stable FF was prepared through the combination of adipic acid-coated magnetic nanoparticles (MNPs) plus tetraethylammonium chloride/thymol hDES without an additional stabilizer. These solvents were synthesized by the available and less-toxic materials, which is the appropriate option to support the solvents for the preparation of FF. In this study, a water-immiscible DES acts simultaneously as a carrier and stabilizer for the MNPs. In addition, the strong interactions between clozapine and magnetic FF could increase the extraction efficiency. The fractional factorial design was used for screening the experimental parameters. Then, the effective factors were optimized using the Box-Behnken design. The optimum extraction conditions were the following: pH of the sample solution: 8, the volume of the desorption solvent: 200 μL and desorption time: 5 min. Moreover, the suggested method exhibited low limits of detection in the range of 2.8-3.1 μg L-1. The linear range was 10.0-500.0 μg L-1 for human plasma and urine samples with acceptable recoveries greater than 91.4%. In addition, the proposed method is convenient, sensitive, effective, rapid and environmentally friendly.

Mechanistic insights into the lignin dissolution behavior in amino acid based deep eutectic solvents

Deep eutectic solvents (DESs) composed by amino acids (L-arginine, L-proline, L-alanine) as the hydrogen bond acceptors (HBAs) and carboxylic acids (formic acid, acetic acid, lactic acid, levulinic acid) as hydrogen bond donors (HBDs) were prepared and used for the dissolution of dealkaline lignin (DAL). The mechanism of lignin dissolution in DESs was explored at molecular level by combining the analysis of Kamlet-Taft (K-T) solvatochromic parameters, FTIR spectrum and density functional theory (DFT) calculations of DESs. Firstly, it was found that the formation of new hydrogen bonds between lignin and DESs mainly drove the dissolution of lignin, which were accompanied by the erosion of hydrogen bond networks in both lignin and DESs. The nature of hydrogen bond network within DESs was fundamentally determined by the type and number of functional groups in both HBA and HBD, which affected its ability to form hydrogen bond with lignin. One hydroxyl group and carboxyl group in HBDs provided active protons, which facilitated proton-catalyzed cleavage of β-O-4, thus enhancing the dissolution of DESs. The superfluous functional group resulted in more extensive and stronger hydrogen bond network in the DESs, thus decreasing the lignin dissolving ability. Moreover, it was found that lignin solubility had a closed positive correlation with the subtraction value of α and β (net hydrogen donating ability) of DESs. Among all the investigated DESs, L-alanine/formic acid (1:3) with the strong hydrogen-bond donating ability (acidity), weak hydrogen-bond accepting ability (basicity) and small steric-hindrance effect showed the best lignin dissolving ability (23.99 wt%, 60 °C). On top of that, the value of α and β of L-proline/carboxylic acids DESs showed some positive correlation with the global electrostatic potential (ESP) maxima and minima of the corresponding DESs respectively, indicating the analysis of ESP quantitative distributions of DESs could be an effective tool for DESs screening and design for lignin dissolution as well as other applications.

Hydrophobic Deep Eutectic Solvents as Greener Substitutes for Conventional Extraction Media: Examples and Techniques

Deep eutectic solvents (DESs) are multicomponent designer solvents that exist as stable liquids over a wide range of temperatures. Over the last two decades, research has been dedicated to developing noncytotoxic, biodegradable, and biocompatible DESs to replace commercially available toxic organic solvents. However, most of the DESs formulated until now are hydrophilic and disintegrate via dissolution on coming in contact with the aqueous phase. To expand the repertoire of DESs as green solvents, hydrophobic DESs (HDESs) were prepared as an alternative. The hydrophobicity is a consequence of the constituents and can be modified according to the nature of the application. Due to their immiscibility, HDESs induce phase segregation in an aqueous solution and thus can be utilized as an extracting medium for a multitude of compounds. Here, we review literature reporting the usage of HDESs for the extraction of various organic compounds and metal ions from aqueous solutions and absorption of gases like CO₂. We also discuss the techniques currently employed in the extraction processes. We have delineated the limitations that might reduce the applicability of these solvents and also discussed examples of how DESs behave as reaction media. Our review presents the possibility of HDESs being used as substitutes for conventional organic solvents.

Pressurized natural deep eutectic solvents: An alternative approach to agro-soy by-products

Soybeans are mainly used for food and biodiesel production. It is estimated that soy crops worldwide will leave about 651 million metric tons of branches, leaves, pods, and roots on the ground post-harvesting in 2022/23. These by-products might serve as largely available and cheap source of high added-value metabolites, such as flavonoids, isoflavonoids, and other phenolic compounds. This work aimed to explore green approaches based on the use of pressurized and gas expanded-liquid extraction combined with natural deep eutectic solvents (NADESs) to achieve phenolic-rich extracts from soy by-products. The total phenolic and flavonoid contents of the generated extracts were quantified and compared with conventional solvents and techniques. Pressurized liquid extraction (PLE) with choline chloride/citric acid/water (1:1:11 – molar ratio) at 120°C, 100 bar, and 20 min, resulted in an optimized condition to generate phenolic and flavonoid-rich fractions of soy by-products. The individual parts of soy were extracted under these conditions, with their metabolic profile obtained by UHPLC-ESI-QToF-MS/MS and potential antioxidant properties by ROS scavenging capacity. Extracts of soy roots presented the highest antioxidant capacity (207.48 ± 40.23 mg AA/g), three times higher than soybean extracts (68.96 ± 12.30). Furthermore, Hansen solubility parameters (HSPs) were applied to select natural hydrophobic deep eutectic solvents (NaHDES) as substituents for n-heptane to defat soybeans. Extractions applying NaHDES candidates achieved a similar yield and chromatography profile (GC-QToF-MS) to n-heptane extracts.

In-syringe solid phase extraction and in-syringe vortex-assisted solidified floating organic drop microextraction of Sb(III) and Sb(V) in rice wines with determination by graphite furnace atomic absorption spectrometry

The current non-chromatographic speciation methods generally involve the conversion of different species by oxidation/reduction reactions, which may cause inherent problems such as contamination risk, time consumption and complex operations. In this work, in-syringe solid phase extraction (IS-SPE) was combined with in-syringe vortex-assisted solidified floating organic drop microextraction (IS-VA-SFODME) for the detection of Sb(V) and Sb(III) in rice wines by graphite furnace atomic absorption spectrometry. Firstly, IS-SPE involved the use of ZnFe₂O₄ nanotubes as the sorbent for the isolation and enrichment of Sb(V) and removal of the matrix components such as ethanol, pigment, sugars and carbohydrates. Then, IS-VA-SFODME was used for enriching Sb(III) in the original sample solution after IS-SPE. This technique exhibited good anti-interference ability and high enrichment efficiency without tedious pre-oxidation/pre-reduction and centrifugation/filtration operations, which may cause the contamination of samples. Under the selected conditions, the detection limits were 4.5 ng L^-1 and 3.2 ng L^-1 for Sb(III) and Sb(V) with relative standard deviations of 7.3% and 5.1%, respectively. This procedure was used with satisfactory results for the detection of Sb(III) and Sb(V) in rice wine samples and a certified reference material of water sample. Recoveries of spiked experiments ranged from 91.0 to 107%.

Liquid-Phase Microextraction Approaches for Preconcentration and Analysis of Chiral Compounds: A Review on Current Advances

Chirality is a critical issue in pharmaceutics, forensic chemistry, therapeutic drug monitoring, doping control, toxicology, or environmental investigations as enantiomers of a chiral compound can exhibit different activities, i.e., one enantiomer can have the desired effect while the other one can be inactive or even toxic. To monitor enantioselective metabolism or toxicokinetic/toxicodynamic mechanisms in extremely low content in biological or environmental matrices, sample preparation is vital. The present review describes current status of development of liquid-phase microextraction approaches such as hollow fiber liquid-phase microextraction (HF-LPME), electromembrane extraction (EME), dispersive liquid-liquid microextraction (DLLME), and supramolecular solvent-based microextraction (SSME), used for sample preparation of enantiomers/chiral compounds. The advantages and limitations of the above techniques are discussed. Attention is also focused on chiral separation approaches commonly applied to study the stereo-selective metabolism or toxicokinetic/toxicodynamic mechanisms of enantiomers in the biological and environmental samples.

Latest Insights on Novel Deep Eutectic Solvents (DES) for Sustainable Extraction of Phenolic Compounds from Natural Sources

Phenolic compounds have long been of great importance in the pharmaceutical, food, and cosmetic industries. Unfortunately, conventional extraction procedures have a high cost and are time consuming, and the solvents used can represent a safety risk for operators, consumers, and the environment. Deep eutectic solvents (DESs) are green alternatives for extraction processes, given their low or non-toxicity, biodegradability, and reusability. This review discusses the latest research (in the last two years) employing DESs for phenolic extraction, solvent components, extraction yields, extraction method characteristics, and reviewing the phenolic sources (natural products, by-products, wastes, etc.). This work also analyzes and discusses the most relevant DES-based studies for phenolic extraction from natural sources, their extraction strategies using DESs, their molecular mechanisms, and potential applications.

Automated liquid-liquid microextraction and determination of sulfonamides in urine samples based on Schiff bases formation in natural deep eutectic solvent media

In this work, an automated liquid-liquid microextraction procedure for the determination of sulfonamides (sulfamethoxazole, sulfamethazine and sulfapyridine) in urine samples using natural deep eutectic solvent is presented for the first time. The mechanism for extraction of sulfonamides was based on the formation of colored Schiff bases in the presence of vanillin, which acted as a derivatization reagent and precursor of natural deep eutectic solvent (an extractant). In this procedure, thymol was used as both media for Schiff bases formation and as a second precursor of the natural deep eutectic solvent. The formation of the Schiff bases was confirmed by mass spectrometry. A Lab-In-Syringe concept was applied for the automation of the microextraction procedure. The procedure involved mixing the sample and natural deep eutectic solvent into a syringe of a flow system, formation and microextraction of colored Schiff base followed by UV-Vis detection. Under optimal automated conditions the limits of detection, calculated from a blank test based on 3s (sigma) were 0.06, 0.1, and 0.06 mg L^-1 for sulfapyridine, sulfamethoxazole and sulfamethazine. The proposed automated procedure permitted the routine determination of one drug (sulfamethoxazole, sulfamethazine or sulfapyridine) in urine samples to be achieved in less than 10 min.