Hydrophobic Solvents Research Articles

Non-Toxic Natural Additives to Improve the Electrical Conductivity and Viscosity of Polycaprolactone for Melt Electrospinning

Polycaprolactone (PCL) is biodegradable and non-toxic, making it an eco-friendly polymer with various medical applications. In order to increase the stability of PCL used in the field of medical applications, it is necessary to be able to produce fibers with a melt electrospinning method that does not use toxic hydrophobic solvents. However, PCL has very high viscosity and low conductivity, making melt electrospinning difficult. This study presents natural additives enabling the solvent-free melt electrospinning of PCL, wherein the physical properties (i.e., conductivity and viscosity) of the additive-mixed PCL are analyzed. Among the natural additives added to PCL, 7 wt% gallic acid increased conductivity by 81 times and decreased viscosity by 1/8526 times, showing the best results. We believe that our study, improving the physical properties of melt PCL by adding natural additives, will be of great help to the development of the melt electrospinning method of PCL.

Hydrophobic Deep eutectic Solvents based on cineole and organic acids

The hydrophobic Natural Deep Eutectic Solvent formed by the combination of cineole and decanoic acid (capric acid) was studied using a combined experimental and computational approach. Experimental study was carried considering relevant physicochemical properties as density, viscosity, refraction index and thermal conductivity as a function of temperature, as well as Raman spectra for 785 nm excitation wavelength. Thermophysical properties measured showed a low -viscous low-dense fluid, which is of great relevance for its technological application, as well as the Raman spectra confirmed the formation of hydrogen bonding. The analysis of nanoscopic properties and structuring was carried out using theoretical method as the Density Functional Theory (BP86/def2-TZVP plus Grimme’s D3 theoretical level) and classical Molecular Dynamics simulation (using AMOEBA polarizable force field). Molecular modelling studies using quantum chemistry and classical molecular dynamics methods allowed a nanoscopic characterization of the fluid as well as of its intermolecular forces (hydrogen bonding). Phase equilibria were predicted using COSMO method considered solid–liquid (melting behavior) and vapor – liquid (evaporation), as well as excess properties. The COSMO results showed a low volatile, wide liquid range fluid, characterized by non-ideality because of the formation of hydrogen bonding. Likewise, the interaction of the considered material with POPC lipid was studied using COSMOperm method to analyze its behavior at lipid bilayers as models of cell membranes for the consideration of its possible toxicological effects, showing how the considered molecules are able to penetrate and disrupt the model membranes because of the lipophilic nature of the considered molecules.

Structural evolution of the butylated hydroxytoluene/menthol hydrophobic eutectic solvent upon methanol and ethanol cosolvent addition

The changes upon methanol (MeOH) and ethanol (EtOH) addition in the structural arrangement of the hydrophobic eutectic solvent formed by butylated hydroxytoluene (BHT) and L-menthol (MEN) in 1:3 M ratio have been studied using molecular dynamics (MD) simulations integrated by small- and wide-angle X-ray scattering (SWAXS) measurements. Different mixtures containing the eutectic solvent and a variable amount of MeOH and EtOH have been investigated and the cosolvent introduction at any concentration has been found to break the hydrogen-bonds (H-bonds) among the MEN molecules, that are the most relevant interactions in the pristine eutectic, while the BHT component remains substantially non-interacting through all the explored composition range. This H-bond network is replaced by interactions between the MEN component and the cosolvent molecules, where the MEN species acts preferentially as H-bond donor towards the MeOH and EtOH molecules that behave mostly as H-bond acceptors. An increasing interplay between the excess cosolvent molecules is also observed upon increasing their concentration. SWAXS data show a contraction of the electron-dense regions corresponding to the hydroxyl groups upon cosolvent addition. This evidence is compatible with the intercalation of the MeOH and EtOH molecules in the MEN-MEN H-bond network to promote MEN-cosolvent and cosolvent-cosolvent interactions, in agreement with the MD results.

Ultrasonic-assisted hydrophobic deep eutectic solvents for the extraction of seven compounds from Piperis longi fructus-Rhei radix et rhizoma drug pair and their vitro antioxidant evaluation

Deep eutectic solvents have become an alternative to organic solvents due to their unique advantages and are widely used in the extraction of traditional Chinese medicine. In this study, a new green ultrasound-assisted extraction technique based on hydrophobic deep eutectic solvents was developed and applied to the extraction of seven compounds from Piperis longi fructus-Rhei radix et rhizoma drug pair. The key factors affecting the extraction efficiency were systematically investigated by single factor experiments: molar ratio, liquid/solid ratio, vortex time, extraction time and temperature. The parameters of the extraction process after optimization using the response surface method were molar ratio 1:2.4, extraction time 40 min, liquid/solid ratio 22:1 mL/g. In order to gain insight into the superiority of hydrophobic deep eutectic solvents in the extraction, a principal component analysis was performed. The results show that the hydrophobic deep eutectic solvent, consisting of fatty acids and long chain alkanols, has a wide range of extraction polarity and high extraction efficiency compared to methanol. The infrared spectra showed the formation of hydrogen bonds between the deep eutectic solvents, which may be the reason why hydrophobic deep eutectic solvents are potential extraction solvents. Furthermore, the extracts of hydrophobic deep eutectic solvents showed satisfactory free radical scavenging activity. The results obtained from the study proved that the method is efficient and feasible, which could help further the application of hydrophobic deep eutectic solvents for the extraction of weakly polar active compounds in Chinese medicine.

Decontamination of enoxacin containing aqueous phase through hydrophobic deep eutectic solvents: Solvent regeneration and quantum chemical insights

The current work addresses the extraction of a drug (enoxacin) from an aqueous environment by liquid-liquid extraction using three hydrophobic deep eutectic solvents (DES) namely, (a) dl-menthol: decanoic acid (1:1), (b) dl-menthol: dodecanoic acid (2:1), and (c) dodecanoic acid: decanoic acid (1:2). The experiments were conducted at varying mass ratios of DES/ water phase at ambient condition followed by quantum chemical (QC) analysis. Within the batch process with a single cycle, the extraction efficiency and the distribution ratio of 82 % and 4.75 respectively, were reported with the DES; dl-menthol: decanoic acid (1:1). Different initial drug concentrations (5 to 20 ppm) were introduced to observe the extraction performance at various contamination levels. Followed by the batch-type extraction experiments, three different recycling schemes have been implemented to assess the reuse and recovery of DESs. A 90 % percentage extraction was achieved by recycling the DES phase with purification through activated carbon (AC) which allowed it to maintain its continuity of the aqueous phase. The higher hydrophobicity of the DES phase with relatively high drug solubility proved to be the driving force of the enhanced DES-drug interaction. This was supported by the QC analysis as comparably higher non-bonded interaction energy was obtained for the DES-enoxacin complex suggesting stronger interaction and compactness. The charge transfer (CT) process confirmed the magnitude of charge transfer between DES and the drug through natural bonding orbital (NBO) charge analysis. Non-bonded interactions with dispersion effect were confirmed by the structural arrangement analysis of the complex supported by frontier molecular orbital (FMO) analysis. The quantum theory of atom in molecules and the non covalent interaction (QTAIM & NCI) analysis suggest hydrogen bonding and dispersion interactions (van der Waals) as the basis of interaction between the molecular groups.

CO2-Responsive Hydrophobic Deep Eutectic Solvent Based on Surfactant-Free Microemulsion-Mediated Synthesis of BaF2 Nanoparticles.

A new form of surfactant-free microemulsion (SFME) including hydrophobic deep eutectic solvent (HDES)/ethanol/water was constructed based on its CO2 response, and three regions, that is, HDES-in-water (HDES/W), bicontinuous (B.C.), and water-in-HDES (W/HDES) regions, were recognized. It is anticipated that SFMEs with tunable microstructures have outstanding applications as nanoreactors in reaction processes. The feasibility of preparing nanoparticles from HDES/ethanol/water SFME using barium fluoride (BaF2) as a model nanoparticle was investigated. HDES-based microemulsions benefit from HDES's excellent properties (novel, low toxicity, CO2-responsive, easy availability) and have potential in universal reactions, drug delivery, advanced material fabrication, etc. In this research, HDES-based microemulsions were prepared using HDES as the oil phase. Phase equilibria and microstructure were investigated using a ternary phase diagram, UV spectrophotometry, and the conductivity method. The CO2 switchable characteristics of the HDES-based microemulsions were investigated. HDES-based microemulsions were proposed as nanoreactors for the synthesis of barium fluoride nanomaterials. The microemulsion structure can modulate the size, morphology, and physicochemical properties of the nanoparticles through the CO2 switchable properties. It is argued that nanoreactors constructed with versatile HDES will offer a new direction for creation of cutting-edge scientific applications.

Phase separation‐induced nanoprecipitation for making polymer nanoparticles with high drug loading

AbstractIncreasing drug loading remains a critical challenge in the development and translation of nanomedicine. High drug‐loading nanoparticles have demonstrated unique advantages such as less carrier material used, better‐controlled drug release, and improved efficacy and safety. Herein, we report a simple and efficient salt concentration screening method for making polymer nanoparticles with exceptionally high drug loading (up to 66.5 wt%) based on phase separation‐induced nanoprecipitation. Upon addition of salt, phase separation occurs in a miscible solvent‐water solution delaying the precipitation time of drugs and polymers to different extents, facilitating their co‐precipitation thus the formation of high drug‐loading nanoparticles with high encapsulation efficiency (>90%) and excellent stability (>1 month). This technology is versatile and easy to be adapted to various hydrophobic drugs, different polymers, and solvents. This salt‐induced nanoprecipitation strategy offers a novel approach to fabricating polymer nanoparticles with tunable drug loading, and opens great potentials for future nanomedicines.

Extraction of Ursolic Acid from Apple Peel with Hydrophobic Deep Eutectic Solvents: Comparison between Response Surface Methodology and Artificial Neural Networks.

Extracting ursolic acid (UA) from plant resources using organic solvents is incompatible with food applications. To address this, in this study, 15 edible hydrophobic deep eutectic solvents (HDESs) were prepared to extract UA from apple peel, the extraction conditions were optimized, and the optimization strategies were compared. It was found that the solubility of UA in the HDESs can be 9 times higher than the traditional solvent such as ethanol. The response surface optimization concluded that temperature had the greatest effect on the extraction and the optimized test conditions obtained as follows: temperature of 49 °C, time of 32 min, solid-liquid ratio of 1:16.5 g/mL, respectively. Comparing the response surface methodology (RSM) and artificial neural networks (ANN), it was concluded that ANN has more accurate prediction ability than RSM. Overall, the HDESs are more effective and environmentally friendly than conventional organic solvents to extract UA. The results of this study will facilitate the further exploration of HDES in various food and pharmaceutical applications.

Experimental study on CO2 separation using hydrophobic deep eutectic solvent based supported liquid membranes

Deep eutectic solvents (DESs) have been proposed as a viable and more sustainable solvent for CO2 capture, owing to their low volatility and tunable properties. In this work, polymer membranes were combined with hydrophobic DESs to prepare supported liquid membranes (DES-SLMs), and the potential of using SLMs for CO2/N2 separation was investigated. COSMO-RS model simulations, bond energy analysis as well as stability tests were used to select the polymeric porous support. Hydrophobic polyvinylidene fluoride (PVDF) with a nominal pore size of 0.1 μm was chosen to support three selected hydrophobic DESs. The gas permeabilities through three selected DES-SLMs were experimentally determined, where the thymol-coumarin (1:1) based SLM showed the best performance with a CO2 permeability of 175.0 Barrer and selectivity of 30.2 at room temperature. The separation capability was further improved by mixing the DES with traditional physical absorbents. In addition, the effects of water presence in the gas phase on the DES-SLM were investigated. The membrane was physically stable, but the ideal selectivity of CO2/N2 through the membrane deteriorated with time on steam. By predicting the permeabilities of CO2 and N2 through traditional organic liquid based SLMs, the prospects of developing DESs for SLM applications were demonstrated. Finally, an advanced membrane capture process for a natural gas-fired combined cycle (NGCC) power plant was studied with process simulation and economic analysis, where the SLMs are used to purify the CO2 product.

Sustainable recovery of phenolic antioxidants from real olive vegetation water with natural hydrophobic eutectic solvents and terpenoids

Olive oil production leads to the generation of olive mill wastewater (OMWW). Due to the presence of phenolic compounds, they are difficult to process, but they represent a source of high-added value chemicals since they have antioxidant and therapeutic properties. This work has studied the extraction of phenolic compounds from a type of OMWW, olive vegetation water, which presents these compounds in a more diluted dosage than in other studied to date, to revalue this waste stream. A real olive vegetation water from a Spanish olive oil producer was used, and liquid-liquid extraction was applied. Terpenoids and terpene-based hydrophobic eutectic solvents were systematically used to extract phenolic compounds following the concentrations of tyrosol, catechol, caffeic acid, and total phenolic content. By molecular simulation with the COSMO-RS method, 4 terpenoids, and 2 eutectic solvents were selected and compared with 2 conventional solvents. The Solvent/Feed ratio in the extraction of phenolic compounds was studied, showing that the solvents with the highest extraction results were geraniol, eucalyptol, and eutectic solvent menthol + camphor, which outperformed conventional solvents methyl isobutyl ketone and diisopropyl ether. Menthol + camphor gave total phenol extraction yields of 88.73% at a Solvent/Feed ratio in volume of 0.50, surpassing all solvents tested. A solvent reuse and regeneration process was applied by back-extraction of the 4 solvents: FTIR results showed the stability of the solvents while maintaining yields in the solvent reuse process. The phenolic compounds could be concentrated in the alkaline phase to factors up to 49.3 to the initial concentration in olive vegetation water. The alkaline phases were neutralized to obtain a precipitate with a caffeic acid content of up to 26 % wt%, and a tyrosol-rich supernatant with a concentration of up to 6.54 g/L. This work proposes a process using natural solvents to extract phenolic compounds from olive vegetation water.

Sustainable solutions for removing aged wax-based coatings from cultural heritage: exploiting hydrophobic deep eutectic solvents (DESs)

Hydrophobic deep eutectic solvents as suitable alternatives to toxic solvents used in the conservation of Cultural Heritage sector.

Origin of structural and dynamic heterogeneity in thymol and coumarin-based hydrophobic deep eutectic solvents as revealed by molecular dynamics.

Hydrophobic deep eutectic solvents (HDESs) have recently emerged as a class of water-immiscible solvents with greener starting materials and inherent hydrophobic character, opening the gates to various new promising applications. Herein, we have carried out all-atom molecular dynamics simulations to comprehend the bulk phase structural organization and dynamic behavior of thymol and coumarin-based HDESs at two molar ratios of the constituent components. The simulated X-ray and neutron scattering structure functions (S(q)s) indicate a prepeak signifying that these HDESs possess nanoscale heterogeneity or intermediate range ordering. The decomposition of the total S(q)s based on polarity reveals that clustering of the polar group present in thymol and coumarin leads to the presence of the prepeak which also has small contributions from the apolar-apolar correlations. The intermolecular hydrogen bonding network between thymol-coumarin and thymol-thymol mainly guides the arrangement of the HDESs. We find a stronger hydrogen bond between the carbonyl oxygen of coumarin and the hydroxyl hydrogen of thymol, marked by the longer hydrogen bond lifetime. In contrast, the shorter lifetime of the hydrogen bond between the hydroxyl oxygen and the hydroxyl hydrogen of thymol suggests a weaker hydrogen bonding. On changing the thymol : coumarin molar ratio from 1 : 1 to 2 : 1, the average lifetimes of both the hydrogen bonds decrease, suggesting stronger hydrogen bonds in the 1 : 1 HDES. The translational dynamics of thymol and coumarin become faster in the 2 : 1 thymol : coumarin HDES. A slightly stronger caging effect is observed for coumarin in comparison to thymol molecules. From the analysis of the non-Gaussian parameter, we observe the presence of heterogeneity in the translational displacements of thymol and coumarin molecules. Furthermore, the computed self-van Hove correlation functions reveal that thymol and coumarin molecules cover more distances than the ideal diffusive displacements, confirming the presence of dynamic heterogeneity.

Extraction and determination of aflatoxin B1 in cereal samples using pH-switchable hydrophobic deep eutectic solvents followed by HPLC-FL analysis.

A quick, simple and environmentally friendly liquid phase microextraction (LPME) sample pretreatment procedure was proposed based on pH-switchable hydrophobic deep eutectic solvents (HDESs) and high performance liquid chromatography coupled with a fluorescence detector (HPLC-FL). This method was used for the quantitative study of aflatoxin B1 (AFB1) and applied to eight widely consumed cereal samples. In this method, six different DESs were synthesized and then their pH-switchability was investigated. DESs that could be switched with pH were employed for separation and preconcentration of AFB1 in cereal samples. In this method, dispersing the extractant phase in the aqueous solution and subsequent phase separation are performed only by changing the pH. Important parameters affecting extraction, such as the type of DES and its volume, concentration of KOH, volume of HCL, effect of salt and extraction time were investigated and optimum conditions were obtained. Under the optimum conditions, relative standard deviation (RSD) values for intra-day and inter-day of the method based on seven replicate measurements of 5.0 μg kg-1 of AFB1 in cereal samples were 3.3 and 5.2%, respectively. The calibration graphs were linear in the range of 0.007-20 μg kg-1 and limit of detection (LOD) was 0.002 μg kg-1. The relative recoveries of real cereal samples which have been spiked with different levels of AFB1 were 90.8-107.5%.

A novel microextraction technique aided by air agitation using a natural hydrophobic deep eutectic solvent for the extraction of fluvastatin and empagliflozin from plasma samples: application to pharmacokinetic and drug-drug interaction study.

This study focuses on the interaction between the antihyperlipidemic drug fluvastatin (FLV) and the antidiabetic drug empagliflozin (EMP), which are commonly co-administered medications. EMP's impact on FLV levels is attributed to its inhibition of organic anion transporting polypeptide 1B1 (OATP1B1), responsible for FLV liver uptake, consequently elevating FLV concentrations in blood. Traditional extraction methods for FLV faced difficulties due to its high hydrophobicity. In this study, a hydrophobic natural deep eutectic solvent (NDES) using air assisted dispersive liquid-liquid microextraction (AA-DLLME) was utilized as an excellent choice for achieving the highest extraction recovery, reaching 96% for FLV and 92% for EMP. The NDES was created through the combination of menthol and hippuric acid in a 4 : 1 ratio, making it a green and cost-effective pathway. Liquid phase microextraction followed by spectrofluorometric measurements of FLV at λem = 395 nm and EMP at λem = 303 nm, with excitation at a single wavelength of 275 nm was carried out. Response surface methodology (RSM) relying on central composite design (CCD) was used to optimize the variables affecting the AA-NDES-DLLME. The optimized conditions for extraction are: NDES volume of 200 μL, centrifugation time of 15 minutes, air-agitation cycle of 6 cycles, and sample pH of 4.0. Under these optimized conditions, the developed method exhibited good linearity and precision. The method showed good recoveries from rabbit plasma samples spiked at varying concentrations of the analyzed compounds. To assess the applicability and effectiveness of the hydrophobic DES, the validated method was applied to extract the studied drugs from rabbit plasma samples after oral administration of FLV alone and in combination with EMP. The pharmacokinetic parameters of FLV were calculated in both cases to investigate any changes and determine the need for dose adjustment.

Dioctyl sodium sulfosuccinate surfactant self-assembly dependency of solvent hydrophilicity: a modelling study.

The self-assembly of dioctyl sodium sulfosuccinate (AOT) model surfactant in solvent environments of differing polarity is examined by means of dissipative particle dynamics (DPD) bead model parametrized against Hildebrand solubility parameters from atomistic molecular dynamics (MD) simulations. The model predicts that in hydrophobic solvents (e.g. dodecane) the surfactant forms small (Nagg ∼ 8) reverse micellar aggregates, while in a solvent corresponding to water lamellar assembly takes place, in good agreement with literature structural parameters. Interestingly, solvents of intermediate polarity lead to formation of large, internally structured aggregates. In these, the surfactant headgroups cluster within the aggregate, surrounded by a continuous phase formed by the hydrocarbon tails. We show that the partitioning of the headgroups between the aggregate surface layer and the inner clustered phase depends primarily on solvent polarity, and can be controlled by the solvent, but also system composition. Finally, we compare the DPD assembly response to simplified effective interaction potentials derived at dilute concentration limit for the interactions. The comparison reveals that the simplified effective potential descriptions provide good level of insight on the assembly morphologies, despite drastic, isotropic interactions simplification involved.

Evaluation of terpene-based hydrophobic deep eutectic solvents as skin permeation enhancers

We investigated whether carboxylic acid-terpene-based deep eutectic solvents (DESs) can be used as skin permeation enhancers. We performed transdermal experiments, and their results showed that DESs with longer hydrocarbon chains can enhance the skin permeability of hydrophilic fluorescein sodium and hydrophobic meloxicam. Additionally, all DESs could improve the skin permeability of poorly soluble resveratrol. Subsequently, we evaluated the stratum corneum’s structural transition after applying DESs. The results showed that the l-menthol-based DESs with longer hydrocarbon chains disrupt lipid layers more than those with shorter hydrocarbon chains. Thymol-based DES extracted the lipids in the stratum corneum and permeated the corneocytes. Transepidermal water loss measurements showed that l-menthol-based DESs with longer hydrocarbon chains and thymol-based DESs damage skin as they disturb the inner parts of stratum corneum lipids. Overall, we concluded that DESs with longer hydrocarbon chains can be used as skin permeation enhancers for various drugs by reducing skin irritation.

Fluorescence of pyrene and its derivatives to reveal constituent and composition dependent solvation within hydrophobic deep eutectic solvents.

Depending on their constituents and composition, deep eutectic solvents (DESs) may exhibit widely varying physicochemical properties. Based on the miscibility of water in a DES, it can broadly be classified as 'hydrophobic' or 'hydrophilic'. The polarity offered by hydrophobic DESs as compared to common organic solvents in the context of solute solubilization thus becomes of the utmost importance. A versatile fluorescence probe, pyrene (Py), its aldehyde derivative, pyrene-1-carboxaldehyde (PyCHO), and a termini end-tagged dipyrenyl polydimethylsiloxane polymer (Py-PDMS-Py) are employed to assess the solvation environment afforded by DESs composed of thymol (Thy), (-)-menthol (Men), and n-decanoic acid (DA). To decipher the effect of the constituents and composition on solute solvation, DESs composed of different pairs of constituents in different molar ratios, namely Thy : Men (1 : 1 and 1 : 2), DA : Men (1 : 1 and 1 : 2), and Thy : DA (2 : 1, 1 : 1, and 1 : 2), are investigated. Pyrene, through its band 1-to-band 3 emission intensity ratio (Py I1/I3), displays higher cybotactic region dipolarity in Thy-containing DESs due to the phenyl ring of Thy; the sensitivity of Py I1/I3 towards temperature is also higher in Thy DESs. The fluorescence lifetime of pyrene and its temperature dependence are higher in Men-containing DESs in comparison. Quenching of pyrene fluorescence by nitromethane in these DESs is dynamic in nature and the recovered bimolecular quenching rate constants (kq) reveal efficient diffusion of the fluorophore-quencher pair in these DESs as compared to other iso-viscous media. The kq adheres to the Stokes-Einstein relation, implying inherent homogeneity associated to these DESs. PyCHO emission spectra show a high energy structured band in Thy : Men DESs, whereas the band shifts bathochromically and becomes broad in DA-containing DESs. The PyCHO cybotactic region is relatively nonpolar in Thy : Men DESs as compared to Thy : DA and Men : DA DESs. The extent of intramolecular excimer formation by Py-PDMS-Py reveals these DESs to be "good" solvents for polymer solvation where DES-polymer interactions are maximized. The microviscosity (ημ) surrounding Py-PDMS-Py correlates with the bulk dynamic viscosity (ηbulk) within the investigated DESs, further corroborating the absence of microheterogeneity. Overall, the observations reveal the similarity of these hydrophobic DESs to common organic solvents in the context of solute solubilization.

Nanobiocatalysts with inbuilt cofactor recycling for oxidoreductase catalysis in organic solvents.

The major stumbling block in the implementation of oxidoreductase enzymes in continuous processes is their stark dependence on costly cofactors that are insoluble in organic solvents. We describe a chemical strategy that allows producing nanobiocatalysts, based on an oxidoreductase enzyme, that performs biocatalytic reactions in hydrophobic organic solvents without external cofactors. The chemical design relies on the use of a silica-based carrier nanoparticle, of which the porosity can be exploited to create an aqueous reservoir containing the cofactor. The nanoparticle core, possessing radial-centred pore channels, serves as a cofactor reservoir. It is further covered with a layer of reduced porosity. This layer serves as a support for the immobilisation of the selected enzyme yet allowing the diffusion of the cofactor from the nanoparticle core. The immobilised enzyme is, in turn, shielded by an organosilica layer of controlled thickness fully covering the enzyme. Such produced nanobiocatalysts are shown to catalyse the reduction of a series of relevant ketones into the corresponding secondary alcohols, also in a continuous flow fashion.

Solidified floating organic drop microextraction procedure based on deep eutectic solvent for the determination of melatonin in pharmaceuticals and dietary supplements

A miniaturized clean-up and preconcentration procedure involving deep eutectic solvent-based solidified floating organic drop microextraction was developed for the determination of melatonin in pharmaceuticals and dietary supplements by high-performance liquid chromatography with UV detection. Melatonin is widely used for the treatment of a large spectrum of diseases, and many studies have focused on its efficacy in reducing COVID-19 severity. For the first time, various hydrophobic deep eutectic solvents based on menthol, medium-chain fatty acids, and long-chain alcohols were studied for the microextraction of melatonin. Among the studied solvents, the deep eutectic solvent based on menthol and heptanoic acid provided the highest extraction recovery (90 %). In the developed procedure, a flat magnetic stirrer bar was covered by a microliter amount of the deep eutectic solvent and the sample solution was added under magnetic stirring. In this case, the deep eutectic solvent phase was easily dispersed into the aqueous phase without the use of any organic disperser solvents, resulting in fast analyte extraction (1 min). In the absence of stirring, the aggregation of extract as a floating drop on the surface of the aqueous phase was observed immediately. The low melting/freezing point and low density of the extraction solvent compared with water allowed one to quickly and easily retrieve a low volume of extract (25 μL) in a microextraction procedure by solidification. Validation of the procedure showed that limits of detection and quantification, calculated from the blank tests based on 3σ and 10 σ, were 0.003 mg g−1 and 0.01 mg g−1, respectively.

Experimental investigation and thermodynamic modeling of cannabidiol solubility in plant oils and hydrophobic eutectic systems

Cannabidiol (CBD) is one of the most important cannabinoids found in hemp plants, having numerous applications in the pharmaceutical and food industries. Due to its low solubility in water, CBD is usually supplied in hydrophobic solvents. The present work investigated the solubility of CBD in ten plant oils and various systematically designed hydrophobic eutectic systems (ESs). The CBD solubility was found to correlate with the molecular weight and structure of the oils and ES constituents. CBD was more soluble in medium-chain triglyceride oils than in oils containing long-chain unsaturated fatty acids. Moreover, the CBD solubility was found to be higher in ESs than in oils. The conductor-like screening model for realistic solvents (COSMO-RS) was then applied to estimate the CBD solubility in oils and ESs. COSMO-RS did not provide satisfactory predictions of the CBD solubility in oils, possibly because oils were regarded as simple mixtures of fatty acids. On the other hand, COSMO-RS predicted well the CBD solubility in ESs. This work showed that newly-designed hydrophobic ESs could be alternative green solvents for CBD formulation and extraction.