Search Results (207)

The article presents the first method based on high-performance liquid chromatography and ultraviolet detection (HPLC-UV) for the determination of timonacic (thioproline, 1,3-thiazolidine-4-carboxylic acid, tPro) in pharmaceutical tablets and face care products (creams, sera, foundations, suncreams). Sample preparation primarily involves solid-liquid extraction (SLE) of tPro with 0.2 mol/L phosphate buffer pH 6, derivatization with 0.25 mol/L 2-chloro-1-methylquinolinium tetrafluoroborate (CMQT), followed by polytetrafluoroethylene (PTFE) membrane filtration. The chromatographic separation of the stable UV-absorbing 2-S-quinolinium derivative is achieved within 14 min at 25 °C on a Zorbax SB-C18 (150 × 4.6 mm, 5 µm) column using gradient elution. The eluent consists of 0.1 mol/L trichloroacetic acid (TCA), pH 1.7, in a mixture with acetonitrile (ACN) delivered at a flow rate of 1 mL/min. The analyte is quantified by monitoring at 348 nm. The assay linearity was observed within 0.5–125 μmol/L. The limit of quantification (LOQ) was found to be 0.5 μmol/L. The accuracy ranged from 93.22% to 104.31% and 97.38% to 103.48%, while precision varied from 0.30% to 11.23% and 1.13% to 9.64% for intra- and inter-assay measurements, respectively. The method was successfully applied to commercially available on the Polish market pharmaceutical and cosmetic products. Full article

This report presents the first method for simultaneous determination of the 2-S-lepidinium derivatives of total α-lipoic acid (LA), homocysteine (Hcy), cysteinylglycine (CysGly), and cysteine (Cys) in human saliva, using capillary electrophoresis with pH-mediated sample stacking and ultraviolet detection (CE-UV) at 355 nm. Electrophoretic separation is carried out at 20 kV and 25 °C using a standard fused silica capillary (effective length 91.5 cm, inner diameter 75 µm). The background electrolyte consists of 0.5 mol/L lithium acetate buffer, adjusted to pH 3.5 with 0.5 mol/L acetic acid. The limit of quantification was determined to be 1 µmol/L for LA and 0.17 µmol/L for Hcy, 0.11 µmol/L for CysGly, and 0.10 µmol/L for Cys in saliva samples. Calibration curves demonstrated linearity over the concentration range of 3 to 30 µmol/L for all analytes. Method precision did not exceed 4.7%, and accuracy ranged from 87.9% to 114.0%. The developed method was successfully applied to saliva samples from eleven apparently healthy volunteers to determine the content of LA, Hcy, CysGly, and Cys. The Hcy, CysGly, and Cys concentrations ranged from 0.55 to 13.76 µmol/L, 0.89 to 9.29 µmol/L, and 1.73 to 12.99 µmol/L, respectively. No LA-derived peaks were detected in the native saliva samples. Full article

New chiral salen-based organic salts were synthesised and evaluated for their antibacterial activity against Serratia fonticola, Escherichia coli, and Enterobacter cloacae. Their structures and physicochemical properties, namely their specific rotation, melting point, thermal stability, and antibacterial efficacy, including minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), were determined. The synergy between chiral organic salts and bacteriophages was also demonstrated. [(RR)Sal.5C1.PhIM][Cl], [(RR)Sal.5C1.PhIM][BF₄], and [(RR)Sal.5C1.Pyr][OTf] had the lowest MIC values (from 500 mg mL⁻¹ for S. fonticola strain KKP 3685 to 2000 mg mL⁻¹ for E. cloacae strain KKP 3692), while the highest MICs (>4000 mg mL⁻¹) were observed for [(RR)Sal.5C1.Pyr][OTf] and [(RR)Sal.5C1.PhIM][NTf₂] against E. cloacae strain KKP 3692. The impact of the tested compounds on phage activity was strain-specific. A synergistic effect of [(RR)Sal.5C1.PhIM][BF₄] at 0.5 mg mL⁻¹ in microcultures with Escherichia phage KKP 3710 (at MOI of 10 and 100) on the complete inhibition of the growth of E. coli strain KKP 3688 was observed. The combination of [(RR)Sal.5C1.PhIM])][OTf] at 1 mg mL⁻¹ with the addition of phages (at each MOI) and at 0.5 mg mL⁻¹ and MOI = 100 completely inhibited the growth of E. coli strain KKP 3688. Moreover, [(RR)Sal.5C1.PhIM])][OTf] at 1 mg mL⁻¹ and 0.5 mg mL⁻¹, when combined with Enterobacter phage KKP 3716, inhibited the growth of E. cloacae strain KKP 3692 slightly more effectively than the compound alone at the same concentrations. These results suggest that combining our antibacterial agents can reduce chemical compound concentrations, with effects depending on the bacteria. Full article

Ionic liquids (ILs) have been explored as a way of improving the performance of ZnO-based optoelectronic devices; however, there are few fundamental studies of the IL/ZnO interface. Here, the adsorption of the IL 1-octyl-3-methylimidazolium tetrafluoroborate [C₈C₁Im][BF₄] on ZnO (0001) and ZnO ($10\overline{1}0$) has been studied using synchrotron-based soft X-ray photoelectron spectroscopy. The results indicate that [C₈C₁Im][BF₄] is deposited intact on the ZnO (0001) surface; however, there is some dissociation of [BF₄]⁻ anions, resulting in boron atoms attaching to the oxygen atoms in the ZnO surface and forming B₂O₃. In contrast, the deposition of [C₈C₁Im][BF₄] on the ZnO ($10\overline{1}0$) surface at −150 °C results in the appearance of more chemical environments in the spectra. We propose that the high temperature of the IL evaporator causes some conversion of [C₈C₁Im][BF₄] to a carbene–borane adduct, resulting in the deposition of both the IL and adduct onto the ZnO surface. The adsorption and desorption of the analogous IL 1-butyl-3-methylimidazolium tetrafluoroborate [C₄C₁Im][BF₄] was investigated on ZnO (0001) using synchrotron-based soft X-ray photoelectron spectroscopy. The results indicate that [C₄C₁Im][BF₄] is deposited largely intact at −150 °C and forms islands when heated to room temperature. When heated to over 80 °C, it begins to react with the ZnO surface and decomposes. This is a much lower temperature than the long-term thermal stability of the pure IL, quoted in the literature as ~400 °C, and of IL on powdered ZnO, quoted in the literature as ~300 °C. This indicates that the ZnO surface may catalyse the thermal decomposition of [C₄C₁Im][BF₄] at lower temperatures. This is likely to have a negative impact on the potential use of ILs in ZnO-based photovoltaic applications, where operating temperatures can routinely reach 80 °C. Full article

The wide operating temperature and voltage window are favourable properties that increase the practical applications of supercapacitors. Ionic liquids (IL) are suitable electrolytes that allow supercapacitors to be used in wide operating ranges. In this study, triethylammonium tetrafluoroborate (Et₃NHBF₄) is tested as a new IL to operate supercapacitors in a wide temperature range (−40 °C, 25 °C, and 80 °C) in the presence of commercial activated carbon. The performance of Et₃NHBF₄ is compared to two different commercial ILs. This study also investigates the application of heat treatment to determine suitable activated carbon surface characteristics for ILs. The results indicate that heat treatment enhances the electrode–electrolyte interaction, and the electrochemical performances of the supercapacitors prepared from the heat-treated activated carbon are significantly higher than the original commercial activated carbon. Electrochemical tests show that the synthesised Et₃NHBF₄ (with propylene carbonate) can be used over a wide temperature range and has a better energy storage performance, especially at −40 °C (specific capacitance of 42.12 F/g at 2 A/g), compared to the other two commercial ionic liquids. Full article

Five new coordination compounds that included three coordination polymers and two supramolecular complexes were obtained by reactions of different cadmium salts (tetrafluoroborate, nitrate, and perchlorate) with dianiline chromophores, 4,4′-diaminodiphenylmethane (ddpm), and 4,4′-diaminodiphenylethane (ddpe). The crystal structures were studied by single-crystal X-ray analysis. The coordination arrays with the ddpm chromophore included {[Cd(OH)(H₂O)(ddpm)₂](BF₄)}_n (1) as a one-dimensional (1D) coordination garland chain, {[Cd(NO₃)(ddpm)₂](H₂O)(NO₃)}_n (2) as a two-dimensional (2D) coordination layer, and [Cd(bpy)₂(ddpm)₂](ddpm)(NO₃)₂ (3) as a supramolecular complex. The products with the ddpe chromophore were identified as {[Cd(phen)₂(ddpe)](ClO₄)₂}_n (4) in the form of a linear coordination chain and [Cd(phen)₃](ClO₄)₂(ddpe)_0.5(CH₃CN)_0.5 (5) as a supramolecular complex. The extension of coordination arrays in 1, 2, and 4 was achieved via dianiline ligands as bidentate linkers and additionally via bridging of nitrate anions in 2. The diversification of products became possible due to usage of 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) as co-ligands forming the terminal corner fragments [Cd(bpy)₂]²⁺, [Cd(phen)₂]²⁺, and [Cd(phen)₃]²⁺ in 3–5, respectively. The assembling of coordination entities occurred via the interplay of hydrogen bonds with the participation of amino groups, water molecules, and inorganic anions. Two dianilines were powerful luminophores in the crystalline phase, while the photoluminescence in 1–5 was considerably weaker than in the pure ddpm and ddpe luminophores and redistributed along the spectrum. Full article

A ferrocenium-catalyzed synthesis of trisubstituted tetrahydrofurans by dehydrative cyclization of diols is reported. Treatment of γ-phenyl-γ-butyrolactone or valerolactone with 2–3 equivalents of MeLi, n-BuLi, or PhLi yielded the corresponding substituted 1,4-butanediols in 41–86% yields. Subsequent dehydrative cyclization of the diols under non-inert conditions using catalytic ferrocenium tetrafluoroborate (10 mol%) produced trisubstituted tetrahydrofurans in 72–83% yields after 48–72 h at 45–70 °C in CH₂Cl₂. This study demonstrates ferrocenium-catalyzed dehydrative cyclization for the first time, offering a convenient route to substituted tetrahydrofurans in two steps from commercial or easily accessible starting materials. Full article

The electrochemical properties of the hydrophobic room-temperature ionic liquid 1-propyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide (PMMIm(TFSI)) were investigated, for the first time, using an electrochemical double-layer capacitor-mimicking cell containing two identical-sized micro–mesoporous molybdenum carbide-derived carbon electrodes (MMP-C(Mo₂C)), by applying cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Surprisingly, despite the substitution of the slightly acidic hydrogen atom with a methyl group at the carbon atom located between two nitrogen atoms in the imidazolium cation, the EIS and CV measurements demonstrated that PMMIm(TFSI) began to decompose electrochemically at the same cell potential (ΔE) as 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIm(BF₄)), specifically at ΔE = 2.75 V. However, the CV and EIS data indicated that PMMIm(TFSI) decomposed with a significantly lower intensity than EMIm(BF₄). Therefore, we believe that the use of PMMIm(TFSI) as the electrolyte will enable the construction of safer supercapacitors that can tolerate short periods of over-polarization up to ΔE = 4.0 V. However, when the ΔE ≤ 3.2 V was applied, EMIm(BF₄) offered higher maximum power compared to PMMIm(TFSI). We found that the calculated maximum gravimetric power precisely describes the maximum ΔE applicable for a supercapacitor candidate. Full article

Recent studies have shown that DHA supplementation in the form of phospholipids effectively increases DHA levels in the brain, including DHA lysophospholipids. This research explores a method to produce DHA lysophosphatidylcholine (DHA-LPC) using lipases and phospholipases immobilized on Immobeads-C18 with maximal enzyme loading. The esterification of glycerophosphatidylcholine (GPC) and DHA was studied with ionic liquids as alternatives to traditional solvents, with 1-methyl-3-octylimidazolium tetrafluoroborate (MOIM-BF₄) providing the highest yield due to its ability to increase the solubility of GPC. The reaction parameters were modified to establish a molar ratio of GPC to DHA of 1/10. A maximum DHA-LPC yield of 80% was achieved in 48 h, with a formation rate of 20.06 (mg/mL.h) × g. The Quara^® LowP biocatalyst (QlowP-C18) maintained 100% activity during the first three cycles and produced 788 mg of DHA lysophospholipid. The use of 50% MOIM-BF₄ improved the stability of the biocatalyst, and NMR confirmed that the product was the sn1-DHA-LPC isomer. Full article

Quercetin in Taraxacum mongolicum was extracted by ultrasound-assisted extraction in synergy with an ionic liquid–enzyme complex system, and the antioxidant function of quercetin was investigated based on network pharmacology. From 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium bromide, and 1-butyl-3-methylimidazolium tetrafluoroborate, the first step was to choose the appropriate ionic liquid. Subsequently, a response surface methodology and single-factor experiment were used to optimize the extraction process. The quercetin and the key targets for antioxidants were obtained from a public database. Antioxidant activity was assessed by measuring the scavenging rate of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and hydroxyl radicals(•OH). The approach revealed that the optimal extraction process was the liquid–solid ratio of 31.62:1 mL/g, enzymatic temperature of 55 °C, and the amount of cellulase added was 14.79% of the dry weight of dandelion. Under this condition, the yield of quercetin was 0.24 ± 0.011 mg/g, which was 1.3 times higher than that of the conventional reflux extraction method of 0.185 ± 0.015 mg/g. Pharmacological findings showed 57 cross-targets of quercetin with antioxidants. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis indicated that antioxidant function may be related to chemical carcinogenesis-reactive oxygen species, and the Phosphoinositide 3-kinase/protein kinase B signaling pathway. Quercetin has strong DPPH and •OH radical scavenging activity. The development and use of industrial dandelion are supported by this sustainable and effective method of extracting quercetin from dandelion. Full article

This article compares the rheological and tribological properties of three ionic liquids: Tributyl(methyl)phosphonium dimethyl phosphate 97%—MFCD, 1-Butyl-3-methylimidazolium hexafluorophosphate 97%—BMIMPF6, and 1-Butyl-3-methylimidazolium tetrafluoroborate 98%—BMIMBF4. Their density and kinematic viscosity at 20 °C and 40 °C were investigated, and tribological tests were carried out at the same temperatures with ball-on-disc contact. The test materials were made of 100Cr6 steel. A scanning electron microscope was used to image the wear tracks, while an EDS analyzer was employed to determine the chemical composition at the points of wear on the samples. A confocal microscope was used to analyze the geometric structure of the samples before and after the tribological tests. The results of the tests indicated that an increase in temperature reduced the dynamic viscosity of all the ionic liquids tested. At the same time, an increase in the MFCD and BMIMBF4 ionic liquid density and a decrease in the density of the BMIMPF6 ionic liquid were observed. The BMIMPF6 ionic liquid used for this study provided the lowest value of linear wear at both temperatures, ambient and 40 °C. However, for the BMIMBF4 ionic liquid, significant wear was observed for the tested discs and balls, with corrosive pitting on their surfaces. Full article

It is necessary to overcome the relatively low conductivity of ionic liquids (ILs) caused by steric hindrance effects to improve their ability to passivate defects and inhibit ion migration to boost the photovoltaic performance of perovskite solar cells (PSCs). Herein, we designed and prepared a kind of low-concentration 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄) diluted with propylene carbonate (PC) via an ultrasonic technique (PC/IL). The decrease in the decomposition temperature related to the IL part and the increase in the sublimation temperature related to the PC part facilitated the use of PC/IL to effectively delay the crystallization process and passivate the defects in multiple ways to obtain high-quality perovskite films. Moreover, the increased conductivity of PC/IL and the more matched band alignment accelerated electron transport and collection. Finally, the MAPbI₃- and CsMAFA-based PSCs achieved PCE values of 20.87% and 23.29%, respectively, and their stabilities were greatly improved. This work provides a promising approach to optimizing ILs to achieve multiple functions and boost the performance of PSCs. Full article

Nafion^® is a cation exchange polymer that is commonly used in aqueous energy applications such as fuel cells due to its ability to exclude anions and neutral molecules and increase apparent diffusion of cationic redox molecules. However, this behavior is not well studied in nonaqueous solutions. The behavior of platinum electrodes modified with recast Nafion^® films in nonaqueous solutions was observed to be different from its well-studied behavior in aqueous solutions. The reversible redox couple tris(2,2′-bipyridine)ruthenium(II) hexafluorophosphate was studied in the nonaqueous, aprotic solvent acetonitrile with different electrolytes (tetrabutylammonium tetrafluoroborate, tetrabutylammonium trifluoromethanesulfonate, tetrabutylammonium hexafluorophosphate, and ammonium trifluoromethanesulfonate) using cyclic voltammetry and rotating disk voltammetry. An unmodified platinum electrode in the nonaqueous systems and a recast Nafion^®-modified platinum electrode equilibrated in an aqueous solution of tris(bipyridine)ruthenium(II)chloride hexahydrate were used as controls. Results indicate that the polymer structure in acetonitrile conditions does not allow apparent (Dahms–Ruff) diffusion but does allow significant physical diffusion that would make Nafion a great immobilization option for modifying electrodes with catalysts in nonaqueous systems. Full article

Background: The increasing prevalence of antimicrobial resistant highlights the urgent need for the new therapeutic agents. This study aimed to design and synthesize fused tricyclic benzimidazole–thiazinone derivatives (CS1–CS10) through a convenient method and evaluate their antimicrobial activity against various microorganisms. Methods: A series of fused tricyclic benzimidazole–thiazinone derivatives was rationally designed and synthesized in one pot by the reaction between trans substituted acrylic acids and 1H-benzo[d]imidazole-2-thiol using coupling reagent TBTU (2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate). The structure of these compounds was confirmed through various spectroscopic techniques like IR, ¹H and ¹³C NMR, the DEPT and 2D-HMQC NMR techniques were also performed to confirm the relation of both carbon and proton. Further, the compounds were in vitro evaluated for their effectiveness against the Candida species and a panel of standard bacterial isolates. Results: The synthesized compounds showed moderate antimicrobial activity. Among all of the compounds, CS4 exhibited potent inhibition against Pseudomonas aeruginosa and Escherichia coli at 256 and 512 μg/mL concentrations, respectively. Additional research indicated that compound CS4 demonstrated a synergistic effect after combining with the standard antibacterial drug ciprofloxacin. Conclusions: These results suggest that CS4 is the best-synthesized antibacterial agent particularly in combination therapies. These findings highlight its promise for further development as a novel antibacterial agent. Full article

Background/Objectives: Typhoid and paratyphoid fever together are responsible for millions of cases and thousands of deaths per year, most of which occur in children in South and Southeast Asia. While typhoid conjugate vaccines (TCVs) are licensed, no vaccines are currently available against S. Paratyphi A. Here we describe the design of a S. Paratyphi A conjugate. Methods: The serovar-specific O-antigen (O:2) was linked to the CRM₁₉₇ carrier protein (O:2–CRM₁₉₇) and a panel of conjugates differing for structural characteristics were compared in mice and rabbits. Results: We identified the O-antigen molecular size, polysaccharide to protein ratio, conjugate cross-linking, and O:2 O-acetylation level as critical quality attributes and identified optimal design for a more immunogenic vaccine. Conclusions: This work guides the development of the O:2–CRM₁₉₇ conjugate to be combined with TCV in a bivalent formulation against enteric fever. Full article