Search Results (132)

This review surveys recent advances and emerging prospects in phase-transfer catalysis (PTC) for fuel desulfurization. In response to increasingly stringent environmental regulations, the removal of sulfur from transportation fuels has become imperative for curbing SO_x emissions. Conventional hydrodesulfurization (HDS) operates under severe temperature–pressure conditions and displays limited efficacy toward sterically hindered thiophenic compounds, motivating the exploration of non-hydrogen routes such as oxidative desulfurization (ODS). Within ODS, PTC offers distinctive benefits by shuttling reactants across immiscible phases, thereby enhancing reaction rates and selectivity. In particular, PTC enables efficient migration of organosulfur substrates from the hydrocarbon matrix into an aqueous phase where they are oxidized and subsequently extracted. The review first summarizes the deployment of classic PTC systems—quaternary ammonium salts, crown ethers, and related agents—in ODS operations and then delineates the underlying phase-transfer mechanisms, encompassing reaction-controlled, thermally triggered, photo-responsive, and pH-sensitive cycles. Attention is next directed to a new generation of catalysts, including quaternary-ammonium polyoxometalates, imidazolium-substituted polyoxometalates, and ionic-liquid-based hybrids. Their tailored architectures, catalytic performance, and mechanistic attributes are analyzed comprehensively. By incorporating multifunctional supports or rational structural modifications, these systems deliver superior desulfurization efficiency, product selectivity, and recyclability. Despite such progress, commercial deployment is hindered by the following outstanding issues: long-term catalyst durability, continuous-flow reactor design, and full life-cycle cost optimization. Future research should, therefore, focus on elucidating structure–performance relationships, translating batch protocols into robust continuous processes, and performing rigorous environmental and techno-economic assessments to accelerate the industrial adoption of PTC-enabled desulfurization. Full article

In the chemistry of bio-based furans, the Diels–Alder reaction plays an important role as a renewable route for the synthesis of fuels, fine chemicals, and monomers. Nonetheless, the unfavorable kinetic and thermodynamic parameters inherent to the Diels–Alder reaction involving furans as dienes often lead to the reversibility of cycloaddition, resulting in decreased equilibrium conversion and diastereoselectivity. In this study, we present a new strategy for overcoming the problem of reversibility in chemical reactions. We demonstrate that conducting the reaction under solvent-free conditions can facilitate the transition from a molten state formed by the initial reactants to a solid phase containing the reaction product along with an excess of the initial substrate. According to our results, such a liquid-to-solid transition of the reaction mixture can lead to exceptionally high conversion and diastereoselectivity in the furan–maleimide Diels–Alder reaction, particularly for challenging electron-poor furanic substrates. Our approach enables the reversible furan–maleimide Diels–Alder reaction to be performed in a cleaner and more environmentally friendly manner, free from the complexities associated with the use of solvents and the need for purification from side products. Full article

Propolis is a natural resinous substance produced by honeybees that has many biological activities. For thousands of years, it has been widely used as a dietary supplement and traditional medicine to treat a variety of ailments due to its antimicrobial, anti-inflammatory, antioxidant, immunomodulatory, and wound-healing properties. Nutritional supplements and foods may interact with drugs both pharmacodynamically and pharmacokinetically, which could raise clinical concerns. Background/Objectives: This study aimed to investigate the effect of propolis on the plasma disposition of enrofloxacin and to assess the potential pharmacokinetic interaction in rabbits. Methods: In this study, enrofloxacin was applied per os (20 mg/kg) and IM (10 mg/kg) and with propolis (100 mg resin/kg) administration in four groups of rabbits (each of six individuals). Heparinized blood samples were collected at 0, 0.1, 0.3, 0.5, 1, 2, 4, 8, 12, and 24 h post-administration. HPLC-FL was used to analyze the plasma concentrations of enrofloxacin and its active metabolite ciprofloxacin following liquid–liquid phase extraction, i.e., protein precipitation with acetonitrile and partitioning with sodium sulfate. Results: The results revealed that propolis coadministration significantly affected the plasma disposition of enrofloxacin and its active metabolite after both per os and intramuscular administration routes. Significantly greater AUC (48.91 ± 11.53 vs. 26.11 ± 12.44 µg.h/mL), as well as longer T_1/2λz (11.75 ± 3.20 vs. 5.93 ± 2.51 h) and MRT (17.26 ± 4.55 vs. 8.96 ± 3.82 h) values of enrofloxacin and its metabolite ciprofloxacin, were observed after the coadministration of propolis compared to enrofloxacin alone following both per os and IM routes in rabbits. Conclusions: The concurrent use of propolis and prescription medications may prolong the half-life (T_1/2λz) and increase the systemic availability of chronically used drugs with narrow therapeutic indices. The repeated use of drugs such as antibiotics, heart medications, and antidepressants, or drugs with a narrow therapeutic index such as antineoplastic and anticoagulant agents, can cause toxic effects by raising blood plasma levels. Considering the varied metabolism of rabbits and humans, further validation of this study may require thorough clinical trials in humans. Full article

Biomass liquefaction is a promising thermochemical route to convert lignocellulosic residues into bio-oil. This study evaluates the liquefaction behavior of 13 biomasses with varying particle sizes (0.3–2.0 mm) and moisture contents (5–11%) under mild solvolysis conditions. High-performance liquid chromatography (HPLC-RID) and thermogravimetric analysis (TGA) were used to characterize bio-oil composition and biomass properties, respectively. Maximum conversion (72%) was achieved for Miscanthus, while Ulva lactuca reached only 23% due to its low carbohydrate content. Hemicellulose-rich feedstocks showed higher yields, whereas high lignin content generally reduced conversion. Furfural was the main compound identified in the aqueous phase (up to 51 g/L), reflecting extensive pentose degradation. Laboratory and industrial-scale liquefaction of cork and eucalyptus revealed scale-dependent differences. Industrial cork bio-oil showed increased xylose (0.70 g/L) and furfural (0.40 g/L), while industrial eucalyptus exhibited elevated levels of acetic (0.46 g/L) and formic acids (0.71 g/L), indicating enhanced deacetylation and demethoxylation reactions. These findings offer valuable insights for optimizing feedstock selection and process conditions in biomass liquefaction. The valorization of lignocellulosic residues into bio-oil contributes to the development of scalable, low-carbon technologies aligned with circular economy principles and bio-based industrial strategies. Full article

SiC-W₂B₅/C composites were prepared through a novel and simple processing route (reaction hot-pressing). The density of composites increased from 96.1% to 99.2% with the increase in SiC content from 5 to 30 vol%, leading to significant improvements in mechanical properties such as flexural strength, fracture toughness, and Vickers hardness, which for the highest W15S30 composite were measured at 292.3 MPa, 6.12 MPa·m^1/2, and 3.32 GPa, respectively. The fracture morphology exhibited a mixed fracture mode of transgranular and intergranular, along with a pull-out phenomenon, indicating a well-combined interface. The sintering process involved Si powder acting as a liquid-phase sintering agent, reacting with B₄C to increase the B concentration and promote the generation of W₂B₅, as well as reacting with the carbon phase to generate a transition phase of Si-B-C. The presence of this transition phase enhanced the interface bonding strength and catalyzed the graphitization process. As the SiC content increased, the promotion effect became more pronounced, with the degree of graphitization increasing from 59.2% to 66.2%. Full article

The efficient liquefaction of cellulose is a critical technological pathway for the energy utilization of biomass. This study constructed a plasma electrolytic liquefaction experimental system based on the principle of liquid phase surface arc discharge, systematically investigating the effects of operational parameters, including working voltage, catalyst dosage, solid–liquid ratio, and micro-arc polarity, on the liquefaction characteristics of microcrystalline cellulose. Experimental results demonstrated that under optimized conditions—anode micro-arc configuration, working voltage of 750 V, catalyst dosage of 1.44 g, and solid–liquid ratio of 6:38—the cellulose conversion rate reached 79.2%, with a liquefied product mass of 4.75 g. Mechanistic analysis revealed that high-energy electrons and hydrogen ions generated by plasma discharge synergistically act on the cleavage of cellulose molecular chains. Under the combined effects of the catalyst and plasma, cellulose molecules are depolymerized into small molecular compounds. Compared with traditional liquefaction processes, this technology exhibits significant advantages in reaction rate and energy efficiency, providing a novel technical route for the efficient conversion of biomass resources. Full article

The metabolic cycle of L-proline plays a crucial role in cancer cell survival, proliferation, and metastasis. A key intermediate in the biosynthesis and degradation of proline is 3,4-dihydro-2H-pyrrole-2-carboxylic acid. A direct route for synthesizing substituted derivatives of this acid involves the cyclization of 2-amino-5-oxonitriles. Michael additions of [(diphenylmethylene)amino]acetonitrile to enones in a basic medium—either with aqueous sodium hydroxide or under solid–liquid phase-transfer catalysis conditions using CaO as a base—enable the synthesis of substituted 2-amino-5-oxonitriles as single diastereoisomers or as diastereoisomeric mixtures. Selective removal of the diphenylmethylene-protecting group, followed by in situ cyclization in acidic conditions, yields trans- and cis-3,5-diaryl-3,4-dihydro-2H-pyrrole-2-carbonitriles. The reaction of nitriles with HCl/dioxane/methanol followed by treatment with water produces esters and amides as by-products. In vitro screening of the synthesized compounds against multiple human cancer cell lines revealed that some compounds exhibit a good or high selectivity index. In conclusion, the synthetic schemes presented offer simple and efficient routes for the preparation of the derivatives of substituted 3,4-dihydro-2H-pyrrole-2-carboxylic acids, with some compounds exhibiting promising antiproliferative activity. Full article

Bioactive peptides are promising therapeutic agents due to their antimicrobial and anticancer activities, although their lack of selectivity often limits clinical applications. This study demonstrates the optimal synthetic route for conjugating folic acid (FA) with the bioactive peptide Lunatin-1, aiming to improve selectivity for neoplastic cells. The synthesis combines solid-phase peptide synthesis (SPPS) and Cu(I)-catalyzed cycloaddition to link folic acid to Lunatin-1 via a triazole ring. Using the model tripeptide FIG-_NH2, key intermediates and the final product were characterized by high-performance liquid chromatography (HPLC), mass spectrometry (MALDI-ToF), Fourier-transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR). Reaction yields and purity were optimized with FIG-_NH2, providing a reproducible synthesis pathway. Additionally, the results confirmed successful conjugation, with the FA-Trz-Luna product exhibiting molecular integrity and structural stability, as validated by spectral analyses. This study highlights a potential synthesis route for peptide-folate conjugates to be used as selective and multifunctional therapeutic agents, laying the groundwork for biological evaluations of their cytotoxicity and antimicrobial properties. Full article

Incidents involving hazardous materials (HAZMAT incidents) can impact human health and the environment. For the development of risk mitigation strategies, it is essential to understand the circumstances of such incidents. A retrospective study (2016–2023) of acute occupational HAZMAT incidents involving multiple patients (>1, including workers, emergency responders and bystanders) reported to the Dutch Poisons Information Center was conducted. We only included incidents that occurred during the performance of work or as a result of a disruption of a work-related process. Patient characteristics, exposure circumstances (such as the substances involved, chemical phase, and type of release (e.g., spill/release or fire/explosion)) and business classes were analyzed to identify risk factors. From 2016 to 2023, the DPIC was consulted about 516 HAZMAT incidents. Inhalation was the most common route of exposure (89%). Patients were often exposed to chemical asphyxiants (n = 156) and acids (n = 151). Most incidents occurred in fixed facilities (n = 447), while 49 incidents occurred during transport. The primary cause was a spill/release (n = 414), followed by a fire/explosion (n = 65). Most patients were exposed to a gas/vapor (n = 421), followed by a liquid (n = 59) or solid (n = 28). Incidents frequently occurred in industry (20%). The majority of patients reported mild to moderate health effects. Surveillance data on HAZMAT incidents are essential for incident preparedness. Poison Center data can help identify risk factors, which can be used to develop risk mitigation strategies to prevent future incidents. Full article

A novel class of SiO₂ aerogel-based resin composite with a self-formed foamy structure and an extremely low thermal conductivity, as well as excellent fire resistance, was fabricated via a room temperature and atmospheric pressure route. The self-formed foamy structure was achieved by utilizing SiO₂ aerogel particles not only as a thermal insulative functional additive filler but also as nano-sized solid particles in a Picking emulsion system, adjusting the surface tension as a stabilizer at the interface between the two immiscible phases (liquid and air in this case). The results of foamy structure analyses via scanning electron microscopy, micro-CT, and N₂ adsorption–desorption isotherms validate the successful generation of a micro-scale porous structure with the enhancement of the aerogel nano-scale solid particles at the wall as a stabilizer. A combination of multiscale pores imbues the aerogel-based foamy coating with a low thermal conductivity, as well as a high cohesive strength. For the foamy coating studied, with variable emulsion/foaming agent/aerogel ratios of 1/2/x, the thermal conductivity decreases from 0.141 to 0.031 W/m·K, and the cohesive strength increases from being non-detectable to 0.41 MPa. The temperature difference, which is a direct indicator of the thermal insulation behavior of the foamy coating, can increase from 12.1 °C to 48.6 °C under an 80 °C hot plate. Full article

Withania somnifera (common name: ashwagandha; WS) is an Ayurvedic botanical that has become popular for its reputed effects on stress and insomnia. Research into the bioactive compounds responsible for the biological effects of WS has largely focused on withanolides, a group of steroidal lactones commonly found in the Solanaceae family. Until recently, however, it was unclear which, if any, withanolides were present in the plasma after the ingestion of WS products. The aim of this review is to summarize current knowledge regarding the plasma pharmacokinetics of withanolides found in WS and the analytical methods developed to detect them in plasma. Twenty studies (sixteen animal, four human) were identified in which isolated withanolides or withanolide-containing products were administered to animals or humans and quantified in plasma. Withanolides were commonly analyzed using reversed-phase liquid chromatography coupled to mass spectrometry. Plasma concentrations of withanolides varied significantly depending on the substance administered, withanolide dose, and route of administration. Plasma pharmacokinetics of withaferin A, withanolide A, withanolide B, withanoside IV, 12-deoxywithastramonolide, and withanone have been reported in rodents (C_max range: 5.6–8410 ng/mL), while withaferin A, withanolide A, 12-deoxywithastramonolide, and withanoside IV pharmacokinetic parameters have been described in humans (C_max range: 0.1–49.5 ng/mL). Full article

The growing demand for more sustainable routes and processes in the mixture separation and purification industry has generated a need to search for innovations, with new solvent alternatives being a possible solution. In this context, a new class of green solvents, known as deep eutectic solvents (DESs), has been gaining prominence in recent years in both academic and industrial spheres. These solvents, when compared to ionic liquids (ILs), are more environmentally friendly, less toxic, low-cost, and easier to synthesize. In addition, they have significantly lower melting points than their precursors, offering a promising option for various applications in this industrial sector. Understanding and studying the thermodynamic behavior of systems composed of these substances in purification and separation processes, such as liquid–liquid extraction and azeotropic distillation, is extremely important. This work aimed to study the phase behavior of liquid–liquid equilibrium (LLE) and vapor–liquid equilibrium (VLE) of water + 1-butanol + DES (choline chloride + glycerol) systems with a molar ratio of 1:2. Experimental LLE data, obtained at 298.15 K and 101.3 kPa, and VLE data, obtained at 101.3 kPa and in the temperature range of 364.05 K–373.85 K, were submitted to the thermodynamic quality/consistency test, proposed by Marcilla et al. and Wisniak, and subsequently modeled using the gamma–gamma approach for the LLE and gamma–phi for the VLE. The non-random two-liquid (NRTL) model was used to calculate the activity coefficient. The results are presented for the VLE in a temperature–composition phase diagram (triangular prism) and triangular phase diagrams showing the binodal curve and tie lines (LLE). The separation and distribution coefficients of LLE were determined to evaluate the extractive potential of the DES. For the VLE, the values of the relative volatility of the system were calculated, considering the entrainer free-basis, to evaluate the presence or absence of azeotropes in the range of collected points. From these data, it was possible to compare DES with ILs as extracting agents, using data from previous studies carried out by the research group. Therefore, the results indicate that the NRTL model is efficient at correlating the fluid behavior of both equilibria. Thus, this study serves as a basis for future studies related to the understanding and design of separation processes. Full article

In this very personal hunt for the meaning of the bacterial cell cycle, the snark, I briefly revisit and update some of the mechanisms we and many others have proposed to regulate the bacterial cell cycle. These mechanisms, which include the dynamics of calcium, membranes, hyperstructures, and networks, are based on physical and physico-chemical concepts such as ion condensation, phase transition, crowding, liquid crystal immiscibility, collective vibrational modes, reptation, and water availability. I draw on ideas from subjects such as the ‘prebiotic ecology’ and phenotypic diversity to help with the hunt. Given the fundamental nature of the snark, I would expect that its capture would make sense of other parts of biology. The route, therefore, followed by the hunt has involved trying to answer questions like “why do cells replicate their DNA?”, “why is DNA replication semi-conservative?”, “why is DNA a double helix?”, “why do cells divide?”, “is cell division a spandrel?”, and “how are catabolism and anabolism balanced?”. Here, I propose some relatively unexplored, experimental approaches to testing snark-related hypotheses and, finally, I propose some possibly original ideas about DNA packing, about phase separations, and about computing with populations of virtual bacteria. Full article

Menbutone is a choleretic agent currently used in Europe to treat digestive disorders in livestock and dogs. Pharmacokinetic parameters were established in 4-month Holstein calves after intravenous (IV) and intramuscular (IM) administration. The drug was administered to 12 animals (10 mg/kg) for both IV and IM routes following a crossover design. Plasma samples were collected at various time points over 24 h and analyzed by reverse-phase high-performance liquid chromatography with a photodiode-array detector, following a method validated according to European Medicines Agency guidelines. Pharmacokinetic parameters were calculated using compartmental and non-compartmental methods. Menbutone followed a two-compartment open model after IV injection, with a total clearance (Cl) of 71.9 ± 13.5 mL/h/kg, an elimination half-life (t_½β) of 4.53 ± 2.45 h, and a volume of distribution at steady-state (V_ss) of 310.4 ± 106.4 mL/kg. Non-compartmental elimination half-life (t_½λ) was 4.2 ± 1.1 h. After IM administration, drug pharmacokinetics was best described by a one-compartment open model. The peak plasma concentration (C_max) was 15.1 ± 4.3 µg/mL; the time to reach C_max (t_max), 1.66 ± 0.55 h; and the mean absorption time (MAT), 2.50 ± 1.42 h. Absorption was high, with a fraction of the dose absorbed (F) of 83.5 ± 22.4%. Menbutone was rapidly eliminated from plasma for both routes of administration, with a fast and high IM bioavailability. Full article

Simulated body fluid (SBF) and artificial saliva (AS) are used in biomedical and dental research to mimic the physiological conditions of the human body. In this study, the biomimetic precipitation of double-doped amorphous calcium phosphate in SBF and AS are compared by thermodynamic modelling of chemical equilibrium in the SBF/AS-CaCl₂-MgCl₂-ZnCl₂-K₂HPO₄-H₂O and SBF/AS-CaCl₂-MgCl₂-ZnCl₂-K₂HPO₄-Glycine/Valine-H₂O systems. The saturation indices (SIs) of possible precipitate solid phases at pH 6.5, close to pH of AS, pH 7.5, close to pH of SBF, and pH 8.5, chosen by us based on our previous experimental data, were calculated. The results show possible precipitation of the same salts with almost equal SIs in the two biomimetic environments at the studied pHs. A decrease in the saturation indices of magnesium and zinc phosphates in the presence of glycine is a prerequisite for reducing their concentrations in the precipitates. Experimental studies confirmed the thermodynamic predictions. Only X-ray amorphous calcium phosphate with incorporated Mg (5.86–8.85 mol%) and Zn (0.71–2.84 mol%) was obtained in the experimental studies, irrespective of biomimetic media and synthesis route. Solid-state nuclear magnetic resonance (NMR) analysis showed that the synthesis route affects the degree of structural disorder of the precipitates. The lowest concentration of dopant ions was obtained in the presence of glycine. Further, the behaviour of the selected amorphous phase in artificial saliva was studied. The dynamic of Ca²⁺, Mg²⁺, and Zn²⁺ ions between the solid and liquid phases was monitored. Both direct excitation ³¹P NMR spectra and ¹H-³¹P CP-MAS spectra proved the increase in the nanocrystalline hydroxyapatite phase upon increasing the incubation time in AS, which is more pronounced in samples with lower additives. The effect of the initial concentration of doped ions on the solid phase transformation was assessed by solid-state NMR. Full article