Unstable Compounds Research Articles

Features of gas chromatographic analysis of thermally unstable compounds

Confirming the stability of analytes during gas chromatographic (GC) analysis is an important criterion, especially for previously uncharacterized compounds. However, the variations of absolute peak areas at different injector temperatures usually do not allow us to reveal the thermal instability of analytes during GC analysis. Such variations may be caused by peak area known discrimination typical for using capillary columns, especially at low split injection. The thermal instability can be revealed only when using relative peak areas.The dependences of the relative peak areas of unstable analytes on the injector temperature (descending), as well as similar dependences for products of their decomposition (ascending), are characterized by the existence of two limits. Low-temperature limits correspond to the initial quantities of unstable analytes, and high-temperature limits, to their complete transformations. Such dependences can be approximated with an equation of logistic regression (synonymous: sigmoid or Boltzmann approximation).The relationships and features of gas chromatographic analysis of thermally unstable compounds are considered with products of free-radical isopropylbenzene (cumene) chlorination and with solutions of ethyl diazoacetate in different solvents as examples. The major cumene chlorination product, (1-chloro-1-methylethyl)benzene, undergoes dehydrochlorination at injector temperatures above 200 °С to form a single product, α-methylstyrene. The analysis of the ethyl diazoacetate solutions is accompanied by the formation of ethyl alkoxyacetates, products of the insertion of intermediate ethoxycarbonylcarbene into OH bonds of alcohols, if they are used as solvents. Comparing the temperatures of half-conversion of the initial ester, T(50 %), and half-formation of the products shows that they are equal to each other. This confirms both the process mechanism and the correctness of the data approximation.

A high-throughput framework for lattice dynamics

We develop an automated high-throughput workflow for calculating lattice dynamical properties from first principles including those dictated by anharmonicity. The pipeline automatically computes interatomic force constants (IFCs) up to 4th order from perturbed training supercells, and uses the IFCs to calculate lattice thermal conductivity, coefficient of thermal expansion, and vibrational free energy and entropy. It performs phonon renormalization for dynamically unstable compounds to obtain real effective phonon spectra at finite temperatures and calculates the associated free energy corrections. The methods and parameters are chosen to balance computational efficiency and result accuracy, assessed through convergence testing and comparisons with experimental measurements. Deployment of this workflow at a large scale would facilitate materials discovery efforts toward functionalities including thermoelectrics, contact materials, ferroelectrics, aerospace components, as well as general phase diagram construction.

Enhancing safety in the storage of hazardous molecules: The case of hydroxylamine

Handling large quantities of thermally unstable compounds in storage vessels can result in severe accidents due to runaway reactions. Therefore, developing inherently safe design strategies for storage equipment is crucial for enhancing chemical plant reliability and preventing hazardous scenarios. The Frank-Kamenetskii theory (FKT) of self-heating offers practical tools for designing procedures to address phenomena that could lead to uncontrolled chemical reactions. This study introduces a design procedure based on the FKT for creating intrinsically safe storage vessels. An expanded FKT version incorporating parametric sensitivity analysis has been developed to improve the method's reliability. To understand self-heating phenomena, stability and performance diagrams were created, relating critical design parameters (e.g., the critical value of the Frank-Kamenetskii number) and verification parameters (e.g., maximum reached dimensionless temperature) to the dimensionless activation energy (γ). Additionally, the proposed design strategy includes a procedure for designing relief systems to mitigate the risk of equipment explosions from runaway reactions. The applicability of this procedure was tested using two cases: (I) an aqueous solution containing 50% w/w hydroxylamine (HA) and (II) a 50% w/w HA aqueous solution with 1% w/w hydroxylamine hydrochloride (HA-derived salt). Results indicate that for large γ values, the traditional FKT formulation and the expanded theory yield similar vessel designs. However, for finite γ values (γ≤100), the refined FKT version allows for less conservative storage equipment design. Combining DIERS guidelines with standard procedures for relief systems results in a more versatile and consistent protocol. However, incorporating relief systems is often impractical for large storage vessels due to the excessively large venting areas required for runaway reactions. In such cases, intrinsically safe vessel designs become the only feasible solution to prevent catastrophic incidents.

TLC with densitometric and image analysis in the control of anthocyanin content in fruits of Rubus occidentalis and Rubus idaeus cultivars and hybrids

A TLC method was developed for the determination of anthocyanins in the fruits of some cultivated varieties of Rubus occidentalis (black raspberries) and Rubus idaeus (red raspberries) and their hybrids. Anthocyanin sets in fruits’ extracts were determined on TLC silica gel 60 F254 plates using mobile phase consisted of ethyl acetate-water-formic-acid (100:30:30, V/V), at 4°C (±1°C), at a distance of 70 mm with the use of densitometry and videoscanning. The obtained results were comparable to the results of quantitative analysis performed using by the HPLC-UV/VIS method performed on a Kinetex C-18 column using gradient elution comprising an increase concentration of acetonitrile-water-trifluoroacetic acid (50:50:0.1, V/V) in water-trifluoroacetic acid (99.9:0.1, V/V) from 12 % to 40 % within 40 minutes at 520 nm. The TLC method with videoscanning provides immediate capture of data for unstable compounds like anthocyanins before their partial degradation.

Molecular understanding of speciation transformation of phosphorus and sulfur in food waste digestate during hydrothermal treatment

Recovering phosphorus (P) and sulfur (S) from biowaste is a key strategy to address the current P resources shortage and soil S deficiency. Food waste digestate (FWD) contains high contents of P and S, while its direct application is severely limited by available nutrient leaching loss and pollutant exposure. Hydrothermal treatment (HT) is an effective technique for biowaste disposal, enabling detoxification and resource recovery. The study systematically investigated the speciation transformation of P and S in FWD during HT, using chemical extraction and in-situ X-ray absorption near-edge structure (XANES) spectroscopy. The results revealed that up to 98% of P in FWD was enriched in the solid product (hydrochar) after HT, with organic P and labile P being converted into stable Ca-bound forms, predominantly hydroxyapatite. This transformation reduced the risk of P leakage loss compared to untreated FWD. Interestingly, the S speciation evolution exhibited more complexity. The highest S proportion in hydrochar of 73.6% was observed at 140 °C under HT. As the temperature increased from 140 °C to 180 °C, S in the hydrochar gradually dissolved into the liquid phase, attributed to unstable aliphatic compounds (mercaptan) and the sulfides oxidizing to sulfates. Above 180 °C, intermediate oxidation states and sulfates were reduced and formed metal sulfides. These findings have important implications for understanding the viability of HT for FWD disposal and the value-added utilization of FWD.

Two-step emulsification for the fabrication of homogeneous PCL microspheres encapsulating geniposidic acid with antioxidant properties

The mortality rate of neurological disorders is increasing globally, and natural antioxidant geniposidic acid (GPA) holds great potential in the treatment of neuronal oxidative damage. Nevertheless, its inherent instability constrains its pragmatic utilization. Herein, we introduced a drug delivery system capable of protecting unstable natural active compounds from degradation. Among the various methods for preparing drug-loaded microspheres, the emulsification-solvent evaporation technique is one of the most commonly employed due to its efficiency and simplicity. Nevertheless, this method results in microspheres with heterogeneous particle sizes. To address this limitation, we developed a two-step emulsification method involving stirring and homogenization. Using the biocompatible, synthetic, biodegradable polymer polycaprolactone (PCL) as the drug delivery carrier, we prepared GPA-loaded PCL microspheres via the two-step emulsification method. The results demonstrated that the microspheres possessed uniform particle size (polydispersity index = 0.12), excellent drug loading capacity (∼4.86%), sustained drug release profiles (∼68.55% in 264 h), and biocompatibility (cell viability >85%). The in vitro tests showed that the microspheres exerted antioxidant effects by scavenging reactive oxygen species (ROS) induced by oxidative stress, thereby protecting neuronal cells from oxidative damage. This work presents a promising new approach for the treatment of neuronal oxidative damage.

Advances in Nanoemulsion Formulations for Enhanced Drug Delivery: A Comprehensive Review

Abstract: Nanoemulsions (NEs) have emerged as adaptable medication delivery methods with extensive applications in both pharmaceuticals and cosmeceuticals. This comprehensive review delves into the myriad advantages of NEs, ranging from enhanced drug absorption to providing stability for chemically unstable compounds. NEs exhibit promising potential as substitutes for liposomes, offering improved performance in various formulations. In the realm of cosmeceuticals, NEs play a pivotal role in enabling rapid skin penetration while maintaining skin moisturization, thanks to their visually appealing coating. Their ability to deliver active ingredients efficiently makes them an attractive option for cosmetic formulations seeking enhanced efficacy. Moreover, this review sheds light on the involvement of NEs in antimicrobial therapies and gene therapy, underscoring their versatility and potential in addressing diverse medical challenges. Additionally, NEs find applications in commercial disinfectants, further highlighting their broad utility beyond traditional drug delivery systems. Furthermore, the review discusses innovative strategies, such as solid self-nanoemulsifying drug delivery systems (S-SNEDDS), which offer advantages in terms of stability, drug loading capacity, and patient compliance. By exploring these strategies, researchers aim to overcome existing limitations and optimize the therapeutic potential of NEs.

Full Selectivity Control over the Catalytic Hydrogenation of Nitroaromatics Into Six Products

AbstractA full selectivity control over the catalytic hydrogenation of nitroaromatics leads to the production of six possible products, i.e., nitroso, hydroxylamine, azoxy, azo, hydrazo or aniline compounds, which has however not been achieved in the field of heterogeneous catalysis. Currently, there is no sufficient evidence to support that the catalytic hydrogenation of nitroaromatics with the use of heterogeneous metal catalysts would follow the Haber's mechanistic scheme based on electrochemical reduction. We now demonstrate in this work that it is possible to fully control the catalytic hydrogenation of nitroaromatics into their all six products using a single catalytic system under various conditions. Employing SnO2‐supported Pt nanoparticles facilitated by the surface coordination of ethylenediamine and vanadium species enabled this unprecedented selectivity control. Through systematic investigation into the controlled production of all products and their chemical reactivities, we have constructed a detailed reaction network for the catalytic hydrogenation of nitroaromatics. Crucially, using oxygen‐isolated characterization techniques is essential for identifying unstable compounds such as nitroso, hydroxylamine, hydrazo compounds. The insights gained from this research offer invaluable guidance for selectively transforming nitroaromatics into a wide array of functional N‐containing compounds, both advancing fundamental understanding and fostering practical applications in various fields.

Full Selectivity Control over the Catalytic Hydrogenation of Nitroaromatics Into Six Products.

A full selectivity control over the catalytic hydrogenation of nitroaromatics leads to the production of six possible products, i.e., nitroso, hydroxylamine, azoxy, azo, hydrazo or aniline compounds, which has however not been achieved in the field of heterogeneous catalysis. Currently, there is no sufficient evidence to support that the catalytic hydrogenation of nitroaromatics with the use of heterogeneous metal catalysts would follow the Haber's mechanistic scheme based on electrochemical reduction. We now demonstrate in this work that it is possible to fully control the catalytic hydrogenation of nitroaromatics into their all six products using a single catalytic system under various conditions. Employing SnO2-supported Pt nanoparticles facilitated by the surface coordination of ethylenediamine and vanadium species enabled this unprecedented selectivity control. Through systematic investigation into the controlled production of all products and their chemical reactivities, we have constructed a detailed reaction network for the catalytic hydrogenation of nitroaromatics. Crucially, using oxygen-isolated characterization techniques is essential for identifying unstable compounds such as nitroso, hydroxylamine, hydrazo compounds. The insights gained from this research offer invaluable guidance for selectively transforming nitroaromatics into a wide array of functional N-containing compounds, both advancing fundamental understanding and fostering practical applications in various fields.

Pickering emulsions in food and nutraceutical technology: from delivering hydrophobic compounds to cutting-edge food applications

Pickering emulsions have emerged as suitable alternatives to healthily and sustainably deliver unstable compounds, addressing the demands of consumers, increasingly concerned about the nutritional value and environmental impact of the products they consume. They are stabilized by insoluble solid particles that partially hydrate both the oil (O) and aqueous (W) phases through a combination of steric and electrostatic repulsions determined by their surface properties. Since the desorption energy of the particles is very high, their adsorption is considered irreversible, which accounts for their greater stability compared to conventional emulsions. Proteins and polysaccharides, used either individually or in combination, can stabilize Pickering emulsions, and recent studies have revealed that microorganisms are also suitable stabilizing particles. This review provides an overview of recent research on Pickering emulsions, highlighting the properties of the stabilizing particles, and their ability to deliver hydrophobic and/or unstable compounds. The use of Pickering emulsions as fat-replacers, edible inks for 3D-printing or their incorporation into packaging material are also presented and discussed, pointing out their great potential for further innovation.

Colorimetry method for nitrocellulose powder charge monitoring system

Nitrocellulose powders are unstable chemical compounds. Over time, the consumer properties of the powder charge can change so much that the charges will not only be unsuitable for their intended use, but also become dangerous for personnel and the barrel system. This is associated with the problem of establishing the terms of safe storage of powders and their operational suitability, the need for a constant system for monitoring their condition. However, in developed NATO countries, there is practically no system for monitoring powder charges throughout their entire shelf life. Some countries have some components of the above-mentioned system, but its elements do not fully cover the entire spectrum of the state of powder charges. For the monitoring system to work effectively, informative indicators are needed that allow determining the state of powder charges without the use of complex diagnostic equipment. One of such indicators is the color of the surface of the powder element. In this study, an automated method for assessing the quality of nitrocellulose powder charges by the color of their surface for further use as intended was developed. The use of this method will significantly reduce the time of assessment and decision-making by experts, and eliminate subjectivity. In addition, the method will allow creating a database of powder charges for further monitoring of their condition throughout the entire life cycle. To confirm the reliability and adequacy of the developed method, an experimental study was conducted. The study data showed that the proposed hypothesis is true, namely, during storage, nitrocellulose powder charges change the color of their surface, and it is possible to determine their shelf life

Stereoselective Synthesis of Silyl Enol Ethers with Acylsilanes and α,β-Unsaturated Ketones.

Acylsilanes are emerging bench-stable reagents for the generation of electron-rich oxycarbenes that are difficult to access with unstable diazo compounds. Herein, we report a siloxycarbene-mediated stereoselective synthesis of silyl enol ethers through visible-light-induced intermolecular reactions between acylsilanes and α,β-unsaturated ketones. Both the solvent and low temperature are important for the success of the reaction. This approach features atomic economics, exclusive stereocontrol, and broad substrate scope. The synthetic potential of this methodology is demonstrated by gram-scale reaction and various downstream transformations including that requiring configuration purity of the silyl enol ethers.

Generation of pyridinylethylidenemalononitrile cyclic dimer: A facile route to multi-stimuli-responsive far-red/NIR luminogens

A simple synthetic strategy was successfully employed to develop NIR luminophores with switchable color-contrasting luminescence properties. D-A molecular motifs with dicyanovinylene appended pyridinyl moiety as the electron-withdrawing unit was not reported among luminescent molecules so far, owing to its unstable precursor compound pyridinylethylidenemalononitrile. By modifying the Knoevenagel condensation reaction pathways, the present work succeeded for the first time in identifying and crystallizing a novel cyclic dimerization product of the precursor compound. It further reports a new, simple, efficient synthetic route to achieve push-pull far-red/NIR emissive luminophores with the dicyanovinylene appended pyridinyl skeleton as the potent electron withdrawing unit. The enhanced charge transfer and the acidochromic characteristics make them suitable candidates in multi-stimuli-responsive smart materials with anti-counterfeiting applications.

New Encapsulation of Fucoxanthin Isolated from Cyclotella striata by Nano Chitosan–Pectin using Ionic Gelation Method

Fucoxanthin is an anticancer, antioxidant, antimicrobial, and anti-inflammatory bioactive compound. Unfortunately, the conjugated double bonds of the fucoxanthin structure make it unstable, posing issues for product development, particularly with regard to shelf life. This research study aims to synthesize nano chitosan–pectin and encapsulate isolated fucoxanthin by nano chitosan–pectin using an ionic gelation method. Fucoxanthin was obtained through isolation of microalgae species Cyclotella striata. The best result of nanoparticle size using a particle size analyzer was chitosan:pectin 1 : 2 of 172 nm. Fourier transform infrared analysis showed that there was an interaction between chitosan–pectin and fucoxanthin, which was characterized by a shift in the C O absorption fucoxanthin from 1736 to 1632 cm-1. The result of morphological analysis of nano chitosan–pectin–fucoxanthin using a scanning electron microscopeshows a spherical morphology with a size between 140 and 265 nm. The result of encapsulation efficiency was 75.18%, whereas encapsulation stability increased fucoxanthin oxidation half-life 4.7 times longer than that of unencapsulated fucoxanthin. The nano chitosan pectin could be utilized as a matrix conjugate to increase the stability of fucoxanthin significantly by encapsulation. This information is expected to be useful in developing encapsulation applications for unstable compounds.

Impact of pre- and post-fermentation fining with polyvinylpolypyrrolidone on the chemical stability and aromatic profile of Viognier wine.

Polyvinylpolypyrrolidone (PVPP) is a synthetic, insoluble polymer that can be added to white wines to improve the chemical stability of the final product by precipitating unstable low molecular weight phenolic compounds responsible for visual defects and undesirable flavor characteristics (e.g., excessive bitterness and/or astringency). The objective of this study was to characterize the effects of PVPP on the quality characteristics of Viognier wine when added pre- or post-fermentation as compared to an untreated control wine. Both PVPP-treated wines contained significantly lower concentrations of monomeric phenolics and browning pigments than the control wine (p≤0.05). The addition of PVPP prior to fermentation conferred protection against oxidation of the wine as measured by acetaldehyde concentration (p≤0.05). Analysis of the volatile aroma profile of each wine by headspace solid phase microextraction gas chromatographymass spectrometry (HS-SPME-GC-MS)revealed that the overarching aroma profiles of the PVPP-treated wines were significantly different from the control wine, but there was no difference between wines treated with PVPP pre-fermentation versus those treated post-fermentation. Specifically, statistically significant differences were observed in 9 of the 22 quantified aroma compounds, including those notably associated with the "stone fruit" aroma of Viognier. A negative correlation was identified between aroma compound concentration removal and the hydrophobicity of each compound, suggesting that the observed differences in aroma may be due to adsorption of aroma compounds by PVPP. The findings from this study present risks and benefits to wine quality upon treatment with PVPP at commercially recommended levels, and provide potentially valuable information for industrial wine producers.

Preparation of Eudragit S100-pullulan/hydroxypropyl-β-cyclodextrin complex-Eudragit S100 multilayer nanofiber film for resveratrol colon delivery

Cyclodextrin-based electrospun nanofibers are promising for encapsulating and preserving unstable compounds, but quick dissolution of certain nanofibers hinders their delivery application. In this study, hydroxypropyl-β-cyclodextrin (HPβCD) was used as an effective carrier of resveratrol (RSV) to obtain the RSV/HPβCD inclusion complex (HPIC), which was then incorporated into pullulan nanofibers. For enhancement of RSV release toward colon target, multilayer structure with a pullulan/HPIC film sandwiched between two layers of hydrophobic Eudragit S100 (ES100) nanofibers was employed. The relationship between the superiority of the ES100-pullulan/HPIC-ES100 film and its multilayer structure was verified. The intimate interactions of hydrogen bonds between two adjacent layers enhanced thermal stability, and the hydrophobic outer layers improved water contact resistance. According to release results, multilayer films also showed excellent colon-targeted delivery property and approximately 78.58 % of RSV was observed to release in colon stage. In terms of release mechanism, complex mechanism best described RSV colonic release. Additionally, ES100-pullulan/HPIC-ES100 multilayer films performed higher encapsulation efficiency when compared to the structures without HPIC, which further increased the antioxidant activity and total release amount of RSV. These results suggest a promising strategy for designing safe colonic delivery systems based on multilayer and HPIC structures with superior preservation for RSV.

Lithium Bromide-Promoted Formal C(sp3)-H Bond Insertion Reactions of β-Carbonyl Esters with Sulfoxonium Ylides to Synthesize 1,4-Dicarbonyl Compounds.

A LiBr-promoted formal C(sp3)-H bond insertion reaction between β-carbonyl esters and sulfoxonium ylides is established. This practical reaction has a wide range of substrate scope for both β-carbonyl esters and sulfoxonium ylides to give a variety of 1,4-dicarbonyl compounds with 43-94% yields. The reaction features transition-metal-free reaction conditions and exclusive C-alkylation chemselectivity. The use of bench-stable sulfoxonium ylides overcomes previous methods that require transition metal as catalysts and unstable diazo compounds or toxic haloketones as alkylation reagents.

Applicability of sodium butyrate preparations from a surgeon's and gastroenterologist's perspective.

In recent years, much has been written about the possibilities of using exogenous sodium butyrate in the prevention and treatment of gastrointestinal diseases, in prehabilitation, in peri- and postoperative treatment, as well as its local application. It became possible thanks to the development of a special formulation (microencapsulation technique) enabling the delivery of unstable butyrate compounds to the large intestine, where it is used primarily as a source of energy. It also plays a key role in maintaining body homeostasis by maintaining the integrity of the intestinal epithelium and stimulating the intestinal immune system. There is growing evidence of the effectiveness of sodium butyrate in various areas of health. The following article discusses the possibilities of using microencapsulated sodium butyrate in the prevention and treatment of gastrointestinal diseases from the perspective of a gastroenterologist and gastrointestinal surgeon.

Antibacterial, Anti-inflammatory properties and Therapeutic Benefits of Cardamom (Elettaria cardamomum)

Cardamom (Elettaria cardamomum) is a conventional fragrant plant for which a few pharmacological properties have been related. In this consider, the antibacterial movement of two cardamom extricates (natural product and seeds), wealthy in unstable compounds, against major periodontal pathogens was assessed. In addition, the capacity of the extricates to apply anti-inflammatory action was tried. Both cardamom natural product and seed extricates applied an antibacterial impact against Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Porphyromonas gingivalis, and Prevotella intermedia (least inhibitory concentrations: 0.5% [v/v], 0.25%, 0.062%, 0.125%, individually and least bactericidal concentrations: 1%, 0.25%, 0.062%, 0.25%, individually). The cell film of P. gingivalis was disturbed by a treatment with cardamom extricates proposing the bactericidal mode of activity. The extricates moreover restrained biofilm arrangement in spite of the fact that it related with a development decrease. Besides, the cardamom extricates altogether diminished the emission of IL-1β, TNF- α, and IL-8 by lipopolysaccharide-stimulated macrophages. Prove were brought that the anti- inflammatory movement may result from restraint of the NF-κB signaling pathway. This ponder is the to begin with to give prove that cardamom natural product and seed extricates through their antibacterial and anti-inflammatory properties may be helpful specialists of intrigued against periodontal diseases. Keywords: Cardamom; pharmacology; antibacterial; anti-inflammatory; antimicrobial, therapeutic.

Revolutionizing Knee Osteoarthritis Treatment: Innovative Self-Nano-Emulsifying Polyethylene Glycol Organogel of Curcumin for Effective Topical Delivery.

In the current study, self-nano-emulsifying (SNE) physically cross-linked polyethylene glycol (PEG) organogel (SNE-POG) as an innovative hybrid system was fabricated for topical delivery of water-insoluble and unstable bioactive compound curcumin (CUR). Response surface methodology (RSM) based on Optimal Design was utilized to evaluate the formulation factors. Solid fiber mechanism with homogenization was used to prepare formulations. Pharmaceutical evaluation including rheological and texture analysis, their mathematical correlations besides physical and chemical stability experiments, DSC study, in vitro release, skin permeation behavior, and clinical evaluation were carried out to characterize and optimize the SNE-OGs. PEG 4000 as the main organogelator, Poloxamer 188 (Plx188) and Ethyl Cellulose (EC) as co-gelator/nanoemulsifier agents, and PEG 400 and glycerin as solvent/co-emulsifier agents could generate SNE-POGs in PS range of 356 to 1410 nm that indicated organic base percentage and PEG 4000 were the most detrimental variables. The optimized OG maintained CUR stable in room and accelerated temperatures and could release CUR sustainably up to 72 h achieving high flux of CUR through guinea pig skin. A double-blind clinical trial confirmed that pain scores, stiffness, and difficulty with physical function were remarkably diminished at the end of 8 weeks compared to the placebo (71.68% vs. 7.03%, 62.40% vs. 21.44%, and 45.54% vs. 8.66%, respectively) indicating very high efficiency of system for treating knee osteoarthritis. SNE-POGs show great potential as a new topical drug delivery system for water-insoluble and unstable drugs like CUR that could offer a safe and effective alternative to conventional topical drug delivery system.