Monocarboxylic Acids Research Articles

Optimizing malathion biodegradation by Bacillus cereus via a design of experiment framework

Bacteria have effectively been employed to biodegrade pesticides, and current research was envisioned to investigate malathion degradation by Bacillus sp. isolated from field soils. About 30.87–72.25% biodegradation was observed after 96 h with the Bacillus sp. when malathion was used as sole carbon, which increased to 45.77–100% after 240 h at initial malathion concentrations of 0.005–0.1%, respectively. The influence of co-substrates, pH, pesticide concentration, rpm, temperature, and inoculum doses were examined to further optimize malathion biodegradation, and the effect of these factors was investigated by the Taguchi design of experiments (DOE). The optimal biodegradation conditions were obtained at 0.1% (w/v), glucose and yeast extract, pH − 7, temperature − 40 °C, malathion concentration − 0.03% (v/v), agitation − 150 rpm, and inoculum dose − 2% (v/v). The biodegradation rate was boosted to 98% at optimal conditions within 36 h. Malathion degradation was confirmed by ultra-high performance liquid chromatography (UHPLC) studies, followed by the elucidation of three different biodegradation/transformation pathways through GC/MS analysis. Biodegradation analysis of malathion by GC/MS confirmed the formation of a monocarboxylic acid, malaoxon, mercaptosuccinic acid, and phosphorus moiety. These findings unequivocally corroborate that Bacillus sp. inherits immense potential for biodegrading malathion at a wide range of environmental conditions and provides a workable solution for bioremediation of malathion.

Eplerenone, a mineralocorticoid receptor inhibitor, reduces cirrhosis associated changes of hepatocyte glucose and lipid metabolism

BackgroundRecent studies suggest a contribution of intrahepatic mineralocorticoid receptor (MR) activation to the development of cirrhosis. As MR blockade abrogates the development of cirrhosis and hypoxia, common during the development of cirrhosis, can activate MR in hepatocytes. But, the impact of non-physiological hepatic MR activation is unknown. In this study, we investigate the impact of hypoxia-induced hepatocyte MR activation as a relevant factor in cirrhosis.MethodsRNA sequencing followed by gene ontology term enrichment analysis was performed on liver samples from rats treated for 12 weeks with or without CCl4 and for the last four weeks with or without eplerenone (MR antagonist). We investigated if these changes can be mimicked by hypoxia in a human hepatocyte cell line (HepG2 cells) and in primary rat hepatocytes (pRH). In order to evaluate the functional cellular importance, hepatocyte lipid accumulation, glucose consumption, lactate production and mitochondrial function were analyzed.ResultsIn cirrhotic liver tissue genes annotated to the GOterm “Monocarboxylic acid metabolic process” (PPARα, PDK4, AMACR, ABCC2, Lipin1) are downregulated. This effect is reversed by the MR antagonist eplerenone in vivo. The alterations are partially mimicked by hypoxia in rat and human hepatocytes in tissue culture. Furthermore, the reduction of mRNA and protein expression of PPARα, PDK4, AMACR, ABCC2 and Lipin1 during hypoxia is prevented by eplerenone in rat and human hepatocytes. Aldosterone, the endogenous MR agonist, did not affect the expression of those proteins in hepatocytes. As those proteins are key regulators of hepatocyte energy homeostasis, we analyzed if hypoxia affected glucose consumption, lactate production and lipid accumulation in HepG2 cells in a MR-mediated manner. All three parameters were affected by hypoxia and were partially normalized by eplerenone.ConclusionOur findings suggest that non-physiological MR activation plays a role in the dysregulation of glucose and lipid metabolism in hepatocytes. This leads to an increase in apoptosis, probably resulting in a proinflammatory micromilieu of the hepatic tissue. The enhanced deposition of extracellular matrix contributes to the development of cirrhosis. Therefore, MR antagonists may have therapeutic potential in the treatment of early stages of liver disease due to their direct action in the liver.

Comprehensive analysis of lysine lactylation and its potential biological significance in clear cell renal cell carcinoma

BackgroundClear cell renal cell carcinoma (ccRCC) is a common histological subtype of malignant renal neoplasm. Protein lysine lactylation (Kla) plays a crucial role in tumor metabolic reprogramming. However, little is known regarding the distribution and potential biological functions of Kla in ccRCC. This study aimed to systematically investigate the role of Kla in ccRCC.MethodsA total of 12 ccRCC samples were collected from 6 patients. Western blotting was performed to determine the trend of Kla-modified proteins in ccRCC. Liquid chromatography–tandem mass spectrometry was used to quantitatively analyze Kla in ccRCC. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and protein–protein interaction (PPI) network analyses were conducted to clarify the biological functions and interactional relationships of differentially lactylated proteins (DLPs).ResultsIn total, 239 DLPs, including 441 lactylated sites, were identified by comparing ccRCC tissues with adjacent normal tissues. Kla-related enzymes have a higher affinity for alanine than for other amino acid residues in ccRCC. Subcellular localization analysis revealed that most DLPs were localized in the cytoplasm and mitochondria. GO enrichment analysis showed that most of the DLPs were enriched in metabolism-associated biological processes, including the purine ribonucleotide, monocarboxylic acid, ribonucleoside triphosphate, purine nucleoside triphosphate, and ATP metabolic processes. KEGG analysis indicated that most DLPs were also enriched in metabolism-related pathways, including glycolysis, amino acid (valine, leucine, and isoleucine) degradation, pyruvate metabolism, fatty acid degradation, and the citrate cycle. The top 20 hub proteins were screened from the PPI network based on their degree ranks.ConclusionsThis study revealed the role of Kla in ccRCC, which will extend our understanding of the potential molecular mechanisms underlying ccRCC formation and progression. These key Kla-modified proteins may be promising therapeutic targets for the treatment of ccRCC. However, further molecular experiments are required to validate these findings.

Controlling the heterogeneous catalysis of zirconium clusters within a porous SBA-15 scaffold

Metal-organic frameworks (MOFs) with Zr-based secondary building units (SBUs) have shown promise as materials for the catalytic degradation of chemical warfare agents (CWAs). The Zr-based SBU within the MOF has been previously determined to be the active site for catalytic hydrolysis reactions within these materials. However, MOF structure dictates access to the SBU active sites with microporous MOFs showing catalysis solely on the surface of the particles of the MOF and MOFs with analogous SBUs exhibiting different reaction rates under the same reaction conditions. The multitude of variables inherent to MOF structures (e.g. pore size, pore structure, connectivity, crystal size, functional groups, defects, and monocarboxylic acid modulators (MCAMs) used in synthesis) complicate the fundamental understanding of the SBU's reactivity in the hydrolysis reaction independent of topological constraints. In this work, we have explored the catalytic activity of a simplified SBU system consisting of Zr6 and Zr12 clusters decorated with MCAMs varying in size and functionality to simulate the chemical environment of the SBU within the MOF structure. The zirconium clusters were then supported on mesoporous silica (SBA-15) functionalized with either sulfuric or phosphoric acid groups that bind to the zirconium nodes, covalently tethering the clusters to the silica support. These novel porous materials were designed to mimic the porous nature of the MOF structure to determine the effect on hydrolysis reactivity. The final silica-bound zirconium clusters showed enhanced reactivity towards the hydrolysis of dimethyl nitrophosphate (DMNP), a nerve agent simulant, under buffered conditions compared to the bare Zr clusters and showed key differences in the catalytic activity based on the chemical environment imparted by both the MCAM and the modified support. In addition, the use of an acid-modified silica scaffolding allowed for the incorporation of adjacent amine moieties on the SBA-15 support to facilitate hydrolysis of DMNP under neutral aqueous conditions, a benefit over typical Zr-based MOF catalysts that require a buffer for appreciable reactivity.

Comparative Transcriptome Analysis Reveals the Impact of a High-Fat Diet on Hepatic Metabolic Function in Tilapia (Oreochromis niloticus).

Hepatic steatosis is prevalent among cultured fish, yet the molecular mechanisms remain incompletely understood. This study aimed to assess changes in hepatic metabolic function in tilapia and to explore the underlying molecular mechanisms through transcriptomic analyses. Tilapia were allocated into two groups: a normal control (Ctr)-fed group and a high-fat diet (HFD)-fed group. Serum biochemical analyses revealed that HFD feeding led to liver damage and lipid accumulation, characterized by elevated levels of glutamic-pyruvic transaminase (GPT), glutamic-oxaloacetic transaminase (GOT), triglycerides (TGs), and total cholesterol (TC). Transcriptome analysis showed that 538 genes were significantly downregulated, and 460 genes were significantly upregulated in the HFD-fed fish. Gene Ontology (GO) enrichment analysis showed that these differentially expressed genes (DEGs) were apparently involved in the lipid metabolic process and monocarboxylic acid metabolic process. Meanwhile, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicated significant alterations in pathways of steroid biosynthesis, porphyrin metabolism, terpenoid backbone biosynthesis, and retinol metabolism after HFD feeding. Additionally, results from Gene Set Enrichment Analysis (GSEA) revealed that gene expression patterns in pathways including oxidative phosphorylation, protein export, protein processing in the endoplasmic reticulum, and ribosome biogenesis were positively enriched in the HFD-fed tilapia. These findings provide novel insights into the mechanisms underlying HFD-induced hepatic dysfunction in fish, contributing to the optimization of feeding strategies in aquaculture.

Defect-controlled confined growth of nano-MOFs to prepare materials with hierarchical micro/mesoporous structures for efficient CO2 capture

In recent years, nanoporous materials with special structure have been widely used in various fields. In view of the poor stability of MOFs materials and the poor mass transfer ability, in this study, we developed a simple method to restrict the growth of UiO-66-NH2 crystals in hollow silica by “vacuum evaporation” strategy, different kinds of acid regulators were introduced, to obtain a composite material with hierarchical pore structure. By characterizing the physical chemistry and microstructure of the composite adsorbent, and calculating the structural defects under different acid regulation, the adsorption and desorption performance and stability of the adsorbent for CO2 were comprehensively investigated. The mechanism of action on CO2 was further analyzed by in-situ infrared and other techniques. The results show that the change of coordination environment and coordination rate caused by the competition of organic acids, which increases the defects and reduces the nucleation and aggregation effect of UiO-66-NH2, promotes the formation of hierarchical pore structure of the composites. Among them, benzoic acid is the best regulating monocarboxylic acid, which makes UiO-66-NH2 have good dispersion in the cavity and suitable crystal size. The specific surface area of the composite material is 717.96 m2 g−1. At the same time, due to its excellent CO2 adsorption capacity (3.35 mmol g−1) at 298 K and 1.06 bar, it is 48.07 % higher than the original UiO-66-NH2. In order to accomplish the goal of effective CO2 adsorption performance of composites, this study offers a novel approach for the synthesis and modification of MOFs-based composites.

Strategic Defect Engineering Enabled Efficient Oxygen Evolution Reaction in Reconstructed Metal‐Organic Frameworks

AbstractMetal‐organic frameworks (MOFs) have emerged as promising pre‐catalysts for oxygen evolution reaction (OER) due to their marvelous structural reconstruction process in strongly alkaline media. However, targeting design MOF structures to achieve excellent OER performance of reconstructed products is a challenge. Here, a strategic defect engineering is used to promote the OER performance of reconstructed products. Briefly, modified linkers with monocarboxylic acids (ferrocene carboxylic acid, FcCA) are incorporated into MOF (NiBDC‐FcCA), leading to its stepwise reconstruction into Fe‐doped Ni(OH)2 and NiOOH during the OER process, with the oxygen vacancy and strategic doping of metal Fe persisting throughout the multi‐step reconstruction. Benefiting from the synergistic interaction of oxygen vacancies and Fe doping, NiBDC‐FcCA delivers the extremely enhanced current density at 1.6 V versus reversible hydrogen electrode by ≈9 times compared with that of NiBDC. Moreover, the optimized NiBDC‐FcCA/Fe foam exhibits excellent OER catalytic activity and stability with a low overpotential of 250 mV at 200 mA cm−2 and negligible activity decay after 1200 h at 1 A cm−2. Density function theory calculations reveal that Fe doping weakens the interaction of oxygen intermediate with Ni sites, favoring the formation of OOH* to accelerate the OER process.

Comparative Analysis of Hepatic Gene Expression Profiles in Murine and Porcine Sepsis Models.

Sepsis remains a huge unmet medical need for which no approved drugs, besides antibiotics, are on the market. Despite the clinical impact of sepsis, its molecular mechanism remains inadequately understood. Recent insights have shown that profound hepatic transcriptional reprogramming, leading to fatal metabolic abnormalities, might open a new avenue to treat sepsis. Translation of experimental results from rodents to larger animal models of higher relevance for human physiology, such as pigs, is critical and needs exploration. We performed a comparative analysis of the transcriptome profiles in murine and porcine livers using the following sepsis models: cecal ligation and puncture (CLP) in mice and fecal instillation (FI) in pigs, both of which induce polymicrobial septic peritonitis, and lipopolysaccharide (LPS)-induced endotoxemia in pigs, inducing sterile inflammation. Using bulk RNA sequencing, Metascape pathway analysis, and HOMER transcription factor motif analysis, we were able to identify key genes and pathways affected in septic livers. Conserved upregulated pathways in murine CLP and porcine LPS and FI generally comprise typical inflammatory pathways, except for ER stress, which was only found in the murine CLP model. Conserved pathways downregulated in sepsis comprise almost exclusively metabolic pathways such as monocarboxylic acid, steroid, biological oxidation, and small-molecule catabolism. Even though the upregulated inflammatory pathways were equally induced in the two porcine models, the porcine FI model more closely resembles the metabolic dysfunction observed in the CLP liver compared to the porcine LPS model. This comprehensive comparison focusing on the hepatic responses in mouse CLP versus LPS or FI in pigs shows that the two porcine sepsis models generally resemble quite well the mouse CLP model, with a typical inflammatory signature amongst the upregulated genes and metabolic dysfunction amongst the downregulated genes. The hepatic ER stress observed in the murine model could not be replicated in the porcine models. When studying metabolic dysfunction in the liver upon sepsis, the porcine FI model more closely resembles the mouse CLP model compared to the porcine LPS model.

Computational analysis of diameter eccentricity based and hyper diameter eccentricity based indices for linear saturated monocarboxylic acids

Chemical graph theory deals with chemical graphs, which are used to represent chemical systems. Topological indices of molecular graphs are an important area of research in chemical graph theory. These indices are numerical values associated with compounds that aim to establish connections between chemical structures and physical attributes, chemical reactivity, and biological activity. Many graph polynomials have been proposed to compute various topological indices. Quantitative structure-property relationship (QSPR) analysis of chemical compounds involves several regression methods that rely on these topological indices. In this article, we utilize the newly introduced DƐ-polynomial to calculate the eccentricitybased indices such as the diameter eccentricity based and hyper diameter eccentricity based index values for nineteen linear saturated monocarboxylic acids. Quantitative structureproperty relationship (QSPR) analysis is also performed for the seven thermodynamic properties of monocarboxylic acids. The relationship between thermodynamic properties and topological indices is explored using linear, quadratic and cubic regression models. The best fit curvilinear regression models were determined based on the R2 and RMSE values of the models. To further investigate the statistical significance of our models, we also conducted chi-square goodness-of-fit tests to identify the best fit models.

A novel advanced reduction process for the reduction of Cr(VI): Assistance of microbial metabolites

Advanced reduction processes (ARPs) have become hotspot because of their fast and efficient features in pollutant treatment. In this study, a novel ARP was raised through the assistance of biological wastewater degradation solutions (PDs), to completely reduce Cr(VI). Enterobacter cloacae YN-4, which could completely degrade 1500 mg/L phenol within 72 h, was isolated and identified. While, the content of organic acids and their derivatives in PDs was extremely high (74.76 %). After the combination of PDs with Fe(III) and UV, 10 mg/L Cr(VI) was completely reduced within 66 min, whose reduction rate of Cr(VI) was stable at various concentrations (10–100 mg/L), which was applicable on electroplating wastewater. In addition, Cr(VI) could be reduced stably (71.63 %) after 10 cycles. Compared with the reported ARPs, herein, the components was complex, which was firstly proposed that simultaneous action of polycarboxylic acids, monocarboxylic acids, amino acids and alcohols could promote and ensure the stable reduction of Cr(VI). Among them, the multispecies radicals·CO2- and·O2- generated in PDs were combined with Fe(II), to co-reduce Cr(VI). This strategy produces a wide variety of radicals, which can provide an alternative pathway for remediation of various heavy metals and organic pollutants.

High-Throughput RPLC-MS/MS Quantification of Short- and Medium-Chain Fatty Acids.

Short- and medium-chain fatty acids (SMCFA) are monocarboxylic acids with a carbon chain length of 1-12 carbon atoms. They are mainly produced in humans by the gut microbiota, play crucial metabolic roles, are vital for intestinal health, and have multifaceted impact on immune and neurological functions. Accurate detection and quantification of SMCFA in different human biofluids is achieved using 3-nitro phenylhydrazine (3-NPH) derivatization of the free fatty acids followed by reverse phase liquid chromatography (RPLC) separation and detection by tandem mass spectrometry (MS/MS). Here, we describe the simultaneous measurement of 14 SMCFA and lactate in detail. All 3-NPH-SMCFA-hydrazones are separated in less than 5min with an 8-min total run time (injection-to-injection). Linear dynamic range over 0.1-500μM is achieved for most SCFAs, while it is 0.05-100μM for MCFAs. Validation of the procedure depicts good linearity (R2>0.98) and repeatability (CV≤20%). The lower limit of detection (LLOD) is 10-30nM. The lower limit of quantification (LLOQ) is 50-100nM for most analytes, while it is 0.5μM for acetate. In conclusion, the method offers several benefits compared to alternative methods regarding throughput, selectivity, sensitivity, and robustness.

Enhancing nutrient bioavailability in distillery wastewater through electrochemical oxidation for microalgal growth: Insights on biomass yield, nutrient utilisation, and VFA-assisted carbon capture

Two-stage treatment of distillery wastewater (DWW) via electrochemical oxidation (EO) using Ti-RuO2 anodes (35 cm2 area) followed by mixotrophic microalgal treatment was investigated. In the first-stage, EO of DWW has improved the bioavailability of nitrogen and phosphorus at 3.95–5.14 mg/Ah and 0.43–1.02 mg/Ah, respectively, which had strong correlation with current density. EO also reduced ∼30 % TOC, 53 % COD and ∼44 % TN. In the second-stage, the ability of a novel microalgae, Asterarsys quadricellulare to mitigate the toxicity of electrochemically oxidised DWW (EO-DWW) while utilising the nutrients effectively was investigated. The mixotrophic algal growth effectively utilised 85 % phosphate and 91 % nitrate present in EO-DWW at a corresponding growth rate of 0.73 d−1. The algal biomass was found to have ∼15 % carbohydrates, ∼12 % lipids and ∼33 % proteins. Subsequently, a bench-scale bubble column photobioreactor investigation was carried out to understand the carbon dynamics during the growth of Asterarsys quadricellulare. The metabolic uptake of monocarboxylic volatile fatty acids (VFA) and nitrate were found to release OH− ions, which eventually helped in dissolving CO2 in the reactor through a diffusion-limited process. The total energy spent in bench-scale EO system was 840 kWh (3024 kJ) per L of DWW, and the energy recovery potential of second-stage algal reactor was ∼8.7 %. The microtoxicity experiments with Alivibrio fischeri revealed that two-stage treated DWW was found to be safe for reuse as the microalgal growth has abated the toxicity of EO-DWW.

Transcriptomic Approach Reveals Contrasting Patterns of Differential Gene Expression during Tannin Biodegredation by Aspergillus tubingensis in Liquid and Solid Cultures

Tannins, one of the most common anti-nutritional factors in feed, can be effectively degraded by various enzymes secreted by Aspergillus tubingensis (A. tubingensis). The cultivation method of fungi significantly impacts gene expression, which influences the production of enzymes and metabolites. In this study, we analyzed the tannin biodegredation efficiency and the transcriptomic responses of A. tubingensis in liquid and solid cultures with tannin added. The observed morphology of A. tubingensis resembled typical fungal hyphae of mycelium submerged and grown in liquid cultures, while mainly spore clusters were observed in solid cultures. Furthermore, the tannin biodegredation efficiency and protein secretion of A. tubingensis in liquid cultures were significantly higher than in solid cultures. Additionally, 54.6% of the 11,248 differentially expressed genes were upregulated in liquid cultures, including AtWU_03490 (encoding ABC multidrug transporter), AtWU_03807 (ribonuclease III), AtWU_10270 (peptidyl-tRNA hydrolase), and AtWU_00075 (arabinogalactan endo-1,4-beta-galactosidase). Functional and gene ontology enrichment analyses indicated upregulation in processes including oxidation reduction, drug metabolism, and monocarboxylic acid metabolism. Overall, this study provides insight into the transcriptomic response to tannin biodegradation by A. tubingensis in different cultures and reveals that liquid cultures induce greater transcriptomic variability compared to solid cultures.

Crystallinity Reconstruction of Squid-Pen Chitosan into Mechanically Robust and Multifunctional Bionanocomposite Food Packaging Film.

First, we explore the effect of bioacids on the film processing of preprocessed, i.e., deacetylated, chitosan (d-chitosan with molecular weight of 1,000,000 kDa), using monocarboxylic acid (acetic acid), dicarboxylic acid (malic acid), and tricarboxylic acid (citric acid) as model weak acidic solvents to destabilize the hydrogen bonding and transform crystal structures into film. Second, we investigate the chemical and physical toughening effect in the bionanocomposite film composed of cross-linkable multicarboxilic acid, i.e., succinic acid (SA). In doing so, the addition of glycerol as a plasticizer can increase polymer chain mobility, making the biocomposite film more ductile and flexible. The addition of CNC also enhances the tensile strength (41.6%), swelling (43.47%), and oxygen barrier properties (38.81%), as well as significantly improves UV light barrier. The excellent antibacterial properties (99.9% efficiency against S. aureus and K. pneumoniae) of the prepared biocomposite films are found to be independent of the presence of glycerol or CNC. Third, the development of film processability under an industrially relevant process is also demonstrated by doctor blade method. It is found that film processability of the squid-pen's chitosan bionanocomposite can straightforwardly be compatible with and improvable in the presence of poly(vinyl alcohol) employed as a model biodegradable processing aid.

Volume Effects in Interactions between L-Histidine and Pyridine Monocarboxylic Acid Isomers in an Aqueous Buffer Solution

Volume Effects in Interactions between L-Histidine and Pyridine Monocarboxylic Acid Isomers in an Aqueous Buffer Solution

Functionalized Adenine-based Receptors for Monocarboxylic Acids’ Recognition

: Three receptors 1-3, built on adenine, have been synthesized, structurally characterized, and successfully employed for the recognition of monocarboxylic acids. The adenine- based receptors 1-3 have been found to bind monocarboxylic acids via the Hoogsteen (HG) binding site or the Watson-Crick (WC) binding site and form 1:1 complexes in CHCl3. Detailed binding of the receptors 1-3, in the presence of the monocarboxylic acids, corroborates that there is a distinct propensity of the HG site for aromatic carboxylic acids, for example, (S)-mandelic acid and benzoic acid. Aliphatic acids, for example, propanoic acid and rac-lactic acid, on the other hand, prefer to bind at the WC site. The monocarboxylic acid bindings to 1-3 were examined by UV–Vis, fluorescence, and 1H NMR spectroscopic methods, and DFT study.

γ-Lactones in Canadian high arctic aerosols: Tracers for the oxidation of unsaturated fatty acids and intramolecular esterification of γ-hydroxyacids during polar sunrise

In this study, we detected for the first time a series of γ-lactones (C7-C16) isolated from Canadian high arctic aerosols collected from late February to June as the sun rises from below the horizon to the maximum. γ-Lactones were identified and quantified by GC-MS utilizing the fragment ion (m/z 85) of [C4H5O2]+. Their molecular distributions showed the predominance of C9 species (on average, 25 pg/m3) followed by C10, C8, C11, C12, C16, C15, and C7. The odd-carbon numbered γ-lactones such as C9 and C11 are produced by the oxidation of oleic (Δ9C18:1) and eicosanoic (Δ9C20:1) acids, respectively, to monocarboxylic acids in the atmosphere, followed by the subsequent oxidation to positional isomers of hydroxy acids and intramolecular esterification of γ-hydroxy acids. Unsaturated fatty acids, plausible sources of the γ-lactones, can originate from marine phytoplankton and terrestrial vegetation via long-range atmospheric transport to the Arctic. Series of ω-oxoacids were also detected with the predominance of C9 species, supporting the photochemical oxidation of biogenic unsaturated fatty acids in the Arctic atmosphere after polar sunrise and/or during the long-range transport to the Arctic.

Harnessing a Pd4 Water-Soluble Molecular Capsule as a Size-Selective Catalyst for Targeted Oxidation of Alkyl Aromatics.

Molecular hosts with functional cavities can emulate enzymatic behavior through selective encapsulation of substrates, resulting in high chemo-, regio-, and stereoselective product formation. It is still challenging to synthesize enzyme-mimicking hosts that exhibit a narrow substrate scope that relies upon the recognition of substrates based on the molecular size. Herein, we introduce a Pd4 self-assembled water-soluble molecular capsule [M 4 L 2] (MC) that was formed through the self-assembly of a ligand L (4',4‴'-(1,4-phenylene)bis(1',4'-dihydro-[4,2':6',4″-terpyridine]-3',5'-dicarbonitrile)) with the acceptor cis-[(en)Pd(NO3)2] [en = ethane-1,2-diamine] (M). The molecular capsule MC showed size-selective recognition towards xylene isomers. The redox property of MC was explored for efficient and selective oxidation of one of the alkyl groups of m-xylene and p-xylene to their corresponding toluic acids using molecular O2 as an oxidant upon photoirradiation. Employing host-guest chemistry, we demonstrate the homogeneous catalysis of alkyl aromatics to the corresponding monocarboxylic acids in water under mild conditions. Despite homogeneous catalysis, the products were separated from the reaction mixtures by simple filtration/extraction, and the catalyst was reused. The larger analogues of the alkyl aromatics failed to bind within the MC's hydrophobic cavity, resulting in a lower/negligible reaction outcome. The present study represents a facile approach for selective photo-oxidation of xylene isomers to their corresponding toluic acids in an aqueous medium under mild conditions.

Identification of Fatty Acids, Amides and Cinnamic Acid Derivatives in Supercritical-CO2 Extracts of Cinnamomum tamala Leaves Using UPLC-Q-TOF-MSE Combined with Chemometrics.

Cinnamomum tamala leaf (CTL), also known as Indian bay leaf, is used all over the world for seasoning, flavoring, and medicinal purposes. These characteristics could be explained by the presence of several essential bioactive substances and lipid derivatives. In this work, rapid screening and identification of the chemical compounds in supercritical (SC)-CO2 extracts of CTL by use of UPLC-Q-TOF-MSE with a multivariate statistical analysis approach was established in both negative and positive mode. A total of 166 metabolites, including 66 monocarboxylic fatty acids, 52 dicarboxylic fatty acids, 27 fatty acid amides, and 21 cinnamic acid derivatives, were tentatively identified based on accurate mass and the mass spectrometric fragmentation pattern, out of which 142 compounds were common in all SC-CO2 extracts of CTL. Further, PCA and cluster hierarchical analysis clearly discriminated the chemical profile of analyzed extracts and allowed the selection of SC-CO2 extract rich in fatty acids, fatty acid amides, and other bioactive constituents. The result showed that the higher number of compounds was detected in CTL4 (300 bar/55 °C) extract than the other CTL extracts. The mono- and di-carboxylic fatty acids, fatty acid amides, and cinnamic acid derivatives were identified in CTL for the first time. UPLC-Q-TOF-MSE combined with chemometric analysis is a powerful method to rapidly screen the metabolite profiling to justify the quality of CTL as a flavoring agent and in functional foods.

Physical and Chemical Characterization of Aerosols Produced from Experimentally Designed Nicotine Salt-Based E-Liquids.

Nicotine salt-based e-liquids deliver nicotine more rapidly and efficiently to electronic nicotine delivery system (ENDS) users than freebase nicotine formulations. Nicotine salt-based products represent a substantial majority of the United States ENDS market. Despite the popularity of nicotine salt formulations, the chemical and physical characteristics of aerosols produced by nicotine salt e-liquids are still not well understood. To address this, this study reports the harmful and potentially harmful constituents (HPHCs) and particle sizes of aerosols produced by laboratory-made freebase nicotine and nicotine salt e-liquids. The nicotine salt e-liquids were formulated with benzoic acid, citric acid, lactic acid, malic acid, or oxalic acid. The nicotine salt aerosols had different HPHC profiles than the freebase nicotine aerosols, indicating that the carboxylic acids were not innocent bystanders. The polycarboxylic acid e-liquids containing citric acid, malic acid, or oxalic acid produced higher acrolein yields than the monocarboxylic acid e-liquids containing benzoic acid or lactic acid. Across most PG:VG ratios, nicotine benzoate or nicotine lactate aerosols contained the highest nicotine quantities (in %) and the highest nicotine yields (per milligram of aerosol). Additionally, the nicotine benzoate and nicotine lactate e-liquids produced the highest carboxylic acid yields under all tested conditions. The lower acid yields of the citric, malic, and oxalic acid formulations are potentially due to a combination of factors such as lower transfer efficiencies, lower thermostabilities, and greater susceptibility to side reactions because of their additional carboxyl groups serving as new sites for reactivity. For all nicotine formulations, the particle size characteristics were primarily controlled by the e-liquid solvent ratios, and there were no clear trends between nicotine salt and freebase nicotine aerosols that indicated nicotine protonation affected particle size. The carboxylic acids impacted aerosol output, nicotine delivery, and HPHC yields in distinct ways such that interchanging them in ENDS can potentially cause downstream effects.