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Development of new organic synthetic methods fascinating the researchers which facilitating the increasing demands of the modern society, environmental friendly with high efficiency and low cost. The introduction of chromophores in an organic molecules facilitating intersystem crossing (ISC) to harvest both singlet and triplet excitons is also currently demanding field. We report a facile synthesis of symmetrical azines from carbonyl compounds and hydrazine hydrate with carboxylic acid esters as catalyst in methanol. This reaction presents a condensation of primary amino groups in hydrazine hydrate and carbonyl compounds took place simultaneously in a very short refluxing time. The prepared azines 1–10 were structurally analysed by various analytical techniques such as LC-MS1, H NMR13, C NMR, UV-Vis, FTIR and single crystal X-ray diffraction. Photoluminescence properties of prepared azines were recorded in CCl4 at 1 × 10−3 M and excitation range from 329 to 362 nm. The photoluminescence analysis results revealed that compounds 1–10 (except 8) were showed delayed fluorescence and 8 was showed fluorescence property. The photophysical properties of compounds 1–10 such as electron density and band gap energies was calculated by density function theory. This results revealed that the intra-molecular charge transfer occurs within the azines. The azine function in the azines enabling intersystem crossing hence, it is showing phosphorescence. [ABSTRACT FROM AUTHOR]

There is a growing demand for herbicides that are more effective than conventional ones yet less harmful to ecosystems. In light of this, this study aimed to synthesize esters from phenols and phenoxyacetic acid, using compounds with known phytotoxic potential as starting materials. Phenoxyacetic acid was first synthesized and then utilized in the synthesis of seven esters through Steglich esterification, employing N,N'-dicyclohexylcarboimide and N,N-dimethylpyridin-4-amine in the presence of phenols (thymol, vanillin, eugenol, carvacrol, guaiacol, p-cresol, and β-naphthol), yielding esters 1–7. All synthesized compounds were characterized using mass spectrometry, 1H, and 13C NMR. These compounds were tested for phytotoxicity to evaluate their effects on the germination and root development of Sorghum bicolor and Lactuca sativa seeds, and for the induction of alterations in the mitotic cycle of meristematic cells of L. sativa roots. Esters 1, 3, 4, and 5 exhibited the most significant phytotoxic activity in both L. sativa and S. bicolor. Alterations in the mitotic index and frequency of chromosomal alterations in L. sativa roots revealed the cytotoxic, genotoxic effects, and the aneugenic mode of action of the tested molecules. These findings suggest that these compounds could serve as inspiration for the synthesis of new semi-synthetic herbicides. [ABSTRACT FROM AUTHOR]

Carboxylesterases serve as potent biocatalysts in the enantioselective synthesis of chiral carboxylic acids and esters. However, naturally occurring carboxylesterases exhibit limited enantioselectivity, particularly toward ethyl 3-cyclohexene-1-carboxylate (CHCE, S1), due to its nearly symmetric structure. While machine learning effectively expedites directed evolution, the lack of models for predicting the enantioselectivity for carboxylesterases has hindered progress, primarily due to challenges in obtaining high-quality training datasets. In this study, we devise a high-throughput method by coupling alcohol dehydrogenase to determine the apparent enantioselectivity of the carboxylesterase AcEst1 from Acinetobacter sp. JNU9335, generating a high-quality dataset. Leveraging seven features derived from biochemical considerations, we quantitively describe the steric, hydrophobic, hydrophilic, electrostatic, hydrogen bonding, and π-π interaction effects of residues within AcEst1. A robust gradient boosting regression tree model is trained to facilitate stereodivergent evolution, resulting in the enhanced enantioselectivity of AcEst1 toward S1. Through this approach, we successfully obtain two stereocomplementary variants, DR3 and DS6, demonstrating significantly increased and reversed enantioselectivity. Notably, DR3 and DS6 exhibit utility in the enantioselective hydrolysis of various symmetric esters. Comprehensive kinetic parameter analysis, molecular dynamics simulations, and QM/MM calculations offer insights into the kinetic and thermodynamic features underlying the manipulated enantioselectivity of DR3 and DS6. Carboxylesterases catalyze the enantioselective synthesis of chiral carboxylic acids and esters but exhibit limited enantioselectivity, particularly toward ethyl 3-cyclohexene-1- carboxylate (CHCE). Here, the authors establish a high-throughput method to generate a high-quality dataset for carboxylesterase AcEst1 from Acinetobacter sp. JNU9335 using CHCE as the substrate, use it to train a machine learning predictor and design two stereocomplementary mutants to synthesize both enantiomers of chiral CHCE. [ABSTRACT FROM AUTHOR]

There is need for advancing minimally invasive diagnostic techniques for sex differentiation at early life-stage classes in sea turtles. The objectives of this study were to determine whether there are sex-specific effects on the metabolome of the loggerhead sea turtle (Caretta caretta) and to identify potential biomarkers for sex classification at early life-stage classes (50 post-hatchling and 50 juvenile). Comprehensive analyses including plasma chemistry (n = 100) and untargeted (n = 48) metabolomic analyses were performed. Unlike with plasma chemistry analytes, there were significant differences in the metabolomic profiles between sexes. Nine metabolites differed significantly between sexes, with several metabolites deserving greater attention as potential biomarkers: C22H32O6 and pantothenic acid was higher in females than in males, and carboxylic acid ester (C10H16O5), 1-methylhistidine and C7H14N2O7 was higher in males than females. These differences remained constant both across and within the same life-stage class. This work identified a discernible effect on the metabolic profile based on sex of loggerhead sea turtles and it suggests that these metabolites and/or their ratios could serve as potential biomarker candidates for sex classification in this species. This study demonstrates a distinct metabolomic profile between male and female loggerhead turtles at different physiological stages (posthatchling and juvenile animals) and proposes biomarkers for sex classification. [ABSTRACT FROM AUTHOR]

Coffee is one of the most highly valued, consumed and comercialized foods in the world. Due to its considerable importance, it has become the target of numerous adulterations. Detecting a possible adulteration and the presence of additional adulterants in coffee has become an issue of great concern mainly because the compounds used as adulterants exhibit physical features very similar to ground roasted coffee. Aiming to overcome these difficulties, this work reports the development and application of a relatively faster, highly effective and reliable method for the detection and identification of adulterations in roasted coffee through the analysis of the composition of the volatile fraction in the presence of adulterants such as rice, corn, soybeans and barley. The proposed method was based on gas chromatography coupled with mass spectrometry (GC–MS) and chemometric tools. The application of the method led to the exclusive identification of many compounds in the volatile fraction of the adulterants investigated. The adulterants, despite having compounds similar to coffee, differed in terms of their volatile profiles, and consisted mainly of hydrocarbons, aldehydes, esters and carboxylic acids. Among all the compounds identified, five compounds were found to be the main determinants of adulteration: 2-furanmethanol-acetate, 2-methoxy-4-vinylphenol, 5-methyl-2-furancarboxaldehyde, 2-furanmethanol and glycerol-1,2-diacetate. [ABSTRACT FROM AUTHOR]

Alkoxycarbonylation reactions are common in the chemical industry, yet process sustainability is limited by the inefficient utilization of CO. In this study, we address this issue and demonstrate that significant improvements can be achieved by adopting a heterogeneously catalyzed process, using a Ru/NbOx catalyst. The Ru/NbOx catalyst enables the direct synthesis of methyl propionate, a key industrial commodity, with over 98% selectivity from CO, ethylene and methanol, without any ligands or acid/base promoters. Under ambient CO pressure, a high CO utilization efficiency (336 mmolestermolCO−1h−1) is achieved. Mechanistic investigations reveal that CO undergoes a methoxycarbonyl (COOCH3) intermediate pathway, attacking the terminal carbon atom of alkene and yielding linear esters. The origins of prevailing linear regioselectivity in esters are revealed. The infrared spectroscopic feature of the key COOCH3 species is observed at 1750 cm−1 (C=O vibration) both experimentally and computationally. The broad substrate applicability of Ru/NbOx catalyst for ester production is demonstrated. This process offers a sustainable and efficient approach with high CO utilization and atom economy for the synthesis of esters. Alkoxycarbonylation reactions are widely used in the chemical industry, but their sustainability is often hindered by inefficient CO utilization. Here, the authors tackle the challenge by developing a sustainable and efficient carbonylation process for producing methyl propionate, achieving high CO utilization and regioselectivity. [ABSTRACT FROM AUTHOR]

The main pathway of the reaction of benzal and benzyl halides with phosphorus(iv) acid esters followed the dehalophosphonyl/phosphinyl(oxylation) course and led to the corresponding carbonyl-containing compounds or benzyl esters. A new reaction between α-chloro ethers and O-alkyl diethylphosphinates was discovered. The reactions of benzyl halides with esters of phosphorus(iv) and orthocarboxylic acids were catalyzed by anhydrous zinc chloride. [ABSTRACT FROM AUTHOR]

A new hederagenin-type triterpene saponin was found in the aqueous-ethanolic extract of the seeds of Cassia fistula L. The structure of this compound was established as 3-O-β-D-xylopyranosyl-(1→2)-β-D- xylopyranosylhederagenin 28-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranosyl ester (1), mainly by extensive 2D NMR analysis in combination with spectral data of known compounds. [ABSTRACT FROM AUTHOR]

Mexican Coccoloba uvifera fruit contains polyphenols, flavonoids, and anthocyanins, while in the leaves, lupeol, α- and β-amyrin have been previously identified by HPLC. However, the low resolution by HPLC of pentacyclic triterpenes (PTs) is a limitation. Moreover, the volatile profile of C. uvifera fruit is still unknown. Therefore, this study aimed to identify PTs in C. uvifera leaf and fruit extracts by CG-MS analysis and to determine the volatile profile of C. uvifera pulp by headspace solid-phase microextraction. The results showed trimethylsilylated compounds of standards lupeol, α- and β-amyrin, indicating that the silylation reaction was suitable. These trimethylsilylated compounds were identified in leaf and fruit extracts. The fruit volatile profile revealed the presence of 278 esters, 20 terpenes, 9 aldehydes, 5 alcohols, and 4 ketones. The fruit showed a high content of esters and terpenes. Due to their flavour properties, esters are essential for the food, cosmetics, and pharmaceutics industries. Moreover, terpenes in the fruit, such as menthone, β-elemene, junipene, and β-caryophyllene have the potential as anticancer and phytopathogen agents. The results indicated that GC-MS is an alternative to HPLC approaches for identifying PTs. Besides, identifying volatile compounds in the fruit will increase the value of this plant and expand its application. Identifying PTs and volatile compounds in Mexican C. uvifera leads to a better understanding of the potential benefits of this plant. This would increase the consumption of Mexican C. uvifera fresh or as functional ingredients in nutraceutical or pharmaceutical products. [ABSTRACT FROM AUTHOR]

A facile esterification of α,β-unsaturated aldehydes with alcohols has been developed for the synthesis of esters by using bulky N-heterocyclic (NHC) carbene as a metal-free and eco-friendly organocatalyst. This new protocol has been proved to be effective with a wide substrate scope, giving selective esters in yields greater than 84% under mild conditions. Moreover, proposed synthetic strategy enables modification of various types of silsesquioxanes (SQ) which cannot or are technically difficult to be carried out with known protocols. For the first time, a one-pot sequential esterification/hydrosilylation has been successfully carried out. [ABSTRACT FROM AUTHOR]

Aptamers are oligonucleotides with antibody-like binding function, selected from large combinatorial libraries. In this study, we modified a DNA aptamer library with N-hydroxysuccinimide esters, enabling covalent conjugation with cognate proteins. We selected for the ability to bind to mouse monoclonal antibodies, resulting in the isolation of two distinct covalent binding motifs. The covalent aptamers are specific for the Fc region of mouse monoclonal IgG1 and are cross-reactive with mouse IgG2a and other IgGs. Investigation into the covalent conjugation of the aptamers revealed a dependence on micromolar concentrations of Cu2+ ions which can be explained by residual catalyst remaining after modification of the aptamer library. The aptamers were successfully used as adapters in the formation of antibody-oligonucleotide conjugates (AOCs) for use in detection of HIV protein p24 and super-resolution imaging of actin. This work introduces a new method for the site-specific modification of native monoclonal antibodies and may be useful in applications requiring AOCs or other antibody conjugates. Site-specific conjugation of oligonucleotides and native proteins remains challenging. Here, the authors select covalent DNA aptamers from a library modified with N-hydroxysuccinimide esters, and show their application in the formation of antibody–oligonucleotide conjugates for protein detection. [ABSTRACT FROM AUTHOR]

Determining the content of the nutrient choline in foods and obtaining the required amount from the diet are crucial. One way to measure choline in foods is by converting choline esters to free choline via acid hydrolysis, followed by quantifying the total choline, as adopted by the AOAC method (AOAC-Choline); however, certain choline esters are difficult to hydrolyse. Here, we investigated various acid hydrolysis conditions to establish a reliable method for determining the total choline in foods by detecting free choline using highly sensitive and selective mass spectrometry. Hydrolysis in 0.055 mol/L HCl for 8 h in an autoclave (121 °C) was found to be optimal for the hydrolysis of choline esters in various foods. Twenty-four foods, including grains, seed, vegetables, fruits, mushroom, algae, fish, meats, beverage, processed foods, and egg, were measured. The trends in the total choline content were consistent with previous reports; however, the choline content was 10–20% higher than that measured using AOAC-Choline. Therefore, re-evaluation of the total choline content in foods using our constructed method is recommended. This reassessment will allow for a more reliable determination of choline intake for maintaining health. [ABSTRACT FROM AUTHOR]

The evolution of high-frequency communication has accentuated the significance of controlling dielectric properties in polymer media. Traditionally, it has been theorized that rigid molecular chains lead to lower dielectric loss. However, the validity of this proposition at high frequencies remains uncertain. To scrutinize the correlation between chain flexibility and dielectric properties, we synthesized six poly(ester imide)s (PEIs) with systematically varied molecular chain flexibilities by modifying the ester's substitution on the aromatic ring. The introduction of ester bonds bestowed all PEI films with a low dielectric dissipation factor (Df), ranging from 0.0021 to 0.0038 at 10 GHz in dry conditions. The dry Df displayed a pattern consistent with volume polarizability (P/V). Unexpectedly, PI-mmm-T, featuring the most flexible molecular chain, exhibited the lowest dielectric loss under both dry (0.0021 @ 10 GHz) and hygroscopic (0.0029 @ 10 GHz) conditions. Furthermore, the observed increase in Df after humidity absorption suggests that the high dielectric loss of PEI in applications may be attributed to its hygroscopic nature. Molecular simulations and characterization of the aggregation structure revealed that the smaller cavities within flexible molecular chains, after close stacking, impede the entry of water molecules. Despite sacrificing high-temperature resistance, the precursor exhibited enhanced solubility properties and could be processed into high-quality films. Our research unveils new insights into the relationship between flexibility and high-frequency dielectric loss, offering innovative perspectives on synthesizing aromatic polymers with exceptional dielectric properties. [ABSTRACT FROM AUTHOR]

Benzoxazine dimers are a group of compounds with a variety of properties, such as anticancer properties and good chelating behaviors. The modification of the benzoxazine dimers can be carried out on the OH groups as well as the benzene moiety. There are several works reported on the property adjustment involving the use of different substituent groups on the benzene ring. Only a few works described the properties and crystallographic studies of the OH-modified benzoxazine dimer. The repulsion forces between two bulky benzoyl groups push them to be more distant compared to the unmodified benzoxazine dimer. According to the crystallographic information, the C—H···O, C—H···π, and π···π interactions hold neighbor molecules together, which consequently stabilize the crystal structure. Thermal analyses (TGA and DSC) reveal that the synthesized benzoated benzoxazine dimer is stable up to 175 °C. Hirshfeld surface analysis confirmed the presence of the C—H···O and C—H···π interactions as seen from the high contributions of the following contacts: H···H (60.6%), H···C/C···H (25.1%), and H···O/O···H (12.3%). Moreover, the observed π···π interaction is supported by the shape-index property of the corresponding Hirshfeld surface. For the solid-state photoluminescence of the di-benzoated benzoxazine dimer recorded at the excitation wavelength range from 265 to 320 nm, the emission peak at 490 nm is observed together with another peak or shoulder in the range of 440–480 nm. For all the excitation wavelengths studied, the di-benzoated dimer emits the fluorescence in the blue color shades (CIE coordinate of x at 0.137–0.142 and y at 0.200–0.262). The photoluminescence property is found to originate by the benzoate modification of the benzoxazine dimer. [ABSTRACT FROM AUTHOR]

Esters with pronounced antimicrobial and antifungal activity were synthesized via acylation by benzoyl chloride of the natural hydroxyl-containing compounds 1-octanol, thymol, and 4-bromothymol (thymol benzoate and 4-bromothymol benzoate for the first time). The antimicrobial activity of the synthesized compounds was determined experimentally on three strains of bacteria (Bacillus subtilis 10986 and 4419 and B. licheniformis 537) and the yeast fungus Yarrowia lipolytica W29. Chloramphenicol was chosen as the reference drug for testing the antibacterial activity of the synthesized compounds. Clotrimazole was used as the reference drug in mycostatic tests. Antimicrobial and antifungal tests of the synthesized compounds showed positive results, which opened up possibilities for further research of these compounds as antifungal and antibacterial drugs devoid of the toxicity inherent in benzoic acid. [ABSTRACT FROM AUTHOR]

The present study examines for the first time the emission patterns and olfactory signatures of 9 complete human corpses of different stages of decomposition. Air sampling was performed inside the body bags with solid sorbents and analysed by coupled gas chromatography-mass spectrometry after thermal desorption (TD-GC-MS). Furthermore, odour-related substances were detected by gas chromatography-olfactometry (GC-O). Sulfurous compounds (mainly dimethyl di- and trisulfide) were identified as most important to the odour perception. Around 350 individual organic substances were detected by TD-GC-MS, notably sulfurous and nitrogenous substances as well as branched alkanes, aldehydes, ketones, alcohols, carboxylic acids, carboxylic acid esters and ethers. A range of terpenes was detected for the first time in a characteristic emission pattern over all decomposition stages. Concentrations of the substances varied greatly, and no correlation between the emission patterns, the stage of decomposition and the cause of death could be found. While previous studies often analysed pig cadavers or only parts of human tissue, the present study shows the importance of analysing complete human corpses over a range of decomposition stages. Moreover, it is shown that using body bags as a kind of "emission test chamber" is a very promising approach, also because it is a realistic application considering the usual transport and store of a body before autopsy. [ABSTRACT FROM AUTHOR]

As part of the safety assessment of salicylate esters in cosmetics, we developed a metabolism factor based on in vitro to in vivo extrapolation (IVIVE) to provide a better estimation of the aggregate internal exposure to the common metabolite, salicylic acid. Optimal incubation conditions using human liver S9 were identified before measuring salicylic acid formation from 31 substances. Four control substances, not defined as salicylic esters but which could be mistaken as such due to their nomenclature, did not form salicylic acid. For the remaining substances, higher in vitro intrinsic clearance (CLint, in vitro) values generally correlated with lower LogP values. A "High-Throughput Pharmacokinetic" (HTPK) model was used to extrapolate CLint, in vitro values to human in vivo clearance and half-lives. The latter were used to calculate the percentage of substance metabolised to salicylic acid in 24 h in vivo following human exposure to the ester, i.e. the "metabolism factor". The IVIVE model correctly reproduced the observed elimination rate of 3 substances using in silico or in vitro input parameters. For other substances, in silico only-based predictions generally resulted in lower metabolism factors than when in vitro values for plasma binding and liver S9 CLint, in vitro were used. Therefore, in vitro data input provides the more conservative metabolism factors compared to those derived using on in silico input. In conclusion, these results indicate that not all substances contribute equally (or at all) to the systemic exposure to salicylic acid. Therefore, we propose a realistic metabolism correction factor by which the potential contribution of salicylate esters to the aggregate consumer exposure to salicylic acid from cosmetic use can be estimated. [ABSTRACT FROM AUTHOR]

A new oleanane-type triterpene glycoside, 3-O-α-L-arabinopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyloleanolic acid 28-O-β-D-xylopyranosyl-(1→3)-β-D-xylopyranosyl-(1→2)-β-D-glucopyranosyl ester, was isolated from the aqueous-ethanolic extract of the seeds of Nephelium lappaceum L. The structure elucidation of this compound was based on analyses of spectroscopic data, including 1D and 2D NMR and HR-ESI-MS techniques, and by comparing their NMR data with those reported in the literature. [ABSTRACT FROM AUTHOR]

When treated with cycloalkylamines (pyrrolidine, piperidine, morpholine, and N-methylpiperazine), polyfluoro-containing benzoic and salicylic acid esters undergo chemoselective nucleophilic aromatic substitution of a fluorine atom in the para position to form 4-(N-cycloalkylamino)-substituted derivatives. The hydrolysis of the latter compounds with alkali in aqueous methanol affords the corresponding acids. Methyl 3,5-difluoro-2-hydroxy-4-(piperidin-1-yl)benzoate exhibits high antibacterial activity against the N. gonorrhoeae strain, which is twice higher than that of the drug spectinomycin. N-Cycloalkyl-substituted polyfluorobenzoic acids do not show analgesic activity. The effect of the esters is comparable with the activity of the drug diclofenac. The studied compounds have a lower acute toxicity compared to the reference drug. [ABSTRACT FROM AUTHOR]

Twelve polyoxygenated cyclohex(a/e)ne diterpene esters, named albiflorenes A–L (1–12), were isolated from the whole plants of Kaempferia albiflora, known as "Prao Mang Mum." Their structures and relative stereochemistry were determined by extensive spectroscopic analysis. Furthermore, the comparison of experimental electronic circular dichroism (ECD) curves with the curves predicted by TDDFT was used to determine the absolute configurations. Albiflorenes contain polyoxygenated cyclohexane (or cyclohexene) derivatives, which are linked to either isopimarane or abietane diterpene acid units. The discovery marks the first occurrence of a conjugate between polyoxygenated cyclohexane (or cyclohexene) rings and diterpenoids. Among the isolates, albiflorene C specifically exhibited antibacterial activity against Bacillus cereus with MIC and MBC values of 3.13 and 6.25 μg/mL, respectively. [ABSTRACT FROM AUTHOR]

Esterases are crucial biocatalysts in chiral compound synthesis. Herein, a novel esterase EstSIT01 belonging to family V was identified from Microbacterium chocolatum SIT101 through genome mining and phylogenetic analysis. EstSIT01 demonstrated remarkable efficiency in asymmetrically hydrolyzing meso-dimethyl ester [Dimethyl cis-1,3-Dibenzyl-2-imidazolidine-4,5-dicarboxyate], producing over 99% yield and 99% enantiomeric excess (e.e.) for (4S, 5R)-monomethyl ester, a crucial chiral intermediate during the synthesis of d-biotin. Notably, the recombinant E. coli expressing EstSIT01 exhibited over 40-fold higher activity than that of the wild strain. EstSIT01 displays a preference for short-chain p-NP esters. The optimal temperature and pH were 45 °C and 10.0, with Km and kcat values of 0.147 mmol/L and 5.808 s− 1, respectively. Molecular docking and MD simulations suggest that the high stereoselectivity for meso-diester may attribute to the narrow entrance tunnel and unique binding pocket structure. Collectively, EstSIT01 holds great potential for preparing chiral carboxylic acids and esters. [ABSTRACT FROM AUTHOR]

The method for the preparation of 3,6-disubstituted 1,2,4-triazines based on condensation reaction between easily available α-imino esters and isonitrosoacetophenone hydrazones was reported. The significant differences in reaction conditions, ratio of products, and yields between the developed method and the earlier reported approach were demonstrated. The corresponding 2,5-disubstituted pyridines were synthesized from the prepared 1,2,4-triazines, and their photophysical properties were studied. Studies of the photo-physical properties revealed low and moderate luminescence quantum yields, and negligible solvatochromic behavior in case of 4-methoxyphenylpyridine derivative due to the role of donating methoxy group, however, with a low linearity of a Lippert–Mataga plot. Nevertheless, 2,5-disubstituted pyridines are of interest due to simple protocols of synthesis, moderate photophysical properties, and potential applicability in different scientific and industrial areas. [ABSTRACT FROM AUTHOR]

Convenient methods for the synthesis of a series of organophosphorus analogs of glycine containing aminomethyl groups as well as azaheterocyclic and amino acid moieties have been developed. Aminomethylation of phosphinic acid esters with chloro-, alkoxy- and amino-substituted methyl(dialkyl)amines affords various new functionalized aminomethylphosphonites and bis(aminomethyl)phosphinates. The resulting compounds are of interest as promising biologically active substances, extractants, and water-soluble ligands. [ABSTRACT FROM AUTHOR]

Banana (Musa nana L.) is a typical tropical and climacteric fruit. Post-harvest ripening is an important process involving changes in banana quality. The key physicochemical indicators associated with the quality of bananas were analysed during storage at 12 ℃. The gas compounds released during the storage of banana fruits were measured in situ using solid-phase microextraction tandem gas chromatography–mass spectrometry (SPME–GC–MS). The results showed that the L* value, weight loss, and solid/acid ratio significantly increased during post-ripening, while the a* value, firmness, titratable acidity (TA), and total phenol content showed a marked decrease. Among the released volatiles, esters were the most abundant gases, accounting for approximately 90% of the total gas amount. After analysing the correlation between volatiles and physicochemical parameters, the total volatile and ester contents were found to have a significant positive correlation with the a* value and solid/acid ratio, as well as an obvious negative correlation with the firmness. This study provides a reference for monitoring the ripening state of banana fruit by non-destructive measurement of its released gases in situ. [ABSTRACT FROM AUTHOR]

One of the four cutinases encoded in the Aspergillus nidulans genome, ANCUT1, is described here. Culture conditions were evaluated, and it was found that this enzyme is produced only when cutin is present in the culture medium, unlike the previously described ANCUT2, with which it shares 62% amino acid identity. The differences between them include the fact that ANCUT1 is a smaller enzyme, with experimental molecular weight and pI values of 22 kDa and 6, respectively. It shows maximum activity at pH 9 and 60 °C under assayed conditions and retains more than 60% of activity after incubation for 1 h at 60 °C in a wide range of pH values (6–10) after incubations of 1 or 3 h. It has a higher activity towards medium-chain esters and can modify long-chain length hydroxylated fatty acids constituting cutin. Its substrate specificity properties allow the lipophilization of alkyl coumarates, valuable antioxidants and its thermoalkaline behavior, which competes favorably with other fungal cutinases, suggests it may be useful in many more applications. [ABSTRACT FROM AUTHOR]

Development of energy-efficient lubricants is a way to reduce energy consumption for transportation, with the tendency to design molecules that are beneficial in reducing the viscosity of synthetic oils. Oligoether esters (OEEs), as a low-viscosity ester base oil, have characteristics such as simple synthesis and excellent lubrication effect, however, the application of OEEs in tribology field has rarely been investigated. The objective of the present study is to investigate the effect of structure on the lubricating performance of OEEs and to develop a predictive model for OEEs based on quantitative structure-property relationship (QSPR) through a combination of experiment and statistical modeling. Results showed that glycol chains contribute positively to lubrication with the ether functional groups increasing the sites of adsorption. Compared to branched-chain OEEs, straight-chain OEEs exhibited reduced wear, which was mainly due to the thicker adsorption film formed by the straight-chain structure. Furthermore, carbon films were detected on lightly worn surfaces, indicating that OEEs underwent oxidation during the friction process. Based on the results of principal component analysis (PCA) and partial least squares (PLS), it could be found that the predictive models of viscosity–temperature performance, thermal stability performance, coefficient of friction (COF), and wear volume (WV) performed well and robustly. Among them, COF and WV can be best predicted with an R2 of about 0.90. [ABSTRACT FROM AUTHOR]

R-Oxo hydroformylation processes on rhodium phosphite complexes developed at LLC «RN-RD CENTER» are described – selective production of n-butyral from propylene (R-Oxo I), production of a mixture of n-butyral and isobutyral in equal parts (R-Oxo II), selective production of n-pentanal from a mixture of linear butenes (R-Oxo III). A scheme for the hydroformylation of propylene with membrane separation of the catalyst from the heavy reaction products is described.The analysis of the direction of using C3–C5 oxosynthesis products as raw materials for the production of ester lubricants is carried out. [ABSTRACT FROM AUTHOR]

The instability of asphaltenes in crude oils, manifested in their precipitation, is a major production issue that may arise both during the recovery and processing of petroleum feedstocks. The purpose of this study was to investigate the molecular structure of asphaltenes in order to shed light on the causes of their precipitation. To this end, the molecular structures of stable (remaining in the solution) and unstable (precipitated) asphaltenes were characterized by EPR, NMR, and IR spectroscopy. Using crude oil asphaltenes and air-blown asphalt as objects for the study, only weak increasing and decreasing trends were observed in the content of aromatics and oxygenates, respectively, in the unstable asphaltene fraction. The stable and unstable asphaltenes were found to differ in adsorption capacity. It was shown that the species adsorbed on asphaltenes are rich in moieties of aromatic acid esters, and that removing these species further eliminates the structural-group composition differences between stable and unstable asphaltenes. The study findings suggest that the stability of asphaltenes in crude oils can be controlled by introducing synthetic aromatic acid esters structurally similar to natural surfactants. [ABSTRACT FROM AUTHOR]

In recent years, organophosphate esters (OPEs) have become one of the most common additives in various consumer products worldwide, therefore the exposure and impact of OPEs on human health are drawing a lot of attention. In this study, three metabolites of OPEs including bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), diphenyl phosphate (DPhP) and diethyl phosphate (DEP) were investigated in first-morning void urine samples taken from a population (age range: 3–76 years old) in Hanoi, Vietnam. The most dominant urinary OPE metabolite was DEP with the geometric mean of specific gravity adjust (SG-adjusted) concentration were 1960 ng mL−1 and detected frequency (DF) of 98%. Followed by DPhP (8.01 ng mL−1, DF: 100%) and BDCIPP (2.18 ng mL−1, DF: 51%). The results indicated that gender and age might have associations with the OPE metabolites variation in urine samples. The levels of OPE metabolites in urine samples from females were slightly higher than in males. An increase in age seems to have an association with a decrease in DPhP levels in urine. Exposure doses of parent OPEs were evaluated from the unadjusted urinary concentration of corresponding OPE metabolite. The estimated exposure doses of triethyl phosphate (TEP) (mean: 534,000 ng kg−1 d−1) were significantly higher than its corresponding reference dose, suggesting the high potential risk from the current exposure doses of TEP to human health. The results of this work provided the initial information on the occurrence of three OPE metabolites in urine from Hanoi, Vietnam and estimated exposure dose of corresponding parent OPEs. [ABSTRACT FROM AUTHOR]

Fixed dose combinations (FDCs) incorporating two or three medicines in a single inhaler have been created to enhance patient compliance and hence clinical outcomes. However, the development of dry powder inhalers (DPIs), particularly for FDCs, faces challenges pertinent to formulation uniformity and reproducibility. Therefore, this project aimed to employ nanotechnology to develop a FDC of DPIs for market-leading medicines—fluticasone propionate (FP) and salmeterol xinafoate (SAL)—for asthma management. Nanoaggregates were prepared using a novel biocompatible and biodegradable poly(ester amide) based on the amino acid tyrosine, utilising a one-step interfacial polymerisation process. The produced tyrosine poly (ester amide) drug-loaded nanoparticles were evaluated for content uniformity, PSA, FTIR, TEM, DSC, XRD and aerodynamic performance (in vitro and in vivo). The optimised formulation demonstrated high entrapment efficiency– > 90%. The aerodynamic performance in terms of the emitted dose, fine particle fraction and respirable dose was superior to the carrier-based marketed product. In-vivo studies showed that FP (above the marketed formulation) and SAL reached the lungs of mice in a reproducible manner. These results highlight the superiority of novel FDC FP/SAL nanoparticles prepared via a one-step process, which can be used as a cost-effective and efficient method to alleviate the burden of asthma. [ABSTRACT FROM AUTHOR]

Oleanane-type ginsenosides are a class of compounds with remarkable pharmacological activities. However, the lack of effective preparation methods for specific rare ginsenosides has hindered the exploration of their pharmacological properties. In this study, a novel glycoside hydrolase PlGH3 was cloned from Paenibacillus lactis 154 and heterologous expressed in Escherichia coli. Sequence analysis revealed that PlGH3 consists of 749 amino acids with a molecular weight of 89.5 kDa, exhibiting the characteristic features of the glycoside hydrolase 3 family. The enzymatic characterization results of PlGH3 showed that the optimal reaction pH and temperature was 8 and 50 °C by using p-nitrophenyl-β-d-glucopyranoside as a substrate, respectively. The Km and kcat values towards ginsenoside Ro were 79.59 ± 3.42 µM and 18.52 s−1, respectively. PlGH3 exhibits a highly specific activity on hydrolyzing the 28-O-β-d-glucopyranosyl ester bond of oleanane-type saponins. The mechanism of hydrolysis specificity was then presumably elucidated through molecular docking. Eventually, four kinds of rare oleanane-type ginsenosides (calenduloside E, pseudoginsenoside RP1, zingibroside R1, and tarasaponin VI) were successfully prepared by biotransforming total saponins extracted from Panax japonicus. This study contributes to understanding the mechanism of enzymatic hydrolysis of the GH3 family and provides a practical route for the preparation of rare oleanane-type ginsenosides through biotransformation. Key points: • The glucose at C-28 in oleanane-type saponins can be directionally hydrolyzed. • Mechanisms to interpret PlGH3 substrate specificity by molecular docking. • Case of preparation of low-sugar alternative saponins by directed hydrolysis. [ABSTRACT FROM AUTHOR]

N-Benzenesulfonyl amino acid esters have drawn much attention due to their pharmacological and biological activity. Herein, a facile and effective one-pot approach to N-benzenesulfonyl amino acid esters has been developed, and 16 compounds have been obtained in excellent yields (90–95%) in a short time (9–14 min) using 4-bromobenzenethiol and amino acid esters as starting materials. Significantly, methyl 2-(4-bromoben-zene-sulfon-amido)acetate (3a) could enhance the proline content of soybean in response to excess cadmium in a way similar to the plant hormone abscisic acid. [ABSTRACT FROM AUTHOR]

3-monochloropropane-1,2-diol esters (3-MCPD-Es), 2-monochloropropane-1,3-diol esters (2-MCPD-Es), and glycidyl esters (G-Es) are heat-induced pollutants that formed during the vegetable oil refining process. The current study investigated the effects of heated palm oil containing measured amounts of MCPD-Es and G-Es on rats' lipid profile, liver and kidney functions. Using gas chromatography-mass spectrometry, 3-MCPD-Es, 2-MCPD-Es, and G-Es concentrations in heated palm oil were determined at various intervals. Forty healthy male Sprague–Dawley rats (200–250 g) were divided into four groups (I to IV). Group I was fed a regular diet (negative control). Groups II, III and IV were fed a regular diet fortified with 15% (w/w) of unheated palm oil, palm oil heated at 200 °C for 15 min, and palm oil heated at 200 °C for 30 min, respectively, for 8 weeks. The rats were fed an ordinary diet with nutritional pellets and given water ad libitum. The animal groups were sacrificed, blood samples taken, and the tissues stained with hematoxylin and eosin. The results showed that 3-MCPD-Es, 2-MCPD-Es and G-Es in heated palm oil were 5.4, 3.3 and 2.1 mg kg−1 oil, respectively, and formed at the mildest tested conditions (200 °C, 30 min). Palm oil heated at 200 °C for 30 min increased liver enzymes (alanine transaminase, aspartate transaminase, and alkaline phosphatase), serum kidney functions (uric acid, urea, and creatinine) and lipid profile (plasma cholesterol, plasma triglycerides, LDL-cholesterol, and VLDL-cholesterol) while decreasing HDL-cholesterol compared to rats fed a regular diet. Histological changes occurred in the liver and kidney of rats. It could be concluded that levels of MCPD-Es and G-Es in heated palm oil may pose a potential risk to the health of consumers and need to be constantly monitored. [ABSTRACT FROM AUTHOR]

An efficient reaction between triphenylphosphine or triphenyl phosphite and 2-oxoindoline-3-ylidene derivatives in the presence of acetylenic esters leads to functionalized 2-oxoindoline-3-ylidene containing phosphorus ylieds or phosphonate esters. All compounds obtained in these reactions are stable and have good yields. [ABSTRACT FROM AUTHOR]

Background: Puerarin, a flavonoid abundantly found in the roots of Pueraria lobata, exhibits antioxidant, anti-cancer, anti-inflammatory, and anti-aging properties. Despite its numerous benefits, the low bioavailability of puerarin hinders its widespread industrial application. To improve this, flavonoid acylation is required. Lipase is a biocatalyst primarily used for flavonoid acylation; immobilized lipase is preferred given the limited stability of free lipase. Although research on flavonoid acylation for structural modification is actively being conducted, there is a need to explore continuous production for enhancing the industrial application of flavonoid esters. Therefore, in this study, we aimed to produce puerarin palmitate innovatively by selecting an effective lipase, developing an immobilized lipase, characterizing the enzymatic reaction, and designing a semi-continuous reactor system. Results: Lipase from Thermomyces lanuginosus (TL) was found to be the most suitable for the synthesis of puerarin palmitate; it was successfully immobilized on glutaraldehyde-activated silica gel (GASG). TL GASG showed greater solvent, thermal, and operational stability than those of commercial immobilized lipases. Furthermore, TL GASG use resulted in a puerarin palmitate conversion rate of 97.17% within 3 h. Additionally, the reusability of TL GASG for this reaction was higher than that of commercially available immobilized lipases. Upon using a semi-continuous reactor, the cumulative conversion rate of puerarin palmitate remained above 85% after more than ten substrate injections. Conclusions: The results support the feasibility of the continuous production of flavonoid esters, underscoring their diverse industrial applications. A biorefinery strategy is anticipated to be proposed to utilize P. lobata extract biomass for flavonoid ester production. Moreover, optimizing continuous reactors through statistical experimental design is expected to enhance flavonoid ester production efficiency; these aspects will be explored in future research. Highlights: The stability of TL GASG was higher than commercial immobilized lipases. The novel immobilized lipase was applied to puerarin ester synthesis. The maximum conversion of puerine palmitate was achieved 97.17% in 3 h. Conversion rate via semi‐continuous reaction was maintained > 85% after 10 injections. [ABSTRACT FROM AUTHOR]

Continuous flow chemistry has become the method of choice for the synthesis of toxic and explosive intermediates such as diazo reagents because they can be generated on demand and readily used, eliminating the need to handle hazardous materials. This inherent increase in safety makes it more feasible to use these reagents in day-to-day synthesis. Herein, we describe a continuous flow, metal-free, easy-to-use method for the preparation of semi-stabilized and unstabilized diazo reagents. The scope of the described continuous flow oxidation of hydrazones using a packed bed column with iodosylbenzene includes 13 semi-stabilized and 13 unstabilized diazo reagents in solution in dichloromethane while producing only 1 equivalent of water and iodobenzene as by-products. These otherwise difficult to access compounds are further reacted either in situ or at the reactor outlet to yield esters and ethers in good to excellent yields (47–96%). [ABSTRACT FROM AUTHOR]

The mechanism of enamine-mediated organocatalytic [3 + 2] cycloaddition (32CA) reaction of Hagemann's ester to p-toluenesulfonyl azide in the present L-proline as a catalyst has been investigated using M06-2X functional with the 6-31+G(d) basis set. The effects of the different solvents were studied with a 6-311+G(d,p) basis set. In addition, the effects of the keto ester substitutions: one model system M1 (R1 = CH3 and R2 = H) and two real systems R2 (R1 = R2 = Me) and R3 (R1 = Et and R2 = Me) also studied in this work. DFT results indicated that the different solvents show the same effect, which leads to a decrease in the ΔG298 along the reaction pathway compared to the gas phase. Moreover, the model system M1 has a lower activation free energy (17.5 kcal/mol) than real systems R2 and R3 by about 3.8 and 3.2 kcal/mol in the solution phase (DMSO), respectively. Analysis of the global and local reactivity indices of the reactants was performed in the gas and solution phases. [ABSTRACT FROM AUTHOR]

The remarkable development in high-voltage direct current and high-voltage alternating current transmission systems calls for a renewed assessment of dielectric liquids for insulation systems of transformers. The function of liquid insulation used in high-voltage equipment is cooling and insulation. It should have several features like high dielectric strength, low viscosity, high flash point, very low moisture or water content, high specific resistance and many more. Petroleum-dependent synthetic and mineral oil has been conventionally applied as dielectric fluids in transformers during previous some decades that disturbs the environment on account of their low biodegradability and low fire point which have persuaded the exploration of substitutes. The application of alternate insulating fluids is increasing gradually, with safety and environmental apprehensions at the lead of the grounds for shifting from mineral oil. Esters-based dielectric fluids have been used in dielectric industry for roughly four decades, with synthetic esters having initially been proposed to replace harmful polychlorinated biphenyls or PCBs in late 1970s. Ester-based liquids found applications in distribution transformers without any significant design modifications in standard mineral oil designs, although could not be applied at high-voltage levels. From this finding, dielectric society and manufacturers have boarded on a search for an evident insight of the elementary differences between esters and mineral oil and how to adapt designs to allow the application of esters at high-voltage levels. Synthetic and natural esters have been exposed to research for years vis-a'-vis mineral oil around the globe. Even though several investigators are in favor of ester liquids use in high-voltage equipment, manufacturers and utilities are yet averse, and use of these alternative fluids stays a challenge. This paper will present an analysis of the published research results during the past few decades from various researchers, emphasizing the variations in dielectric performance between esters and mineral oil. This knowledge transfer is timely as it presents challenges and prospective attributes that would be considered further to enhance the accessible information of ester dielectric fluids for application in transformers. [ABSTRACT FROM AUTHOR]

Gastric ulcer is one of the most frequent gastrointestinal ailments worldwide. Indomethacin, one of the most potent NSAIDs, suffers undesirable ulcerogenic activity. Caffeic acid phenethyl ester (CAPE) has known health benefits. The current study examined the potential of CAPE to combat indomethacin-induced gastric ulcers in rats. Animals were randomized into 5 groups: control, Indomethacin (50 mg/kg) mg/kg), Indomethacin + CAPE (5 mg/kg/day), Indomethacin + CAPE (10 mg/kg), and Indomethacin + Omeprazole (30 mg/kg). CAPE prevented the rise in ulcer index, attenuated histopathological changes and preserved gastric mucin concentration. CAPE efficiently significantly prevented accumulation of malondialdehude (MDA) and prevented exhaustion of the enzymatic activities of catalase (CAT) and superoxide dismutase (SOD). Further, CAPE prevented the rise in the expression of tumor necrosis factor-α (TNF-α), cyclo-oxygenase-2 (COX-2) and nuclear factor kapp-B (NFκB). This was associated with down-regulation of Bax and up-regulation of Bcl-2 mRNA. Finally, CAPE prevented induced indomethacin-induced decrease in heat shock protein 70 (HSP70) in gastric tissues. In conclusion, CAPE possesses the ability to prevent indomethacin-induced gastric ulcer in rats. This involves, at least partially, antioxidation, anti-inflammation, anti-apoptosis and enhancement of HSP70 expression. [ABSTRACT FROM AUTHOR]

Developing bio-based hyperbranched ester plasticizers using woody oil by a simple strategy to replace toxic phthalate plasticizers has significant social, environmental, and economic significance. Herein, a series of tung oil-based hyperbranched esters (TPPs) were synthesis through a one-pot method, the degree of branching and relative molecular weight of the TPPs were controlled by adjusting the glycidyl content. The TPPs were used to plasticize polyvinyl chloride (PVC) materials. The results indicated that TPPs showed better plasticizing properties, transmittance and migration stability compared with commercial dioctyl phthalate (DOP). For instance, the tensile strain of PVC/TPP-9 reached to 560%, and transmittance was 42.1%. In addition, the PVC/TPPs films possessed excellent shape memory performance, and shape fixity and shape recovery were up to 97 and 91%, respectively. The cohesive energy was simulated and calculated from the perspective of energy to first predict the ability of plasticizers migrated from the PVC matrix. These hyperbranched ester plasticizers exhibited the potential to substitute DOP in the fields with strict requirements (e.g. food packaging, toys for children). [ABSTRACT FROM AUTHOR]

The production of catalytic materials from large-scale wastes represents an interesting way of sustainability which is largely untapped resource. The 'waste into treasure' turning strategy provides a possible way for synthesis of nanomaterial, having diverse environmental and industrial applications, in an eco-friendly way. Egg shell is abundantly available, cost-effective and renewable, possessing unique hierarchically porous structure which has been widely investigated in the field of adsorption, energy as well as catalysis. Herein, we are reporting a rationally fabricated LaCoO3 supported egg shell (LaCoO3/ES, LCES) using waste egg shell as template. The synthesized material was characterized using different techniques and used as nanocatalyst. The LaCoO3/ES catalyzed the reduction of 4-nitophenol (4-NP) to less toxic 4-aminophenol (4-AP) and methyl orange into its reduced less hazardous and decolorized product with high efficiency. Amides were also synthesized using base and solvent-free conditions via grinding showing increased catalytic performance. Therefore, the results obtained support a synergistic effect between cobalt and lanthanum ions that enhanced the catalytic activity for both reduction and amidation of esters. In the amidation series, a new product, namely N1, N3-bis(4-methylbenzyl) malonamide, was also synthesized. In addition, we were also able to successfully grow a single crystal of one of the compounds such as N-benzyl-2-cyanoacetamide and confirmed by Single Crystal X-ray Crystallography. [ABSTRACT FROM AUTHOR]

Hazardous properties of a large number of esters of 4-hydroxybenzoic acid (parabens) have been proposed by ECHA to be assessed as a group. We recommend to restrict the grouping approach to short chain esters, i.e. methyl, ethyl, propyl and butyl paraben which are very similar in chemical structures, physicochemical properties, toxicokinetics, and hazardous properties. While these parabens show a weak estrogenicity in some in vitro or in vivo screening assays, they do not induce estrogen-receptor-mediated adverse effects in intact animals. Therefore, there is no support regarding classification and labeling of endocrine disruption or reproductive toxicity of these parabens. [ABSTRACT FROM AUTHOR]

The reaction of 4-amino-substituted 6-hydrazinyl-1,3,5-triazin-2(1H)-ones with triethyl orthoacetate proceeded as a cascade reaction. The initially formed 7-amino-substituted 3-methyl[1,2,4]triazolo[4,3-a][1,3,5]triazin-5(1H)-ones underwent a Dimroth-type rearrangement with the formation of 5-amino-substituted 2-methyl[1,2,4]triazolo[1,5-a][1,3,5]triazin-7(3H)-ones. The latter underwent alkylation at three positions: at the exocyclic oxygen atom with the formation of 7-ethoxy-2-methyl[1,2,4]triazolo[1,5-a][1,3,5]triazines, at the N-3 nitrogen atom with the formation of 3-ethyl-2-methyl[1,2,4]triazolo[1,5-a][1,3,5]triazin-7(3H)-ones, and at the N-1 nitrogen atom to form 1-ethyl-2-methyl[1,2,4]triazolo[1,5-a][1,3,5]triazin-7(3H)-ones. For the latter compound, a retro-Dimroth-type rearrangement occurred with the formation of betaine-type 7-amino-substituted 2-ethyl-3-methyl[1,2,4]triazolo[4,3-a][1,3,5]triazin- 2-ium-5-olates. A possible mechanism for the alkylation of 5-amino-substituted 2-methyl[1,2,4]triazolo[1,5-a][1,3,5]triazin-7(3H)-ones with ortho esters was proposed. [ABSTRACT FROM AUTHOR]

While glycoside hydrolase family 1 (GH1) enzymes mostly catalyze hydrolysis reactions, rice Os9BGlu31 preferentially catalyzes transglycosylation to transfer a glucosyl moiety to another aglycone moiety to form a new glycosylated compound through a retaining mechanism. In this study, Os9BGlu31 was used to synthesize eight phenolic acid glucosyl esters, which were evaluated for activities in cholangiocarcinoma cells. The transglycosylation products of Os9BGlu31 wild type and its mutant variants were detected, produced on a milligram scale, and purified, and their structures were characterized by NMR spectroscopy. The transglycosylation products were evaluated by antioxidant and anti-proliferative assays, followed by an anti-migration assay for the selected phenolic acid glucosyl ester. Os9BGlu31 mutants produced higher yield and activity than wild-type enzymes on phenolic acids to produce phenolic acid glucosyl esters. Among these, gallic acid glucosyl ester (β-glucogallin) had the highest antioxidant activity and anti-proliferative activity in cholangiocarcinoma cells. It also inhibited the migration of cholangiocarcinoma cells. Our study demonstrated that rice Os9BGlu31 transglucosidase is a promising enzyme for glycosylation of bioactive compounds in one-step reactions and provides evidence that β-glucogallin inhibits cell proliferation and migration of cholangiocarcinoma cells. Key points: • Os9BGlu31 transglucosidases produced phenolic acid glucosyl esters for bioactivity testing. • Phenolic acid glucosyl esters were tested for cytotoxicity in cholangiocarcinoma cells. • β-Glucogallin displayed the highest inhibition of cholangiocarcinoma cell growth. [ABSTRACT FROM AUTHOR]

Cyanine dyes are widely used in various techniques of bioimaging. The development of new types of optical tags with cyanine dyes combined with plasmonic nanoparticles is of great interest. In this work, surface-enhanced Raman scattering (SERS) study of optical behavior of cyanines adsorbed on gold nanoparticles in suspensions is presented to predict the optical response of corresponding tags. Two dyes, sulfo-cyanine 5.5 NHS ester and sulfo-cyanine 7.5 NHS ester were considered as they are suitable for the first transparency window of biological tissues. Gold nanoparticles of anisotropic shape were used as a plasmonic substrate. The assignment of bands in SERS spectra of both dyes was performed based on DFT calculations of vibrational frequencies of the molecules. The adsorption of dyes on the nanoparticles with different surface charges was studied. Spectral changes showed that a reorientation of the molecules occurs and reactive NHS ester tail is more accessible sterically in the case of a positive surface charge. The effect of aggregation-induced agent on the SERS response of sulfo-cyanines was also studied. Addition of chloride anions led to about five-fold increase of SERS intensity for sulfo-cyanine 5.5 NHS ester. [ABSTRACT FROM AUTHOR]

Stable water-oil emulsions are formed due to the strong armor layer at the oil/water interface able to prevent the coalescence of water droplets in oil. The stability of water-oil emulsions obtained by mixing solutions of asphaltene in toluene and in heptol (a mixture of n-heptanol and toluene) with distilled water was found to be a function of two asphaltene fractions, namely, a fraction soluble in heptol enriched with ester fragments and a fraction tending to form aggregates in heptol. The surfactant properties of the first fraction permit the formation of a thin shell with low mechanical strength at the oil/water interface. The asphaltene aggregates adsorbed onto this thin shell are compacted over time, imparting rigidity and mechanical strength to the oil/water interface layer. [ABSTRACT FROM AUTHOR]

With the widespread use of organophosphate esters (OPEs), the accumulation and toxicity effect of OPEs in biota are attracting more and more concern. In order to clarify the mechanism of toxicity of OPEs to organisms, this study reviewed the OPEs toxicity and systematically identified the mechanism of OPEs toxicity under the framework of adverse outcome pathway (AOP). OPEs were divided into three groups (alkyl-OPEs, aryl-OPEs, and halogenated-OPEs) and biota was divided into aquatic organism and mammals. The results showed that tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) and triphenyl phosphate (TPHP) mainly caused neurotoxicity, reproductive, and hepatotoxicity in different mechanisms. According to the constructed AOP network, the toxicity mechanism of OPEs on aquatic organisms and mammals is different, which is mainly attributed to the different biological metabolic systems of aquatic organisms and mammals. Interestingly, our results indicate that the toxicity effect of the three kinds of OPEs on aquatic organisms is different, while there was no obvious difference in the mechanism of toxicity of OPEs on mammals. This study provides a theoretical basis for OPEs risk assessment in the future. [ABSTRACT FROM AUTHOR]

The hydro-alcoholic extract of Glycine max (soybean), upon chemical constituents investigation lead to the isolation compound (1) named as soyasaponin A1 ester apart from other known compounds soyasaponins M1, M2, M3, soyasaponin A1, A2, and robinioside. All compounds were characterized by spectroscopic techniques including 2D NMR spectroscopy. [ABSTRACT FROM AUTHOR]

Low-temperature oxidation in air of domestic poly-p-aramid complex threads based on poly(p-phenylene terephthalamide), i.e., terlon, Rusar, and Rusar NT, that were nitrated beforehand by nitrogen dioxide was studied comprehensively by EPR and IR spectroscopy, thermoanalytical methods (TA, TMA), and scanning electron microscopy (SEM). Mechanisms of nitration and destruction of poly-p-aramid complex threads were proposed. The nitrosyl nitrate form of nitrogen dioxide was proposed as the oxidation initiator. The polymers were destroyed by degradation of N-nitrosoamides, N-nitrocompounds, and N- nitrites, i.e., nitration products of terlon, the main component of the thread. IR spectroscopy found that the major products of aramid thread nitration were esters and carboxylic acids. [ABSTRACT FROM AUTHOR]

A method has been optimized for simultaneous extraction of ethyl methylphosphonic acid ester (EMPA), isopropyl methylphosphonic acid ester (IPMPA), isobutyl methylphosphonic acid ester (IBMPA), pinacolyl methylphosphonic acid ester (PMPA), and methylphosphonic acid (MPA), which are highly polar products of nerve agent hydrolysis, from soil with their further determination by high-performance liquid chromatography–high-resolution tandem mass spectrometry (HPLC–HRMS/MS). The ions observed in the fragmentation mass spectra of deprotonated EMPA, IPMPA, IBMPA, PMPA, and MPA molecules and their deuterated analogs (d3-EMPA, d3-IPMPA, d3-IBMPA, d3-PMPA, and d3-MPA), as well as possible structural formulas of the fragment ions, are presented. Liquid extraction with deionized water followed by concentration by evaporation was used to prepare soil samples for analysis. The components were separated using reverse-phase chromatography. The time required for the sample preparation and analysis of the soil samples was no more than 1 h. The detection limits in soil were 0.05 ng/g for EMPA and IPMPA, 0.02 ng/g for IBMPA and PMPA, and 1 ng/g for MPA. [ABSTRACT FROM AUTHOR]