Aromatic Esters Research Articles

Enhancing flavour with non‐Saccharomyces during vinegar alcoholisation: a mechanism study

SummaryThe effects of mixed fermentation of non‐Saccharomyces (Pichia fabianii, Kluyveromyces thermotolerans, and Saccharomycopsis fibuligera) with Saccharomyces cerevisiae on the physicochemical indexes and flavour of rice vinegar fermentation were studied. The mixed fermentation increased the activity of β‐glucosidase and esterification enzyme. The β‐glucosidase activity of P. fabianii was 1.6 times higher than that of S. cerevisiae alone, and the esterification enzyme activity was increased by about four times. Compared with the single fermentation of S. cerevisiae, the mixed fermentation of P. fabianii and S. cerevisiae increased the type and content of aromatic esters and produced ethyl acetate and phenethyl acetate. The mixed fermentation of K. thermotolerans and S. cerevisiae made an outstanding contribution to produce higher alcohols. Among them, the content of isobutanol and phenylethanol increased by nearly ten times; the content of isoamylol increased by more than eight times. S. fibuligera provides a unique flavour of phenols because of 2‐methoxy‐4‐ethylphenol and 2‐methoxy‐4‐ethylphenol.

Impact of seed-roasting treatment on polycyclic aromatic hydrocarbons, 3-MCPD esters, heterocyclic amines and volatile components formation in sunflower oil

Seed-roasting is a crucial process conducted to improve the organoleptic and conservative features of oilseeds. In this paper, raw sunflower seeds were roasted at 160, 180 and 200 °C for various times. Three hazards (polycyclic aromatic hydrocarbons, 3-monochloro-1,2-propanediol esters and heterocyclic amines) and volatile components in the corresponding oil extracted from roasted sunflower seeds were analyzed. Polycyclic aromatic hydrocarbons, 3-monochloro-1,2-propanediol esters and heterocyclic amines were measured using HPLC, GC-MS and UPLC-MS, respectively. Volatiles were determined by GC-MS. The results show that the strength of seed-roasting promoted the formation of the three hazard factors. The contents of polycyclic aromatic hydrocarbons, 3-monochloro-1,2-propanediol esters and heterocyclic amines in sunflower oil increased 9.4, 22.1 and 121.6 fold respectively after roasting at 200 °C for 25 min. The main volatiles were aldehydes and terpenes with a greenish and earthy taste. Volatile levels possessing pleasant flavors of floral, roasted and nuts, particularly aldehydes and pyrazines, generally increased with roasting. However, at high intensity roasting, the appearance of furans would bring burnt, bitter, as well as viscosity, resulting in poor sensory for oil. Considering the limitation of the above mentioned hazards established by EU, the optimal roasting condition of sunflower seed was 180–200 °C for 15–20 min.

Bis(N-Heterocyclic Carbene) Manganese(I) Complexes: Efficient and Simple Hydrogenation Catalysts.

The use of bis(NHC) manganese(I) complexes 3 as catalysts for the hydrogenation of esters was investigated. For that purpose, a series of complexes has been synthesized via an improved two step procedure utilizing bis(NHC)-BEt3 adducts. By applying complexes 3 with KHBEt3 as additive, various aromatic and aliphatic esters were hydrogenated successfully at mild temperatures and low catalyst loadings, highlighting the efficiency of the novel catalytic system. The versatility of the developed catalytic system was further demonstrated by the hydrogenation of other substrate classes like ketones, nitriles, N-heteroarenes and alkenes. Mechanistic experiments and DFT calculations indicate an inner sphere mechanism with the loss of one CO ligand and reveal the role of BEt3 as cocatalyst.

Heterogeneity of microbiome and flavor profiles of industrial-scale Laotan Suancai: Fermentation craft plays important roles

Laotan Suancai is a well-known Chinese traditional fermented vegetable with a unique flavor. However, there are significant differences in the quality of Laotan Suancai pickled by jars (LTSC-J) and pools (LTSC-P) on an industrial scale. To reveal the effect of fermentation craft on Laotan Suancai quality, the microbial community, flavor metabolites, and physicochemical properties of the two types of Laotan Suancai, as well as their interrelationship were investigated. LTSC-P had higher salinity, glucose content, and histidine content, while LTSC-J had higher TA, lactic acid content, and isobutyric acid content. Nine differential aroma-active compounds were found between the two types of Laotan Suancai: anethole, eucalyptol, diallyl sulfide, estragole, diallyl disulfide, eugenol, linalool, nonanal, and ethyl butyrate. LTSC-P showed a higher relative abundance of Weissella, Acinetobacter, Pseudomonas, Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, Inhella, and Leuconostoc compared to LTSC-J. Co-occurrence analysis indicated the distinct differences in the co-occurrence patterns of the microbial network across the two types of Laotan Suancai. RDA analysis indicated that glucose, salinity, TA, maltose, and nitrite were the main drivers for the differences in bacterial communities between the two types of Laotan Suancai. Spearman correlation analysis revealed strong correlations between 18 bacteria and 61 flavor compounds. Finally, bacterial metabolic function prediction indicated that sulfide and aromatic ester may be biosynthesized by sulfur metabolism, cysteine and methionine metabolism, pyruvate metabolism, and butanoate metabolism. Overall, these findings provide important guidance for improving the manufacturing and quality of Laotan Suancai.

Bis(N‐Heterocyclic Carbene) Manganese(I) Complexes: Efficient and Simple Hydrogenation Catalysts

AbstractThe use of bis(NHC) manganese(I) complexes 3 as catalysts for the hydrogenation of esters was investigated. For that purpose, a series of complexes has been synthesized via an improved two step procedure utilizing bis(NHC)‐BEt3 adducts. By applying complexes 3 with KHBEt3 as additive, various aromatic and aliphatic esters were hydrogenated successfully at mild temperatures and low catalyst loadings, highlighting the efficiency of the novel catalytic system. The versatility of the developed catalytic system was further demonstrated by the hydrogenation of other substrate classes like ketones, nitriles, N‐heteroarenes and alkenes. Mechanistic experiments and DFT calculations indicate an inner sphere mechanism with the loss of one CO ligand and reveal the role of BEt3 as cocatalyst.

Effect of Lactobacillus plantarum fermentation on the physicochemical properties and flavor of rice protein-carboxymethylcellulose complexes.

Fermentation is known to enhance the nutritional profile and confer unique flavors to products. However, the resultant effects on stability and physicochemical properties remain unexplored. This study aims to elucidate the influence of fermentation on the stability and organoleptic characteristics of a rice protein beverage stabilized by carboxymethyl cellulose (CMC). The findings revealed that the average aggregate size escalated from 507 to 870 nm, concurrently exhibiting a significant increase in surface potential. The aggregation enhancement was substantiated by evident morphological changes and confocal laser scanning microscopical (CLSM) observations. A negative correlation was discerned between the physical stability of the beverage and fermentation duration. Moreover, flavor analysis of the beverage post a 3 h fermentation period highlighted an increase in aromatic ester compounds, thereby intensifying the aroma. The study corroborates that fermentation can detrimentally influence product stability while concurrently improving its flavor profile. By establishing a mix ratio of 10:1 for rice protein and CMC and forming a relatively stable system through electrostatic interaction at a pH of 5.4, a flavorful rice protein beverage can be derived post 3 h-fermentation process. These findings offer insights into the impact of varying fermentation durations on the stability and flavor of polysaccharide-based rice protein beverages. © 2023 Society of Chemical Industry.

Design of semisynthetic derivatives of the Amaryllidaceae alkaloid ambelline and exploration of their in vitro cytotoxic activities

Ambelline, an alkaloid from the Amaryllidaceae family with a crinane-type skeleton, has not yet demonstrated any outstanding biological activity. However, its analogues prepared by derivatization of the C-11 hydroxyl group show different interesting effects. Continuing our earlier work, twelve novel aromatic esters were developed (10, 14, 16, 17, 22–25, 30–33) and studied, together with previously synthesized derivatives (2–9, 11–13, 15, 18–21, 26–29) in terms of their cytotoxic activity. The cytotoxic potential was determined on a panel of nine human cancer cell lines and one noncancerous cell line to characterize their biological activity spectrum. To describe and foresee the structure–activity relationship for further research, substances synthesized and described in our previous work were also included in this cytotoxicity study. The most significant activity was associated with analogues havingmethyl (10), methoxy (14–17), or ethoxy (18) substitution on the phenyl condensed to ambelline. However, the 4-chloro-3-nitrobenzoyl derivative (32) showed the most promising IC50 values, ranging from 0.6 ± 0.1 µM to 9.9 ± 0.2 µM. In vitro cytotoxicity studies indicated the most potent antiproliferative activity of 32 in a dose-dependent and time-dependent manner. Besides, 32 was found to be effective in decreasing viability and triggering apoptosis of MOLT-4 T-lymphoblastic leukemia cells.

Pilot-scale flue gas pyrolysis system for organic and plastic wastes with improved liquid properties in a non-thermal plasma reactor

A fast, oxidative pyrolysis system was developed to produce a pyrolysis liquid (PyOL) upgraded with a non-thermal plasma (NTP) reactor. In addition to the 1.8 million tonnes per annum of plastic wastes, large amounts of municipal solid waste in Malaysia end up in landfills, of which 40–60 % is organic or food waste. Organic and plastic wastes (OPW) can be used as carbon feedstocks for the pyrolysis process to produce PyOL, reducing the OPW disposal in landfills, and carbon emissions. However, the current pyrolysis methods use pure nitrogen, implying increased operational cost, and are commonly performed at the lab scale. In this study, flue gas was used for the pyrolysis of OPW at a pilot scale. The use of flue gas for PyOL production reduces the operational costs and lifecycle carbon emissions. Results show that the addition of a small percentage of plastics at the pyrolysis temperature of 350 °C increased the yield of liquid. However, large amounts of plastics resulted in significant material agglomeration. A disadvantage of PyOL is the degradation of properties with respect to storage time. Therefore, a NTP reactor was developed to improve the PyOL properties. After NTP treatment, the aromatic and carbonyl ester groups decrease, the calorific value increased, and certain chemical compounds increased in concentration. This study provides operational parameters for the pilot scale pyrolysis (and waste-to-energy) process, improving the technical viability of scaling-up such systems.

Oil Inclusions Found in Skeleton Crystals of Quartz Indicated the Existence of Organic Matter Surrounding Ancient Growth Environments.

In nature, minerals record various origins and information for geology and geobiochemistry. Here, we investigated the origin of organic matter and growth mechanism of quartz with oil inclusion revealing fluorescence under short ultraviolet (UV) light, obtained from the clay vein at Shimanto-cho, Kochi, Shikoku Island, Japan. Geological investigation indicated that the oil-quartz was formed in hydrothermal metamorphic veins found in the late Cretaceous interbedded sandstone and mudstone. The obtained oil-quartz crystals are mostly double-terminated. Micro-X-ray computed tomography (microCT) indicated that oil-quartz crystals have various veins originating as skeleton structures along the quartz crystal {111} and {1-11} faces. Spectroscopic and chromatographic studies indicated that aromatic ester and tetraterpene (lycopene) molecules, which revealed fluorescence, were detected. Large molecular weight sterol molecules, such as C40, were also detected in the vein of oil-quartz. This investigation indicated that organic inclusions in mineral crystals would form with ancient microorganism culture environments.

Synthesis of Anilides by Aminolysis of Unactivated Esters using MnCl2 in Combination with strong Bases as Catalyst

AbstractAnilides are often found in pharmaceuticals and active ingredients in crop protection. Although of great interest, the atom‐ and step economic formation of the amide bond between a less nucleophilic aniline with an acid or ester remains still a major challenge. Herein, we report an aminolysis of aromatic and alkyl esters with anilines catalyzed by a readily available catalytic system comprising of an earth‐abundant Mn‐salt in combination with an inexpensive base.

Synthesis and characterisation of novel aromatic ester swallow-tailed cholesteric liquid crystal polymers

ABSTRACT In this paper, two novel aromatic ester swallow-tailed liquid crystal monomers M1 and M2 and a straight chain cholesteric liquid crystal monomer M3 were designed and synthesised. Two series of liquid crystal polymers, P1 series and P2 series, were graft-copolymerised with M and polymethylhydrosiloxane (PHMS). All the synthesised liquid crystal monomers and polymers were characterised by IR and 1H NMR and confirmed to the predicted molecular structure. The liquid crystal and thermal properties of the synthesised compounds were tested by DSC, POM, TGA and optical rotation. The results show that the monomer M1 is a monotropic nematic liquid crystal, and the Schlieren texture appears during the cooling process. M2 is an enantiotropic nematic liquid crystal with filamentous and schlieren texture. M3 is a thermotropic enantiotropic cholesteric phase with oily streak and focal cone texture. Both polymers P1 and P2 show typical Grand-Jean texture, and with the increase of monomer M3 content, the polymer clearing point temperature Ti increases continuously, the liquid crystal mesophase range widens, and the specific rotation value increases.

Hydrophobic Modification of Poly(γ-glutamic acid) by Grafting 4-Phenyl-butyl Side Groups for the Encapsulation and Release of Doxorubicin.

The delivery of drugs is a great challenge, since most of active pharmaceutical ingredients developed today are hydrophobic and poorly water soluble. From this perspective, drug encapsulation on biodegradable and biocompatible polymers can surpass this problem. Poly(γ-glutamic acid) (PGGA), a bioedible and biocompatible polymer has been chosen for this purpose. Carboxylic side groups of PGGA have been partially esterified with 4-phenyl-butyl bromide, producing a series of aliphatic-aromatic ester derivatives with different hydrophilic-lipophilic balances. Using nanoprecipitation or emulsion/evaporation methods, these copolymers were self-assembled in a water solution, forming nanoparticles with average diameters between 89 and 374 nm and zeta potential values between -13.1 and -49.5 mV. The hydrophobic core containing 4-phenyl-butyl side groups was used for the encapsulation of an anticancer drug, such as Doxorubicin (DOX). The highest encapsulation efficiency was reached for a copolymer derived from PGGA, with a 46 mol% degree of esterification. Drug release studies carried out for 5 days at different pHs (4.2 and 7.4) indicated that DOX was released faster at pH 4.2, revealing the potential of these nanoparticles as chemotherapy agents.

Synthesis and Investigation of Anti-Inflammatory Activity of New Thiourea Derivatives of Naproxen.

The aim of the study was a synthesis and investigation of the dose-dependent anti-inflammatory effect of new thiourea derivatives of naproxen with selected aromatic amines and esters of aromatic amino acids. The results of the in vivo study indicate that derivatives of m-anisidine (4) and N-methyl tryptophan methyl ester (7) showed the most potent anti-inflammatory activity four hours after injection of carrageenan, with the percentage of inhibition of 54.01% and 54.12%, respectively. In vitro assays of COX-2 inhibition demonstrated that none of the tested compounds achieved 50% inhibition at concentrations lower than 100 µM. On the other hand, the aromatic amine derivatives (1-5) accomplished significant inhibition of 5-LOX, and the lowest IC50 value was observed for compound 4 (0.30 μM). High anti-edematous activity of compound 4 in the rat paw edema model, together with potent inhibition of 5-LOX, highlight this compound as a promising anti-inflammatory agent.

Hydrolases in GtoPdb v.2023.1

Listed in this section are hydrolases not accumulated in other parts of the Concise Guide, such as monoacylglycerol lipase and acetylcholinesterase. Pancreatic lipase is the predominant mechanism of fat digestion in the alimentary system; its inhibition is associated with decreased fat absorption. CES1 is present at lower levels in the gut than CES2 (P23141), but predominates in the liver, where it is responsible for the hydrolysis of many aliphatic, aromatic and steroid esters. Hormone-sensitive lipase is also a relatively non-selective esterase associated with steroid ester hydrolysis and triglyceride metabolism, particularly in adipose tissue. Endothelial lipase is secreted from endothelial cells and regulates circulating cholesterol in high density lipoproteins.

Bacterial microbiota and metabolic characteristics of traditional Zhangjiajie Jiuqu aromatic ester vinegar in China

Aged vinegars are popular acidic condiments worldwide, used for their flavour and nutritional value; they also have a rich microbial diversity. This study combined the ultra-performance liquid chromatography-quadrupole-time of flight mass spectrometry (UPLC-Q-TOF-MS) technology with Pacific Biosciences (PacBio) single-molecule real-time (SMRT) sequencing to analyze the microbial population and associated metabolism in six traditional Zhangjiajie Jiuqu aromatic ester vinegars (JAEVs) in China. A total of 265 species and subspecies from 170 bacterial genera and 14 phyla were identified; among these Lactococcus lactis (18.23%) and Acinetobacter johnsonii (17.18%) were the predominant species. A total of 1352 metabolites were detected in the metabolomes of all samples. In addition, occurrence of 40 metabolites detected were significantly different among six samples. Based on correlation analyses between the prevalent bacterial species and main differentially recorded metabolites, we conclude that there were significant correlations (P < 0.05) between 20 metabolites and five bacterial species. Limosilactobacillus fermentum and Hyphomicrobium zavarzinii were the main regulatory strains caused differential metabolites. Some potential functional metabolites were also identified, mainly chlorogenic acid and trans-piceid. This study revealed the relationship between the unique flavour of JAEVs and the microbial community, and provided a basis for industrial production of traditional aged vinegar.

Design, Synthesis, and Applications of a Vanadium Complex: An Effective Catalyst for the Direct Conversion of Alcohols and Aldehydes to Esters.

A novel bench-stable V-catalyst [(L2)VIVO](ClO4) was synthesized and characterized by X-ray diffraction (XRD) analysis and FT-IR, UV-visible, and EPR spectroscopies, which confirmed its excellent catalytic activity. In application, aldehydes are rapidly converted into their corresponding esters without additives in a one-pot manner using a newly developed catalyst [(L2)VIVO](ClO4) and H2O2 as a green oxidant. The developed method is compatible with a broad range of densely substituted aldehydes and allows for the facile preparation of aliphatic, aromatic, and heterocyclic esters, including esters derived from CD3OD, methanol, ethanol, iso-propanol, n-butanol, sec-butyl alcohol, and propargylic alcohol. Gratifyingly, numerous alcohols also directly converted to their corresponding esters in a one-pot manner. We disclose herein the direct conversion of two different functionalities (alcohols and aldehydes) into esters (33 examples) with satisfactory yields, showing the potential of the developed catalyst toward varied oxidative organic transformations in a one-pot manner.

Palladium (II)-catalyzed C H bond functionalization of aromatic and heteroaromatic esters with acrylates under ligand-free conditions and their Anti-microbial evaluation

Palladium (II)-catalyzed C H bond functionalization of aromatic and heteroaromatic esters with acrylates under ligand-free conditions and their Anti-microbial evaluation

DFT study of the conformation, hydrogen bonds, IR, Raman, and NMR spectra of 1,3-disubstituted p-tert-butylthiacalix[4]arenes

The molecular design of spatially preorganized molecules is one of the critical issues in organic chemistry. Molecular recognition and multipoint binding define them. They organize nanoscale assemblies and devices and stably form host-guest inclusion complexes. Not only is this kind of research important in theory but it also has applications. They are used to create the basic elements of sensory devices: elements of cellular electronics, functional nanofilms and coatings, molecular switches, etc. Thiacalix[4]arenes are a useful molecular platform for constructing a wide range of preorganized receptor structures. This research aims to examine the structure and spectra of distally substituted para-tert-butylthiacalix[4]arene aliphatic (C1) and aromatic (C2) esters. The comparison of the spectra of C1, C2, and C3 makes it possible to reveal the structures and H-bonds of these compounds. The structures and H-bonds of these compounds can be seen by analyzing the spectra of C1, C2, and C3. Calculations were made for the spectra of various C1 and C2 molecule conformations. The most stable conformation for C1 and C2 molecules is a distorted cone 2 (DC2) with the same ester group orientation. The pinched cone (PC) conformation is the most unstable. Thiacalixarene molecules' cavities shrink from 3.61 to 3.57Å when aromatic ester groups take the place of aliphatic ester groups. Two OH groups are linked to an oxygen atom in the DC1 and DC2 conformations of the C1 and C2 molecules. H-bonds in C1 and C2 molecules affect the supramolecular characteristics of these molecules. A drop in ionization energy and increases in electron affinity, chemical potential, softness, electrophilicity index, and dipole moment occur when aliphatic esters are replaced with aromatic ones. Disubstituted aliphatic and aromatic esters' IR, Raman, and NMR spectra have been investigated. The DFT/B3LYP/6-311G(d,p) method and the GAUSSIAN 09W software were used to determine the vibrational spectra of molecules and optimize their geometry. A gauge-independent (GIAO) approach was used to determine chemical shifts in the NMR spectra with respect to tetramethylsilane.

Investigation on selective separation of oxygen-containing compounds in lignite and sub-bitumite

To realize the high value-added utilization of low-rank coal and elucidate the selectivity of solvent structure and oxygen-containing compounds in low-rank coal, Zhaotong (ZT) lignite and Naomaohu (NMH) sub-bitumite were subjected to thermal dissolution in three types of oxygen-containing solvents with different properties, namely ethanol (ET), tetrahydrofuran (THF) and ethyl acetate (EA). The soluble portions (SPs) obtained were separated by column chromatography into three types of fractions: hydrocarbon (HY), non-hydrocarbon (NHY) and asphaltene (ASP). The results indicated that the yields of SPs in all three solvents for each coal was ET > THF > EA, and the ratios of column chromatographic fractions of SPs of the two coals were significantly different, with lower asphaltene content in the SPs of NMH. The thermal dissolution process of the three solvents significantly reduced the oxygen content of low-rank coal, and the deoxygenation capacity was in the order of ET > THF > EA. More medium or low polarity compounds could be obtained from NMH than from ZT through thermal dissolution process. ET showed excellent selectivity for the generation of both phenols and esters, where the phenols were mainly alkylphenols. THF could release highly condensed polycyclic compounds from coal thus more naphthalenols containing substituent groups were detected in phenols. And it was more selective to COO bonds in NMH than ZT from the results of XPS. More esters were detected in the SPs of NMH compared with ZT. EA had a strong selectivity for CO in low-rank coals, and the thermal dissolution process released a large number of esters, which could be divided into alkanoates and aromatic acid esters. This study can provide a theoretical basis for extracting high value-added chemicals from low-rank coal under mild conditions.

Synthesis and Properties of Sucrose- and Lactose-Based Aromatic Ester Surfactants as Potential Drugs Permeability Enhancers.

The delivery of therapeutics across biological membranes (e.g., mucosal barriers) by avoiding invasive routes (e.g., injection) remains a challenge in the pharmaceutical field. As such, there is the need to discover new compounds that act as drug permeability enhancers with a favorable toxicological profile. A valid alternative is represented by the class of sugar-based ester surfactants. In this study, sucrose and lactose alkyl aromatic and aromatic ester derivatives have been synthesized with the aim to characterize them in terms of their physicochemical properties, structure-property relationship, and cytotoxicity, and to test their ability as permeability enhancer agents across Calu-3 cells. All of the tested surfactants showed no remarkable cytotoxic effect on Calu-3 cells when applied both below and above their critical micelle concentration. Among the explored molecules, lactose p-biphenyl benzoate (URB1420) and sucrose p-phenyl benzoate (URB1481) cause a reversible ~30% decrease in transepithelial electrical resistance (TEER) with the respect to the basal value. The obtained result matches with the increased in vitro permeability coefficients (Papp) calculated for FTIC-dextran across Calu-3 cells in the presence of 4 mM solutions of these surfactants. Overall, this study proposes sucrose- and lactose-based alkyl aromatic and aromatic ester surfactants as novel potential and safe permeation enhancers for pharmaceutical applications.