Ester C Research Articles

A comprehensive study on fermentation and aroma contributions of Torulaspora delbrueckii in diverse wine varieties: Insights from pure and co-fermentation studies

As a well-commercialized and utilized non-Saccharomyces yeast, Torulaspora delbruineckii is gaining increasing relevance in the winemaking industry. However, its ability to produce distinctive aromas in wine has been inconsistently reported in the literature. This study aimed to evaluate the fermentation performance and aroma properties of T. delbrueckii isolates through pure and co-fermentation with Saccharomyces cerevisiae across eight different wine varieties: Merlot, Zidaifu, Petit Verdot, Marselan, Italian Riesling, Sauvignon Blanc, Ugni Blanc, and Petit Manseng. A comprehensive analysis using HS-SPME-GC–MS, OPLS-DA, and Spearman’s correlation analysis was conducted. Key findings include: (1) The strain T. delbrueckii R12 exhibited higher extracellular enzyme activity compared to S. cerevisiae CECA and demonstrated superior sugar tolerance compared to six other native T. delbrueckii strains. (2) T. delbrueckii R12 exhibited strong fermentative capability, completing fermentation in 23 days across the eight wines, producing lower levels of acetic acid (0 ∼ 0.8 g/L reduction) and ethanol (0.1 ∼ 4.0 % v/v reduction), and higher levels of glycerol (0.1 ∼ 0.9 g/L increase) in the majority of wines. (3) Co-fermentation with T. delbrueckii and S. cerevisiae altered glycosidase activity, enhancing the varietal aroma intensity and complexity of the eight wines by releasing C6 compounds, terpenes and esters, and reducing higher alcohols and fatty acids. (4) The aroma contribution of T. delbrueckii R12 was variety-dependent, with isobutyl alcohol, isopentyl alcohol, 1-pentanol, and 1-propanol prevalent in red wines, and (Z)-2-hexen-1-ol more associated with white wines. Additionally, T. delbrueckii R12 consistently enhanced aromas in all eight experimental wines by increasing levels of 1-hexanol, farnesyl alcohol, linalool, citronellol, ethyl acetate, isobutyric acid and decanoic acid, while decreasing 1-pentanol, octanoic acid, isoamyl acetate, and ethyl laurate. Seven of the increased compounds were identified as signature aromas of T. delbrueckii R12, potentially contributing grass, floral, muscat, rose, fruit, caramel and buttery notes to the wines. This study confirms the significant role of T. delbrueckii in winemaking and wine aroma, resolving previous discrepancies in the literature. It provides new knowledge for innovating and diversifying wine production across various grape varieties.

Influences of Cluster Thinning on Fatty Acids and Green Leaf Volatiles in the Production of Cabernet Sauvignon Grapes and Wines in the Northwest of China.

Cluster thinning has been widely applied in yield management and its effect on green leaf volatiles (GLVs) in wines has seldom been studied. GLVs are important flavor compositions for grapes and wines. This work aimed to investigate the impact of cluster thinning on these volatiles and their precursors in grapes and wines. Severe cluster thinning (CT1) and medium cluster thinning (CT2) were performed on Cabernet Sauvignon (Vitis vinifera L.) vines in two sites (G-farm and Y-farm) from Xinjiang province in the Northwest of China. The impact of cluster thinning treatments on the accumulation of GLVs and their precursors, long chain fatty acids (LCFAs) of grape berries and C6 volatiles, in resulting wines was investigated. Multivariate analysis showed that cluster thinning treatments induced significant changes in fruit and wine composition in both farms. In Y-farm, medium cluster thinning (CT2) significantly increased the average cluster weight of harvested berries. Additionally, both cluster thinning treatments (CT1 and CT2) increased fatty acids in harvested berries and CT2 led to an increase in C6 esters and a decrease in C6 alcohols in the wines of Y-farm under the warmer and drier 2012 vintage. However, the effect of cluster thinning was likely negative in G-farm due to its wetter soil and excessive organic matter. The treatments may be applicable for local grape growers to improve viticultural practices for the more balanced vegetative and reproductive growth of Cabernet Sauvignon grapevines. This work also provided further knowledge on the regulation of fatty acids and the derived C6 volatiles through the lipoxygenase (LOX) pathway.

Crucial Roles of Leaving Group and Open-Shell Cation in Photoreaction of (Coumarin-4-yl)methyl Derivatives.

Photoreactions of (coumarin-4-yl)methyl derivatives have been extensively studied in many fields of chemistry, including organic synthesis and photoinduced drug delivery systems. The identification of the reaction intermediates involved in the photoreactions is crucial not only for elucidating the reaction mechanism but also for the application of the photoreactions. In this study, the photoreactions of 7-diethylamino(coumarin-4-yl)methyl thioester 1a [-SC(O)CH3], thionoester 1b [-OC(S)CH3], and ester 1c [-OC(O)CH3] were investigated to clarify the intermediary species and their chemical behavior. While a radical pair [i.e., 7-diethylamino(coumarin-4-yl)methyl radical and CH3C(O)S•] plays an important role in the photoreactions of 1a and 1b, an ion pair [i.e., 7-diethylamino(coumarin-4-yl)methyl cation, and CH3CO2-] was the key in the photoreaction of 1c. 18O-isotope-labeling of 1c revealed a negligible recombination process within the ion pair. The unprecedented observation was rationalized by the open-shell character of the 7-diethylamino(coumarin-4-yl)methyl cation, whose formation was confirmed through product analysis and transient absorption spectroscopy.

Influence of Benzothiadiazole on the Accumulation and Metabolism of C6 Compounds in Cabernet Gernischt Grapes (Vitis vinifera L.).

Pre-harvest application of elicitors improves grape quality, specifically the phenolic compounds and color characteristics. Limited research has been conducted on the impact of elicitors on the C6 compounds found in grapes. This is due to lack of comprehensive studies examining the combined effects of bound aroma compounds, enzyme activity, and substrate availability. This study aimed to assess the impact of benzothiadiazole (BTH) on the physicochemical properties and C6 compounds of Cabernet Gernischt grapes during ripening. Compared with the control group (CK), BTH treatment significantly increased the 100-berry weight, skin/berry ratio, pH, total phenolic content, and total flavonoid content in ripe grapes. Additionally, BTH treatment led to significant reductions in reducing sugar, total soluble solids, titratable acidity, linoleic acid, linolenic acid, and free C6 aldehydes. Furthermore, BTH treatment significantly decreased the contents of free C6 alcohols and increased the levels of free and bound C6 esters. BTH treatment also increased the activities of lipoxygenase, alcohol dehydrogenase, and alcohol acetyltransferase enzymes, while it decreased the activity of hydroperoxide lyase enzyme. The application of BTH resulted in changes to the physicochemical properties and levels of C6 compounds in Cabernet Gernischt grapes by up-regulating enzyme activity and down-regulating precursors.

Synthesis and Characterization of Edaravone Analogues as Remyelinating Agents and Putative Mechanistic Probes.

Edaravone (EDA), an antioxidant drug approved for the treatment of ischemic stroke and amyotrophic lateral sclerosis, was recently proposed as a remyelinating candidate for the treatment of multiple sclerosis. Here, we synthesized twelve EDA analogues 2b-4c showing three substitution patterns A-C, searching for improved remyelinating agents and putative molecular targets responsible for their regenerative activity. We profiled them in three primary assays to determine their stimulation of oligodendrocyte progenitor cell metabolism (tetrazolium MTT assay), their antioxidant potential (2,2-diphenyl-1-picrylhydrazyl-DPPH assay) and to predict their bioavailability (virtual ADME profile). Active 4'-carboxylate 2b, 4'-ester 2c and N1-carbamate-4'-ester 4a were further characterized, justifying their in vitro effects and selecting 4a as a putative EDA 1 prodrug suitable for in vivo testing.

Characterization of volatile compounds of Gök Üzüm raisins produced from grapes pre-treated with different dipping solutions

BackgroundRaisins contain a wide range of secondary metabolites, including volatile compounds that may contribute to the health benefits and preference of consumers. To our knowledge, this is one of the first studies concerning the analysis of volatile compounds in raisin. The goal of this study was to compare volatile composition of Gök Üzüm (Vitis vinifera L.) raisins produced from grapes dried before the application of two pre-treatments solutions: wood ash (WA) and potassium carbonate (K2CO3).ResultsGök Üzüm raisins produced from grapes dipped into the WA solution presented higher contents of most of the studied volatile compounds (including the total contents of C6 compounds, alcohols, benzenoids, esters, aldehydes, terpenes and C13 norisoprenoids) and lower contents of (Z)-2-hexenol and 2-hexenoic acid than the raisins produced from grapes dipped into K2CO solutions. Gök Üzüm raisins were characterized by fruity, floral and grass aromas according to their odor activity values. Drying Gök Üzüm grapes after the treatment of WA solutions promotes a higher aromatic composition compared to K2CO solutions.ConclusionThese findings can greatly assist raisin producers in deciding which dipping solution to use before using a dipping solution to dry the grapes.Graphical

Photochemical and Single Electron Transfer Generation of 2'-Deoxycytidin-N4-yl Radical from Oxime Esters.

A 2'-deoxycytidin-N4-yl radical (dC·), a strong oxidant that also abstracts hydrogen atoms from carbon-hydrogen bonds, is produced in a variety of DNA damaging processes. We describe here the independent generation of dC· from oxime esters under UV-irradiation or single electron transfer conditions. Support for this σ-type iminyl radical generation is provided by product studies carried out under aerobic and anaerobic conditions, as well as electron spin resonance (ESR) characterization of dC· in a homogeneous glassy solution at low temperature. Density functional theory (DFT) calculations also support fragmentation of the corresponding radical anions of oxime esters 2d and 2e to dC· and subsequent hydrogen atom abstraction from organic solvents. The corresponding 2'-deoxynucleotide triphosphate (dNTP) of isopropyl oxime ester 2c (5) is incorporated opposite 2'-deoxyadenosine and 2'-deoxyguanosine by a DNA polymerase with approximately equal efficiency. Photolysis experiments of DNA containing 2c support dC· generation and indicate that the radical produces tandem lesions when flanked on the 5'-side by 5'-d(GGT). These experiments suggest that oxime esters are reliable sources of nitrogen radicals in nucleic acids that will be useful mechanistic tools and possibly radiosensitizing agents when incorporated in DNA.

Investigating the Aromatic Compound Changes in Table Grape Varieties during Growth and Development, Using HS-SPME-GC/MS

This study aimed to identify the aromatic compounds present in the different aroma types of different table grape varieties and deeply understand the changes in the aromatic compounds during the growth and development process. The skin and flesh of three table grape varieties (‘Kyoho’, ‘Shine Muscat’, and ‘Ryuho’) in different growth and development stages were selected to determine their aromatic compounds using headspace solid-phase microextraction gas chromatography-mass spectrometry and principal component analysis. The results showed that the aromatic compounds of the ‘Kyoho’ and ‘Ryuho’ grapes were similar, mainly containing C6 compounds and esters, whereas ‘Shine Muscat’ was characterized by C6 compounds and terpenes. The levels of aromatic compounds in the skin were higher than those in the flesh. The content of esters in ‘Ryuho’ was significantly higher than that in ‘Kyoho’ and ‘Shine Muscat’. This showed that ‘Ryuho’ combines the advantages of the parents in its aroma composition. Selecting suitable parents for hybridization is one method for obtaining new varieties with a special aroma. This provides a theoretical basis for future molecular hybrid breeding and molecular-assisted breeding, as well as molecular biology research on aroma synthesis and metabolism in table grapes.

Impact of chemical structure on the in vitro hydrolysis of fatty esters of 2-ethylhexanoic acid or 2-ethylhexanol and extrapolation to the in vivo situation

Fatty esters of 2-ethylhexanoic acid (EHA) and 2-ethylhexanol (EH) are commonly used in cosmetics. Human liver and skin S9 and human plasma were used to determine the in vitro rates of clearance (CLint) of a series of compounds, with a range of 2–11 carbons on the acid or alcohol moiety and branching at the C2 position. The impact of carbon chain length on in vitro CLint was most prominent for the liver metabolism of esters of EH, while for in vitro skin metabolism it was greater for esters of EHA. The position of the branching also impacted the liver hydrolysis rates, especially for the C3, C4, and C5 esters with lower CLint in vitro rates for esters of EHA relative to those of EH. When the in vitro intrinsic clearance rates were scaled to in vivo rates of hepatic clearance, all compounds approximated the rate for hepatic blood flow, mitigating this dependence of metabolism on structure. This work shows how structural changes to the molecule can affect in vitro metabolism and, furthermore, allows for an estimation of the in vivo metabolism.

Alcohol Acyltransferase Is Involved in the Biosynthesis of C6 Esters in Apricot (Prunus armeniaca L.) Fruit.

Short-chain esters derived from fatty acid contribute to the characteristic flavor of apricot fruit, and the biosynthesis of these compounds in fruit is catalyzed by alcohol acyltransferase (AAT). In this work, we investigated the AAT gene family via genome-wide scanning, and three AAT loci were identified in different linkage groups (LGs), with PaAAT1 (PARG22907m01) in LG7, PaAAT2 (PARG15279m01) in LG4, and PaAAT3 (PARG22697m01) in LG6. Phylogenetic analysis showed that PaAAT1 belongs to clade 3, while PaAAT2 and PaAAT3 belong to clade 1 and clade 2, respectively. In contrast, the three AAT genes present different expression patterns. Only PaAAT1 exhibited distinct patterns of fruit-specific expression, and the expression of PaAAT1 sharply increased during fruit ripening, which is consistent with the abundance of C4–C6 esters such as (E)-2-hexenyl acetate and (Z)-3-hexenyl acetate. The transient overexpression of PaAAT1 in Katy (KT) apricot fruit resulted in a remarkable decrease in hexenol, (E)-2-hexenol, and (Z)-3-hexenol levels while significantly increasing the corresponding acetate production (p < 0.01). A substrate assay revealed that the PaAAT1 protein enzyme can produce hexenyl acetate, (E)-2-hexenyl acetate, and (Z)-3-hexenyl acetate when C6 alcohols are used as substrates for the reaction. Taken together, these results indicate that PaAAT1 plays a crucial role in the production of C6 esters in apricot fruit during ripening.

Selective Ammonolysis of Bioderived Esters for Biobased Amide Synthesis.

Amidation is an important reaction for bioderived platform molecules, which can be upgraded for use in applications such as polymers. However, fundamental understanding of the reaction especially in the presence of multiple groups is still lacking. In this study, the amidation of dimethyl fumarate, maleate, and succinate through ester ammonolysis was examined. The reaction networks and significant side reactions, such as conjugate addition and ring closing, were determined. A preliminary kinetic comparison among additional C4 and C6 esters showed a significant correlation between molecular structure and ammonolysis reactivity. Esters with a C=C double bond in the molecule backbone were found to have higher ammonolysis reactivity. To improve the selectivity to unsaturated amides rather than byproducts, the effects of thermal conditions and additives in dimethyl fumarate ammonolysis were examined. Lower temperature and decreasing methoxide ion concentration in the solution relative to the base case conditions increased the fumaramide selectivity from 67.1 to 90.6%.

Investigating the Individual Importance of the Pam2Cys Ester Motifs on TLR2 Activity

AbstractTLR2 agonists are at the forefront of vaccine research for a plethora of diseases, in particular they offer a promising tool for the treatment of cancer. A detailed knowledge of their structure–activity relationship informs the methodical design of vaccine constructs that include TLR2 agonists. Herein we report the design, synthesis, and biological evaluation of analogues of the TLR2 agonist Pam2Cys to further probe structure–activity relationships. These analogues replace one or other of the two ester groups with ether functionalities to elucidate the role of the carbonyls on TLR2 activity. Through this we demonstrate that the C3 ester carbonyl is dispensable, but the C2 carbonyl is essential for activity.

Influences of C5 esters addition on anti-knock and auto-ignition tendency of a gasoline surrogate fuel

The research octane numbers and auto-ignition characteristics of a toluene primary reference fuel (TPRF), when blended with three C5 esters, γ-valerolactone (GVL), methyl butanoate (MB), and methyl crotonate (MC), were investigated on a cooperative fuel research (CFR) engine and a constant volume combustion chamber (CVCC). In fuel preparation, ethanol was used to improve the miscibility, and the total additive comprised 1/3 ethanol and 2/3 GVL/MB/MC on a molar basis. The experimental results first reveal that the addition of the three series of additives boost fuel octane rating, and their boosting effects rank as MB &gt; GVL ∼ MC when fuels are blended on a molar basis. In contrast, the auto-ignition tendency of the three series of fuel blends, when blended on the molar basis, ranks as the MC blends &gt; the GVL blends&gt; the MB blends. Different from the similar reactivities observed for the MC blends and the GVL blends in the RON tests, the MC blends exhibit higher auto-ignition propensity than the GVL blends, probably because the higher enthalpy of vaporization of GVL causes a more significant cooling effect. Finally, different from the literature studies that reported similar reactivities for pure MB and MC, in this study MB shows lower reactivity than MC when blending with the TPRF gasoline surrogate.

C3 ester side chain plays a pivotal role in the antitumor activity of Maytansinoids

Maytansinoids, the chemical derivatives of Maytansine, are commonly used as potent cytotoxic payloads in antibody-drug conjugates (ADC). Structure-activity-relationship studies had identified the C3 ester side chain as a critical element for antitumor activity of maytansinoids. The maytansinoids bearing the methyl group at C3 position with D configuration were about 100 to 400-fold less cytotoxic than their corresponding L-epimers toward various cell lines. The detailed mechanism of how chirality affects the anticancer activity remains elusive. In this study, we determined the high-resolution crystal structure of tubulin in complex with maytansinol, L-DM1-SMe and D-DM1-SMe. And we found the carbonyl oxygen atom of the ester moiety and the tail thiomethyl group at C3 side chain of L-DM1-SMe form strong intramolecular interaction with the hydroxyl at position 9 and the benzene ring, respectively, fixing the bioactive conformation and enhancing the binding affinity. Additionally, ligand-based and structure-based virtually screening methods were used to screen the commercially macrocyclic compounds library, and 15 macrocyclic structures were picketed out as putatively new maytansine-site inhibitors. Our study provides a possible strategy for the rational discovery of next-generation maytansine site inhibitors.

Triterpenoids and Semisynthetic Derivatives with Antimicrobial Activities from the Leaves of &amp;lt;i&amp;gt;Caloncoba glauca&amp;lt;/i&amp;gt; (Flacourtiaceae)

Chemical investigation of the MeOH extract from the leaves of C. glauca yielded nine known triterpenoids (1-9) belonging to the cycloartane and friedelane series. Two of these compounds namely glaucartanoic acid A (1) and 3β,21β-dihydroxy-30-nor-(D:A)-friedoolean-20(29)-en-27-oic acid (5) were subjected to chemical derivatizations and afforded five new derivatives: diacetylglaucartanoic acid A (1a), 24-acetylglaucartanoic acid A (1b), glaucartanoic acid A methyl ester (1c), 24-methoxyglaucartanoic acid A methyl ester (1d), and 3β,21β-diacetoxy-30-nor-(D:A)-friedoolean-20(29)-en-27-oic acid (5a). Their structures were assigned based on their NMR and MS data and by comparison with literature values. The MeOH extract, isolated compounds and some new semi-synthetic derivatives were subjected to in vitro antimicrobial assays against a panel of pathogenic microorganisms, including Gram-positive and Gram-negative bacteria, and fungi using broth microdilution method. The MeOH extract displayed activity towards all the tested pathogenic bacterial and fungal strains with good activity (MIC against Staphylococcus aureus ATCC25923 and Shigella flexneri SDINT. Compounds 3 and 5 showed the most potent antimicrobial effect.

Development of volatile organic compounds and their glycosylated precursors in tamarillo (Solanum betaceum Cav.) during fruit ripening: A prediction of biochemical pathway

Key metabolites and flavour-regulation pathways in tamarillo were investigated to explore the development of free and glycosylated volatile organic compounds (VOCs) during fruit maturation. The concentrations of free and bound VOCs were determined by gas chromatography-mass spectrometry analysis. Changes of physical parameters, concentrations of flavour precursors, and activities of key endogenous enzymes were also monitored. A total of 22 free VOCs were identified with C6 alcohols and esters being the major compounds. From the 83 glycosylated VOCs detected, phenols and terpenoids were the dominant components. The concentration of total bound VOCs increased up to 4 times during fruit ripening. Lipoxygenase pathway is confirmed as an important biosynthetic mechanism for the generation of free and glycosylated VOCs during tamarillo ripening. This biosynthesis pathway is highly correlated with the activities of key enzymes and the contents of substrates, especially linolenic acid (p < 0.05 or p < 0.01).

Remote Participation during Glycosylation Reactions of Galactose Building Blocks: Direct Evidence from Cryogenic Vibrational Spectroscopy.

The stereoselective formation of 1,2‐cis‐glycosidic bonds is challenging. However, 1,2‐cis‐selectivity can be induced by remote participation of C4 or C6 ester groups. Reactions involving remote participation are believed to proceed via a key ionic intermediate, the glycosyl cation. Although mechanistic pathways were postulated many years ago, the structure of the reaction intermediates remained elusive owing to their short‐lived nature. Herein, we unravel the structure of glycosyl cations involved in remote participation reactions via cryogenic vibrational spectroscopy and first principles theory. Acetyl groups at C4 ensure α‐selective galactosylations by forming a covalent bond to the anomeric carbon in dioxolenium‐type ions. Unexpectedly, also benzyl ether protecting groups can engage in remote participation and promote the stereoselective formation of 1,2‐cis‐glycosidic bonds.

Evolution of volatile compounds during the development of Muscat grape ‘Shine Muscat’ (Vitis labrusca × V. vinifera)

This study investigated the evolution of both free and bound volatile compounds in ‘Shine Muscat’ grape from post-fruit set to post-maturity and limiting factors of the lipoxygenase (LOX) pathway. C6 compounds and terpenes were the main free and bound volatile compounds, respectively. At pre-softening, volatile compounds concentrations were mainly regulated by expansion dilution, and terpene concentrations decreased significantly, which resulted in the minimum terpene concentrations occurred at softening. The volatile compounds were mainly regulated by metabolic synthesis at post-softening, and the production of C6 compounds, terpenes and esters largely began at 10, 12 weeks post-flowering and maturity stages, respectively. In the LOX pathway, LOX, alcohol dehydrogenase and the substrate alcohols were the limiting factors. The aroma maturity stages occurred at 15.4 weeks post-flowering. Finally, the developmental patterns of the volatile compounds in grape were summarized considering previous results in neutral and non-Muscat aromatic varieties.

Brevifoliol ester induces apoptosis in prostate cancer cells by activation of caspase pathway.

Prostate cancer is fourth most abundant cancer type around the globe. Brevifoliol, a rearranged taxoid from Taxus walllichiana needles has been derivatized as C5 esters using Steglich esterification reaction. Seventeen diverse analogues were evaluated against a panel of human cancer cell lines by MTT assay. Among these, two of the semi-synthetic analogues, that is, 13 and 16 exhibited potent cytotoxicity, selectively against PC-3, prostate cancer cell lines. In cell cycle analysis, analogue 13 induced S and G2/M phase arrest and induced apoptosis by activating caspase-3. Compound 13 showed moderate efficacy in in-vivo Ehrlich ascites carcinoma in Swiss albino mice. Further, compound 13 was found to be safe in Swiss albino mice up to 1,000mg/kg dose in acute oral toxicity. Brevifoliol ester 13 may further be optimized for better efficacy.

Novel Liposomal Azido Mannosamine Lipids on Metabolic Cell Labeling and Imaging via Cu-Free Click Chemistry.

In comparison with the popular Ac4ManNAz applied as cell labels via Cu-free click chemistry, two novel azido mannosamine lipids with C6 and C12 esters on anomeric hydroxyl groups were prepared and encapsulated in a liposome delivery system, which enhanced chemical stabilities and showed good cell-metabolizable labeling efficiency on MDA-MB-231 cells with strong fluorescence after the treatment of DBCO-Cy5 by triazole formation via click chemistry.