Ethyl Glucoside Research Articles

Tandem catalytic conversion of glucose and cellobiose to 5-ethoxymethylfurfural with record yields

The conversion of biomass-derived carbohydrates to 5-ethoxymethylfurfural (EMF) is a fascinating reaction with 100% carbon atom utilization. Although effective conversion of 5-hydroxymethylfurfural (HMF) and fructose to EMF have been achieved, the direct conversion of glucose only gave low EMF yields. Herein, we reveal that the combinations of common Lewis acid with Brønsted acid in ethanol universally catalyze rapid etherification of glucose to intractable ethyl glucoside (EGL), as impedes the further conversion toward the desired products. The synergy of large-pore tin phosphate (SnPO) bearing strong Lewis acidic sites with acidic ionic liquid 1-(4-sulfobutyl)-3-methylimidazolium chloride (BSO3HMIMCl) enable tandem catalytic conversion of glucose, cellobiose and starch to EMF with record yields (61.7%, 61.8% and 55.7%, respectively), far exceeding previous reports. This transformation probably occurs via multiple parallel pathways, where water molecules generated by dehydration cooperate with acid and Cl- to hydrolyze EGL back to glucose, thus forming a positive feedback on EMF production.

Activation of GABA type A receptor is involved in the anti-insomnia effect of Huanglian Wendan Decoction

Huanglian Wendan Decoction (HWD) is a traditional Chinese medicine (TCM) prescribed to patients diagnosed with insomnia, which can achieve excellent therapeutic outcomes. As positively modulating the γ-aminobutyric acid (GABA) type A receptors (GABAARs) is the most effective strategy to manage insomnia, this study aimed to investigate whether the activation of GABAARs is involved in the anti-insomnia effect of HWD. We assessed the metabolites of HWD using LC/MS and the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database and tested the pharmacological activity in vitro and in vivo using whole-cell patch clamp and insomnia zebrafish model. In HEK293 cells expressing α1β3γ2L GABAARs, HWD effectively increased the GABA-induced currents and could induce GABAAR-mediated currents independent of the application of GABA. In the LC-MS (QToF) assay, 31 metabolites were discovered in negative ion modes and 37 metabolites were found in positive ion modes, but neither three selected active metabolites, Danshensu, Coptisine, or Dihydromyricetin, showed potentiating effects on GABA currents. 62 active metabolites of the seven botanical drugs were collected based on the TCMSP database and 19 of them were selected for patch-clamp verification according to the virtual docking simulations and other parameters. At a concentration of 100 μM, GABA-induced currents were increased by (+)-Cuparene (278.80% ± 19.13%), Ethyl glucoside (225.40% ± 21.77%), and β-Caryophyllene (290.11% ± 17.71%). In addition, (+)-Cuparene, Ethyl glucoside, and β-Caryophyllene could also serve as positive allosteric modulators (PAMs) and shifted the GABA dose-response curve (DRC) leftward significantly. In the PCPA-induced zebrafish model, Ethyl glucoside showed anti-insomnia effects at concentrations of 100 μM. In this research, we demonstrated that the activation of GABAARs was involved in the anti-insomnia effect of HWD, and Ethyl glucoside might be a key metabolite in treating insomnia.

Ultrasonication assisted percolation extraction, isolation, identification and in silico studies of secondary metabolites from Caesalpinia bonduc (L.) Roxb. seeds with special reference to the target proteins involved in Benign Prostatic Hyperplasia

Medicinal plant-derived phytochemicals provide a vast pool of diverse bioactive compounds for novel drug development. Caesalpinia bonduc L. Roxb. is a traditional medicinal plant that is reported for diverse pharmacological properties. This study aims to compare conventional (maceration) and novel extraction techniques (ultrasonication assisted maceration extraction) to evaluate their efficiency, yield and bioactive potential of hydroalcoholic extracts from C. bonduc seeds. Furthermore, the study also aimed to isolate the bioactive compounds from the hydroalcoholic seed extract obtained from ultrasonication assisted maceration and in-silico studies of isolated compounds against the protein targets involved in Benign Prostatic Hyperplasia (BPH). For comparing the influence of extraction methods, the seeds were extracted using a novel and conventional techniques. Chemical profiling, antioxidant activities, cytotoxic and apoptotic studies were conducted using obtained extracts. The extract yielded from the novel technique recorded the highest yield, significant antioxidant activity, cytotoxicity and chemical content when compared to the conventional technique. From the hydroalcoholic extract, three major bioactive compounds, namely ethyl glucoside, methyl lineolate and linoleic acid, were isolated using column chromatography. The structures of the compounds were elucidated on the basis of extensive NMR (1H, 13C, DEPT, 2D NMR- HMBC and HSQC) and HR-ESI-MS analysis. In-silico anti-BPH activity of isolated compounds clearly reveals that the compounds were targeting 5α‒Reductase and α1-Adrenoceptor linked to the BPH progressions. Based on this investigation, it is demonstrated that isolated molecules or active molecule-enriched fractions of C. bonduc should be further researched to confirm the anti-BPH activity through in-depth preclinical and clinical research for the development of products. Ethyl glucoside and methyl lineolate were isolated for the first time from C. bonduc.

Comparative analysis of functional components in Sakekasu (Sake lees)

Background:Sake lees (Sakekasu), a byproduct of sake production, has been recently attracting attention as a functional food. Sakekasu is rich in nutrients and contains glycerophosphocholine (GPC) and S-adenosylmethionine (SAM), which are well-known functional compounds. The content of these compounds in Sakekasu depends on a variety of factors, including fermentation conditions, especially the method and length of ripening. These differences are reflected prominently in the color of Sakekasu, which becomes darker due to the long ripening period and high drying temperature. Objective: This study aimed to clarify the contents of functional components in Sakekasu with different color tones (i.e., ripening period).Methods:Three types of Sakekasu with different color tones (white, ocher, and brawn) were collected from several breweries. The contents of multiple functional components in their extracts were determined by liquid chromatography coupled to high resolution ion-trap/time-of-flight mass spectrometry.Results: Sakekasu with white color had more abundant GPC, SAM, and fatty acids than those with darker color. However, ethyl glucoside and glyceryl glucosides did not differ significantly by color tone. Furthermore, the Maillard reaction products of sugar and dipeptide were mainly found in dark-colored Sakekasu, and their structures were annotated by tandem mass spectrometry.Conclusions:This study has clarified many functional compounds in Sakekasu in relation to color tone (i.e., ripening period) and highlighted the potential of Sakekasu with white color tone as a functional food.Keywords: Sakekasu, functional components, glycerophosphocholine, S-adenosylmethionine, tandem mass spectrometer

A process insight into production of ethyl levulinate via a stepwise fractionation

Ethyl levulinate (EL) is a key biomass-derived compounds due to its socio-economic benefits for the synthesis of commodity chemicals. Herein, we proposed an efficient one-step bamboo conversion to EL in ethanol, and a novel stepwise fractionation to purify EL and lignocellulose degradation products. A proton acid, due to its high catalytic efficiency, yielded 26.65 % EL in 120 min at 200 °C. The productions of ethyl glucoside and 5-ethoxymethylfurfural were analyzed in terms of by-products formation. To the best of our knowledge, there is no single report on catalyst for one step synthesis of EL directly from bamboo, as well as a stepwise fractionation to purify EL. Due to similar physiochemical properties in each fraction, the platform molecules could broaden a new paradigm of bamboo biomass utilization for renewable energy and value-added biochemicals. In addition, glucose, ethyl glucoside, corn starch, and microcrystalline cellulose were also investigated as substrates, so that the reaction intermediates of this one-pot procedure were identified and a possible reaction mechanism was proposed.

Xenobiotic metabolites modify immune responses of the cervicovaginal epithelium: potential mechanisms underlying barrier disruption.

Xenobiotic metabolites are exogenous biochemicals that can adversely impact reproductive health. We previously identified xenobiotics in cervicovaginal fluid during pregnancy in association with short cervix. In other organ systems, xenobiotics can modify epithelial barrier function. We hypothesise that xenobiotics dysregulate epithelial cell and macrophage immune responses as a mechanism to disrupt the cervicovaginal barrier. In vitro cell culture system. Laboratory within academic institution. Vaginal, ectocervical and endocervical epithelial cell lines and primary macrophages. Cells were treated with diethanolamine (2.5 mM), ethyl glucoside (5 mM) or tartrate (2.5 mM) for 24 h. Cytokines and matrix metalloproteinases were measured in cell supernatants (n = 3 per condition). One-way analysis of variance (ANOVA) with Dunnett's test for multiple comparisons was performed. Diethanolamine induces inflammatory cytokines, whereas ethyl glucoside and tartrate generally exert anti-inflammatory effects across all cells. Diethanolamine increases interleukin 6 (IL-6), IL-8, interferon γ-induced protein 10 kDa (IP-10), growth-regulated oncogene (GRO), fractalkine, matrix metalloproteinase 1 (MMP-1), MMP-9 and MMP-10 (p < 0.05 for all), factors involved in acute inflammation and recruitment of monocytes, neutrophils and lymphocytes. Ethyl glucoside and tartrate decrease multiple cytokines, including RANTES and MCP-1 (p < 0.05 for all), which serve as chemotactic factors. Vaginal cells exhibit heightened inflammatory tone compared with cervical cells and macrophages, with a greater number of differentially expressed analytes after xenobiotic exposure. Xenobiotic metabolites present in the cervicovaginal space during pregnancy modify immune responses, unveiling potential pathways through which environmental exposures may contribute to the pathogenesis of cervical remodelling preceding preterm birth. Future work identifying xenobiotic sources and routes of exposure offers the potential to modify environmental risks to improve pregnancy outcomes.

Experimental study combined with density functional theory and molecular dynamics simulation on the mechanism of glucose alcoholysis reaction

AbstractThe reaction characteristics and mechanism of carbohydrates is important in exploring and developing suitable technology for biofuels and biochemical production from lignocellulosic biomass. In this study, experiments combined with density functional theory (DFT) calculation and molecular dynamics (MD) simulation were used to investigate the glucose alcoholysis reaction mechanism catalyzed by extremely low concentrated sulfuric acid. The effects of temperature and tetrahydrofuran (THF) on the distribution of the product in the alcoholysis process of high‐concentration glucose were investigated. DFT calculation results showed that the addition of THF in ethanol can decrease the energy barrier of glucose degradation. Meanwhile, the MD simulation indicated that the catalyst tends to localize more around the glucose molecular, which was beneficial to the glucose degradation in ethanol. Combining the experimental and theoretical results, plausible glucose alcoholysis reaction pathways were proposed in this work. It was found that when temperature was lower than 190°C, the three main pathways were glucose conversion into ethyl glucoside (EDGP); glucose conversion into 1,6‐anhydro‐β‐d‐glucopyranose (LG), then further to levoglucosone (LGO), furans, or 1,4:3,6‐dianhydro‐α‐d‐glucopyranose (DGP); and glucose conversion to fructose. However, at higher temperatures (190 and 220°C), the main reaction pathways were, glucose conversion into LG, LGO, and ethyl levulinate (EL); glucose conversion into fructose, 5‐hydroxymethylfurfural (HMF), 5‐ethoxymethylfurfural (EMF), and EL; and glucose conversion into humins. DFT, MD simulation, and experimental results showed that the addition of THF is beneficial for the EDGP formation from high concentration glucose catalyzed by Brønsted acid.

Preterm birth is associated with xenobiotics and predicted by the vaginal metabolome

Spontaneous preterm birth (sPTB) is a leading cause of maternal and neonatal morbidity and mortality, yet its prevention and early risk stratification are limited. Previous investigations have suggested that vaginal microbes and metabolites may be implicated in sPTB. Here we performed untargeted metabolomics on 232 second-trimester vaginal samples, 80 from pregnancies ending preterm. We find multiple associations between vaginal metabolites and subsequent preterm birth, and propose that several of these metabolites, including diethanolamine and ethyl glucoside, are exogenous. We observe associations between the metabolome and microbiome profiles previously obtained using 16S ribosomal RNA amplicon sequencing, including correlations between bacteria considered suboptimal, such as Gardnerella vaginalis, and metabolites enriched in term pregnancies, such as tyramine. We investigate these associations using metabolic models. We use machine learning models to predict sPTB risk from metabolite levels, weeks to months before birth, with good accuracy (area under receiver operating characteristic curve of 0.78). These models, which we validate using two external cohorts, are more accurate than microbiome-based and maternal covariates-based models (area under receiver operating characteristic curve of 0.55–0.59). Our results demonstrate the potential of vaginal metabolites as early biomarkers of sPTB and highlight exogenous exposures as potential risk factors for prematurity.

Xenobiotic metabolites modify immune output of the cervicovaginal epithelium: potential mechanisms underlying barrier disruption

Xenobiotic metabolites are exogenous biochemicals that can adversely impact reproductive health. We previously identified xenobiotics in cervicovaginal (CV) fluid during pregnancy in association with spontaneous preterm birth (sPTB). Suggesting bioactive potential, in vitro data reveal that these xenobiotics can modify CV epithelial barrier function. We hypothesize that xenobiotics dysregulate epithelial immune output as a mechanism to disrupt the CV barrier. Vaginal (VK2), ectocervical (Ecto), and endocervical (Endo) cell lines were treated with xenobiotics diethanolamine (DEA, 2.5mM), ethyl glucoside (EG, 5mM), tartrate (TA, 2.5mM) for 24 hours. A 41-plex cytokine Luminex panel and 5-plex matrix metalloproteinase (MMP) Luminex panel were run on cell media (n=3 per condition). Data were analyzed with a five-parameter logistic curve. One-way ANOVAs with Dunnett’s multiple comparisons tests were performed. DEA induces inflammatory cytokines while EG and TA generally exert anti-inflammatory effects across all cells (Fig. 1). DEA upregulates IL-6, IL-8, IP-10, MCP-1, GRO, fractalkine, MMP-1, MMP-9, and MMP-10 (p< 0.05 for all), factors involved in acute inflammation and recruitment of monocytes, neutrophils, and lymphocytes. EG and TA downregulate multiple cytokines, including RANTES and MCP-1 (p< 0.05 for all), which serve as chemotactic factors. VK2 cells exhibit higher inflammatory tone compared to cervical cells, with approximately twice the number of differentially detected cytokines after xenobiotic treatment. Cervical cells demonstrate similar immunologic responses to xenobiotics compared to VK2 cells. Xenobiotic metabolites present in the CV space during pregnancy modify epithelial immune output, unveiling potential immunologic pathways through which environmental exposures may contribute to the pathogenesis of cervical remodeling preceding sPTB. Future work identifying exogenous sources of these xenobiotics is warranted and offers potential to modify aspects of the environment to improve pregnancy outcomes. SMFM/AAOGF (KG), 5R01NR014784 (ME)

Diagnostic meaning of urinary ethyl glucoside concentrations in relationship to alcoholic beverage consumption

Incidents and accidents often involve the drinking of alcoholic beverages. We investigated compounds that indicate the consumption of alcoholic beverages even after ethanol (EtOH) becomes undetectable in blood and urine. Ethyl glucoside (EG) has been isolated as a possible drinking marker, and a GC–MS/MS method for EG isomers has been developed. EG isomers in several alcoholic beverages were analyzed. In sake, only αEG was observed in high concentrations. In wine and beer, both α and βEG were detected. Whisky, however, did not contain EG. EtOH and EG concentrations were analyzed in urine up to 48 h after ingestion. Maximum EtOH concentrations were reached in 1–2 h and was mostly eliminated in 6 h. Maximum EG concentrations were reached in 3–6 h, gradually decreased, and remained low after 24 h. After drinking sake, the αEG concentrations were much higher than that of other alcoholic beverages. After drinking wine or beer, βEG was detected, but lower than αEG. Also, αEG was detected in urine after drinking whisky that contained no EG. This suggested that αEG may be synthesized in vivo. Disaccharide-degrading enzymes such as α-glucosidase are present in the human small intestine. It was considered that αEG was synthesized when alcohol was consumed with certain foods, such as carbohydrates. In actual forensic autopsy cases, EtOH and EG isomer analysis provided useful information regarding drinking history. In conclusion, it is considered that urinary EG isomers can be used as drinking markers that complement EtOH analysis.

Solvothermal conversion of spent aromatic waste to ethyl glucosides

On-farm extraction of commercially important essential oil from aromatic crops generates huge spent aromatic waste. This massive waste is often disposed in the unregulated landfills or burned in the open air to vacate the fields. Hence, a new method for processing of aromatic spent waste has been developed to obtain platform chemicals, such as, xylose and ethyl glucosides. The thermochemical liquefaction of acid pre-treated palmarosa (cymbopogon martini) biomass furnished a mixture of ethyl glucopyranosides in good yield (∼17 wt% relative to biomass) and selectivity (∼77%) by heating with p-cymen-2-sulphonic acid (p-CSA) in the presence of ethanol as a solvent. The detection, quantification and isolation of ethyl glucosides may provide a new application of spent aromatic biomass for use as a feed stock in the production of value added chemicals.

A validated method for the separation of ethyl glucoside isomers by gas chromatography-tandem mass spectrometry and quantitation in human whole blood and urine

Ethyl glucoside (EG) is present in Japanese sake in high concentrations, and can be found in other alcoholic beverages like beer and wine in varying amounts. EG exists as alpha (α) and beta (β) isomers, and the concentrations and ratios of these isomers differ depending on the alcoholic beverage. Herein, we report a validated analysis method for the separation of EG isomers in human whole blood and urine, by GC–MS/MS. Whole blood and urine samples were deproteinized and interferences removed by weak cation exchange cartridges. The target analytes were acetylated using acetic anhydride and pyridine by microwave-accelerated derivatization. Separation was performed using tandem columns, with detection in the multiple reaction monitoring (MRM) mode. The MRM transitions for all compounds were m/z 157.0 > 115.1 for the quantifying transition, and m/z 157.0 > 73.1 and m/z 141.0 > 81.0 for the qualifying transitions. Assay validation included linearity, LOD and LLOQ, bias, within-run and between-run precision, stability, and dilution integrity. Baseline separation of the 2 isomers was achieved with linear calibration (r2 > 0.99) across the calibration range 0.625 to 50 μg/mL for both α- and β-EG in both whole blood and urine. The validated method was then applied to actual human whole blood and urine samples collected at autopsy, as well as relevant alcoholic beverage samples. The quantitation of EG isomers could benefit the forensic toxicology community by acting as markers for recent alcoholic beverage consumption.

Understanding the role of the substrate and the metal triflate acidic catalyst in sugar platform biorefineries: A comprehensive systematic approach to catalytic transformations of (poly)carbohydrates in ethanol

We systematically explore a range of model conversions of mono- and disaccharides, and of linear and branched polysaccharides under the catalytic action of metal trifluoromethanesulfonates (metal triflates) in ethanol. This highlights the preferred reactivity of specific (poly)carbohydrates, and the interplay between selectivities of the reactions and the dominating catalyst activity (Brønsted or Lewis). It unambiguously delineates that selectivities of acid-catalysed transformations of (poly)carbohydrates into value added platform chemicals rely on the origin of the substrate, any (pre)treatment, the acidic catalyst, and the reaction conditions. The optimised catalytic systems enable very efficient conversion of cellulosic carbohydrates into significantly value added ethyl glucosides (yields up to 63%), ethyl xylosides (yields up to 69%), ethyl levulinate (yields up to 75%), ethyl lactate (yields up to 98%), ethoxyacetaldehyde diethylacetal (yields up to 33%), and furfural diethylacetal (yields up to 44%), depending on the substrate and reaction conditions.

Synthesis of 5-ethoxymethylfurfural from saccharides using combined metal–surfactant catalyst in ethanol/dimethyl sulfoxide

The synthesis of 5-ethoxymethylfurfural (EMF) from glucose using metal chlorides or combined metal–surfactant catalysts as Lewis acids in a solution of ethanol/dimethyl sulfoxide was investigated. Metal chlorides such as aluminum chloride and chromium(III) chloride mainly produced 5-hydroxymethylfurfural and ethyl glucoside in reactions at 140 °C for 180 min. However, the combined metal–surfactant catalysts aluminum tridodecyl sulfate (Al(DS)3) and chromium(III) tridodecyl sulfate efficiently improved the yield of EMF from glucose. The maximum yield of EMF using Al(DS)3 was 37.9% at 160 °C for 60 min. Moreover, the EMF yields from other saccharides (fructose, mannose, sucrose, cellobiose, and inulin) in the presence of Al(DS)3 as a catalyst ranged from 31.2 to 59.3%.

Phytochemicals isolated from the root bark of Sarcocephalus latifolius (Sm.) E.A.Bruce

Phytochemical investigation of the root bark of Sarcocephalus latifolius resulted in isolation and identification of eight compounds, including triterpenoid glycosides (1-4), ethyl glucoside (5), monoterpene indole alkaloids (6-7), and sterol (8). The structure elucidation of isolated compounds was achieved on the basis of NMR and mass spectral data. Compounds 2-5 were isolated for the first time from this genus and their chemotaxonomic significance was discussed.

Catalytic ethanolysis of microcrystalline cellulose over a sulfonated hydrothermal carbon catalyst

Abstract The catalytic ethanolysis of microcrystalline cellulose in supercritical ethanol is examined over a sulfonated hydrothermal carbon catalyst (SHTC). SHTC is amorphous carbon containing −OH, −COOH and −SO3H groups with total acidity of 7.15 mmol/g and −SO3H acidity of 1.72 mmol/g. SHTC shows high catalytic activity towards the ethanolysis of cellulose in supercritical ethanol. Complete conversion of microcrystalline cellulose with high yields of ethyl levulinate and ethyl glucoside is obtained. The reaction temperature, time and catalyst amount have significant effects on the catalytic performances of SHTC. Appropriate reaction time and less catalyst amount are favorable for the production of ethyl glucoside, while prolonged reaction time and appropriate catalyst amount favor the production of ethyl levulinate. The highest yield of ethyl glucoside as 420.9 mg/g cellulose is obtained over 0.1 g SHTC at 245 oC for 1 h. The highest yield of ethyl levulinate as 817.6 mg/g cellulose is achieved over 0.3 g SHTC at 245 oC for 1 h. SHTC shows good stability in the recycle experiments with slight loss of catalytic activity.

Magnetically recyclable cellulose-derived carbonaceous solid acid catalyzed the biofuel 5-ethoxymethylfurfural synthesis from renewable carbohydrates

A series of carbonaceous solid acid catalysts were prepared by facile carbonization and sulfonation of biorenewable feedstocks (i.e., glucose, sucrose, starch and cellulose), and employed for directly converting carbohydrates in ethanol medium to synthesize 5-ethoxymethylfurfural (EMF). The carbonization temperature of cellulose and starch (500 °C) was required to be higher than that of glucose and sucrose (400 °C) to realize high –SO3H density and EMF yield. Based on rich exploitability of cellulose and good activity of its derived carbonaceous catalyst, magnetic cellulose-derived carbonaceous solid acid (MCC-SO3H) was subsequently synthesized, which possessed a porous structure with BET surface area of 35.34 m2 g–1, high –SO3H density (1.28 mmol g–1) and sufficient magnetism for separation (1.99 emu g–1). By optimizing the process variables, a maximum EMF yield of 63.2% could be achieved from fructose at 120 °C, and ethyl levulinate formation was favored at elevated temperature. The MCC-SO3H catalyst could be readily separated from the reaction mixture by an external magnet with recovery rate of 92.6% after six successive runs, and reused repeatedly with little deactivation. Besides, this catalyst was efficient for the one-pot transformation of fructose-based polysaccharides into EMF, affording yields of 51.3% and 32.5% from inulin and sucrose, respectively. With glucose as the substrate, instead ethyl glucoside with a high yield of 86.5% was obtained.

An Insight into the Selective Conversion of Bamboo Biomass to Ethyl Glycosides

Selective conversion of lignocellulosic biomass to ethyl glycosides and other valued chemicals is an important step for biomass utilization. In this paper, directional liquefaction of bamboo biomass into ethyl glucosides and ethyl xylosides with acid in ethanol media was investigated. The ethyl glycoside distribution was found to depend mainly on the temperature and the amount of H2SO4. Under a shorter reaction time of 30 min at a temperature of 180 °C, the maximum yield of ethyl glycoside and its derivatives was 40.86 wt % based on raw materials, with 16.07 wt % ethyl glucosides and 10.11 wt % ethyl xylosides, respectively. Additional studies with glucose and xylose as substrates have been conducted under temperatures of 100–200 °C. Ethyl glucosides (xylosides) isomers were favorable during the directional liquefaction process. The quantification of the separated content of ethyl glucosides and ethyl xylosides provides a new paradigm for the use of biomass as a raw material for renewable energy and chemi...

Insights into the Metal Salt Catalyzed 5-Ethoxymethylfurfural Synthesis from Carbohydrates

The use of common metal salts as catalysts for 5-ethoxymethylfurfural (EMF) synthesis from carbohydrate transformation was performed. Initial screening suggested AlCl3 as an efficient catalyst for EMF synthesis (45.0%) from fructose at 140 °C. Interestingly, CuSO4 and Fe2(SO4)3 were found to yield comparable EMF at lower temperature of 110 to 120 °C, and high yields of ethyl levulinate (65.4–71.8%) were obtained at 150 °C. However, these sulfate salts were inactive in EMF synthesis from glucose and the major product was ethyl glucoside with around 80% yield, whereas EMF of 15.2% yield could be produced from glucose using CrCl3. The conversion of sucrose followed the accumulation of the reaction pathways of fructose and glucose, and a moderate yield of EMF could be achieved.

Acidic mesostructured silica-carbon nanocomposite catalysts for biofuels and chemicals synthesis from sugars in alcoholic solutions

Sulfonated mesostructured silica-carbon nanocomposites with varying carbon content, acidic site density and porosity, obtained via the one-pot evaporation induced self-assembly (EISA) synthesis, were used here to convert sugars into useful chemicals and biofuel components in alcoholic solvent. The nanocomposites show a remarkable catalytic performance in ethanol, yielding up to 80%, predominantly ethyl levulinate, 5-ethoxymethylfurfural and 2-(diethoxymethyl)-5-(ethoxymethyl)furan. Fructose is the sugar substrate of choice, but the sulfonated composites are also able to convert di- and polymeric forms of fructose. Due to a lack of a glucose-to-fructose isomerization ability, the composites are unable to form the above products from the glucose resources (glucose and cellulose), ethyl glucoside being the dominant product from these feedstocks. The composite has a peculiar hierarchical pore architecture, which is stable on shelf in ambient for at least six years. While the mesoporosity facilitates entrance and fast transport (even of soluble poly-carbohydrates like inulin and cellulose polymers), the presence of microporosity is beneficial to attain fast sugar catalysis. Since the microporosity is associated with voids in the carbon phase (preferably pyrolyzed at 400°C), composites with high carbon contents are preferred. Due to the fast transport, reactions with fructose in ethanol run in the chemical regime in the applied thermal conditions. Kinetic inspection of the reaction further clarifies the complex network of consequent and parallel reactions, demonstrating that HMF is the main precursor of humins, while the formation of EL directly from HMF should also be considered. While this observation corroborates the protective role of alcohols like ethanol, this work also concludes based on a series of reactions in different alcohols and water, that the presence of water plays a crucial role in the HMF-to-humins formation. While alcohols are known to stabilize HMF, the unprotected HMF is fairly stable in non-aqueous reaction circumstances like in tert-butanol solvent.