- Studies on kinetics and mechanism of oxidation of D-sorbitol and D-mannitol by cerium (IV) in aqueous micellar sulfuric acid media
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The kinetics and mechanism of cerium(IV) oxidation of hexitols, i.e. D-sorbitoL and D-mannitoL, in aqueous sulfuric acid media have been studied in the presence and absence of surfactants. Under the kinetic conditions, [S] t [Ce(IV)]T , where [S]T is the total substrate (D-sorbitol or D-mannitol) concentration, the overall process shows a first-order dependence on [Ce(IV)]T and [S]T. The process is acid catalyzed and inhibited by [HSO4-]. From the [HSO4-] dependence, it has been noted that the both Ce(SO4)2+ and Ce(SO4)2 have been found kinetically active. The different rate constants in the presence and absence of surfactants have been estimated with the activation parameters. N-cetylpyridinium chloride has been found to retard the oxidation process of hexitols, whereas sodium dodecyl sulfate has been found to accelerate the rate process. All these findings including the micellar effects have been interpreted in terms of the proposed reaction mechanism and partitioning behavior of the kinetically active different species of Ce(IV) between the aqueous and pseudomicellar phase.
- Das, Asim K.,Islam, Monirul,Bayen, Ruhidas
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- Structural characterization of immunostimulating polysaccharide from cultured mycelia of Cordyceps militaris
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The water soluble crude polysaccharide obtained from cultured mycelia of Cordyceps militaris (CPM) by hot water extraction followed by ethanol precipitation was fractionated by DEAE cellulose and Sepharose CL-6B column chromatography. This fractionation process resulted in four polysaccharide fractions that were termed CPMN Fr I, CPMN Fr II, CPMN Fr III, and CPMN Fr IV. Of these fractions, CPMN Fr III was able to upregulate the functional events mediated by activated macrophages, such as production of nitric oxide (NO) and expression of cytokines (IL-1β and TNF-α). Its structural characteristics were investigated by a combination of chemical and instrumental analyses, including methylation, reductive cleavage, acetylation, Fourier transform infrared spectroscopy (FT-IR), and gas chromatography-mass spectrometry (GC-MS). Results indicate that CPMN Fr III was a high molecular mass polysaccharide with a random coil conformation of the β-1,4-branched-β-1,6-galactoglucomannan.
- Lee, Jong Seok,Kwon, Jeong Seok,Yun, Jong Seok,Pahk, Jung Woon,Shin, Won Cheol,Lee, Shin Young,Hong, Eock Kee
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- Substantial spatial flexibility and hydrogen bonding within the catalysis exerted by cyclodextrin artificial glycosidases
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Herein we report the synthesis of a novel 7A,7 D-dicyanohydrin-β-cyclodextrin that catalyzes the hydrolysis of aryl glycosides with up to 5500 times rate increase (kCat/k uncat), functioning as a glycosidase enzyme mimic. For all glycoside substrates tested at 50 mM phosphate buffer this catalysis is superior to previously reported results for 6A, 6D-dicyanohydrin cyclodextrin (CD) artificial glycosidases, i.e. analogues which have their catalytic group one carbon atom closer to the cyclodextrin cavity. This provides proof of substantial flexibility within the catalysis exerted by these CD chemzymes, A series of permethylated mono- and dicyanohydrin α- and β-CDs were also synthesized, and these showed more modest catalytic rate enhancements of up to 110 times (10% catalysis rate, relative to non-methylated analogues), implying that the permethylation blocks or hampers catalytically important binding between the saccharide part of the substrate and the CD. For comparison, the permethylated 6A,6D-dicarboxylic acid β-CD was also synthesized and afforded 25% activity (up to 250 times rate increase) relative to the nonpermethylated 6A,6D- dicarboxylic acid β-CD. This suggests that the catalytic effect of the polar interactions of the ionized carboxylate entity is less dependent on the substrate position. These findings afford new information on the scopes and boundaries for CD artificial glycosidase catalysis, and the spatial flexibility discovered fosters optimism for future advances and discoveries within the field of artificial enzymes.
- Bjerre, Jeannette,Bols, Mikael
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- One-pot conversion of cellobiose to mannose using a hybrid phosphotungstic acid-cerium oxide catalyst
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A hybrid catalyst composed of phosphotungstic acid coated cerium oxide nanoparticles was demonstrated to catalyze the one-pot conversion of cellobiose, the disaccharide unit of cellulose, to a monosaccharide mixture of glucose and mannose. A high % conversion of cellobiose (up to 99%) was achieved resulting in a yield of mannose up to 15.8%. The yield of mannose from a glucose starting material was 22.8%, exceeding those of previous cerium-based glucose epimerization catalysts. The components of the hybrid material were revealed to function synergistically via a two-step process. Cellobiose was hypothesized to be first hydrolyzed to glucose, which was subsequently epimerized to mannose by the cerium ions leached from the catalyst. The 13C NMR spectroscopic study suggested that the epimerization likely occurred by way of a 1,2-carbon shift reaction mechanism. This journal is
- Gernhart, Zane C.,Bhalkikar, Anuja,Burke, John J.,Sonnenfeld, Kate O.,Marin, Chris M.,Zbasnik, Richard,Cheung, Chin Li
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- Production of monosaccharides and bio-active compounds derived from marine polysaccharides using subcritical water hydrolysis
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Polysaccharides are the major components of brown seaweed, accounting for approximately 40-65% of the total mass. The majority of the brown seaweed polysaccharides consists of alginate (40% of dry matter), a linear hetero-polysaccharides commonly developed in fields. However, depolymerisation of alginate is required to recover high-value compounds. In this report, depolymerisation was performed using subcritical water hydrolysis (SWH) at 180-260 °C, with a ratio of material to water of 1:25 (w/v) and 1% formic acid as a catalyst. Sugar recovery was higher at low temperatures in the presence of catalyst. The antioxidant properties of Saccharina japonica showed the best activity at 180 °C in the presence of a catalyst. The mass spectra produced using MALDI-TOF showed that polysaccharides and oligosaccharides were produced during hydrothermal treatment. Hydrolysis treatment at 180 °C in the presence of a catalyst may be useful for modifying the structure of S. japonica and purified alginate.
- Meillisa, Aviannie,Woo, Hee-Chul,Chun, Byung-Soo
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- Synthesis, structure, and properties of allylamino glycosides
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Glycosylation of allylamine with D-glucose, D-galactose, and D-mannose in dry primary aliphatic alcohols was studied. The structures of the resulting N-allyl glycosylamines were established, and their reactivities were studied. It was found that N-allyl glycosylamines tend to structural isomerization involving a change in ring size and do not tend to radical polymerization in the presence of azo initiators.
- Shul'Tsev,Panarin
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- Gargantulide A, a complex 52-membered macrolactone showing antibacterial activity from streptomyces sp.
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Gargantulide A (1), an extremely complex 52-membered macrolactone, was isolated from Streptomyces sp. A42983 and displayed moderate activity against MRSA. The planar structure of 1 was determined using 2D NMR, and its stereochemistry was partially established on the basis of NOESY correlations, J-based configuration analysis, and Kishi's universal NMR database.
- Rho, Jung-Rae,Subramaniam, Gurusamy,Choi, Hyukjae,Kim, Eun-Hee,Ng, Sok Peng,Yoganathan,Ng, Siewbee,Buss, Antony D.,Butler, Mark S.,Gerwick, William H.
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- Effects of cultured Cordyceps mycelia polysaccharide A on tumor neurosis factor-α induced hepatocyte injury with mitochondrial abnormality
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Cordyceps sinensis mycelia polysaccharide A (CPS-A), was isolated from cultured Cordyceps mycelia by 65% alcohol extraction and ion-exchange column chromatography. The molecular weight of CPS-A was 1.2?×?104?Da and the backbone was mainly composed of (1?→?2)-linked β-D-mannopyranose, (1?→?2,4)-linked β-D-mannopyranose and (1?→?4)-linked α-D-glucopyranose with terminal β-D-mannopyranose and α-D-glucopyranose residues. CPS-A played a protective role against TNF-α induced mitochondria injury in L02 cells via up-regulation of mitofusin 2, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), and membrane potential. CPS-A also played a protective role against TNF-α induced L02 cells apoptosis via up-regulation of Bcl-2 and down-regulation of Bid, Bax, cleaved caspase-3, cleaved caspase-9 and ROS production. Moreover, CPS-A attenuated both the normal expression and overexpression of TNF-α receptor 1 (TNFR1) induced by TNF-α administration. In conclusion, CPS-A was involved in TNF-α induced mitochondria abnormality via TNFR1/ROS/Mfn2 pathway.
- Tang, Huiling,Wei, Weikun,Wang, Wang,Zha, Zhengqi,Li, Ting,Zhang, Zhijie,Luo, Chen,Yin, Hongping,Huang, Fengjie,Wang, Ying
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- Ligand-conjugated pH-sensitive polymeric micelles for the targeted delivery of gefitinib in lung cancers
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The aim of the present study was to investigate the tumor targeting potential of a mannose-conjugated pH-sensitive nanosystem for the effective delivery of gefitinib (Gnb) to lung cancers. We have successfully demonstrated the potential of mannose-tagged nanomicelles as an efficient vector to transport the anticancer drug. The micelles had nanosized particles with excellent dispersity index. The nanomicelles exhibited a pH-responsive nature with enhanced drug release in acidic pH conditions. Fluorescence and flow cytometer analysis showed a superior cellular uptake for the mannose-tagged nanomicelles. Confocal laser scanning microscopy study revealed a receptor-mediated cellular internalization process. The M-NP-Gnb showed a superior anticancer effect in A549 cancer cells and remarkably inhibited cancer cell proliferation. Furthermore, M-NP-Gnb significantly increased the proportion of cells in the apoptosis and necrosis region. Importantly, the half-life of Gnb encapsulated in nanomicelles increased by about 5-fold compared to that of free Gnb. The augmented half-life clearly indicates the maximum residence time of the drug in the systemic circulation. Consistently, M-NP-Gnb showed a 7-fold higher accumulation of drug in tumor tissues compared to that of free Gnb. Overall, PLGA/His-based nanomicelles could be a promising delivery system to increase the therapeutic efficiency of Gnb in lung cancers.
- Wang, Shi-Jiang,Huo, Zhi-Jun,Liu, Kai,Yu, Ning,Ma, Yan,Qin, Yue-Hong,Li, Xiao-Chen,Yu, Jin-Ming,Wang, Zhi-Qi
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- New secondary metabolites from Asphodelus tenuifolius
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Asphorins A and B (1 and 2, resp.), two new triterpene glycosides, have been isolated along with a new chromone, 3, from the AcOEt subfraction of the MeOH extract of the whole plant of Asphodelus tenuifolius. Their structures were elucidated by spectral analysis including 2D-NMR spectroscopic experiments. Copyright
- Safder, Muhammad,Mehmood, Rashad,Ali, Bakhat,Mughal, Uzma Rasheed,Malik, Abdul,Jabbar, Abdul
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- Purification, characterization and immunomodulating activity of a polysaccharide from flowers of Abelmoschus esculentus
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A water-soluble polysaccharide (OFPS11) was obtained from okra (Abelmoschus esculentus) flowers using aqueous extraction and purification with DEAE-52 cellulose and Sephacryl S-500 column. Its preliminary characterization and immunomodulating activity were investigated. Results showed that OFPS11 is mainly composed of galactose and rhamnose in a molar ratio of 2.23:1 with molecular mass of 1700 kDa. RAW264.7 cells pretreated with OFPS11 significantly inhibited the proliferation of HepG-2 cells. Additionally, OFPS11 enhanced the phagocytic ability and induced the elevation of NO production, TNF-α and IL-1β secretion of RAW264.7 cells. Furthermore, OFPS11 promoted both the expression of iNOS protein and of iNOS and TNF-α mRNA. OFPS11 can strongly increase NF-κB levels in nucleuses, which is an important transcription factor that can modulate expressions of iNOS, NO and TNF-α. These outcomes support that OFPS11 exerts its antitumor activity by probably stimulating macrophage activities through nuclear NF-κB pathway.
- Zheng, Wei,Zhao, Ting,Feng, Weiwei,Wang, Wei,Zou, Ye,Zheng, Daheng,Takase, Mohammed,Li, Qian,Wu, Huiyu,Yang, Liuqing,Wu, Xiangyang
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- Structural investigation and comparative cytotoxic activity of water-soluble polysaccharides from fruit bodies of the medicinal fungus quinine conk
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The structures and cytotoxic activities of water-soluble polysaccharides were investigated to search for biologically active polysaccharides from the fruit bodies of quinine conks (Fomitopsis officinalis). The decoctions of this medical fungus are actively used in folk medicine in many countries and traditional Chinese medicine. From the fungal extract we prepared, only branched β-glucan had cytotoxic activity among all the water-soluble polysaccharides. This glucan is characterized by a regular structure. Its backbone is formed by 1,3-linked β-D-Glcp residues, of which every third residue is substituted at O-6 by a single β-D-Glcp residue. It has a triple helix conformation according to the data obtained from a colorimetric assay with Congo red dye and is characterized by a high-weight average molar mass (Mw > 800 kDa). β-Glucan possessed cytotoxic activity against HeLa cells (IC50 = 318 ± 47 μg/mL) and induced the formation of apoptotic bodies around most cancer cells at a concentration of 200 μg/mL. It should be noted that extraction with boiling water, which is usually used to obtain extracts and decoctions, is unable to isolate active β-glucan. Active β-glucan can be obtained in an individual state by cold alkali extraction after dehydration of the fruit bodies and removal of the components extractable by boiling water.
- Golovchenko, Victoria V.,Naranmandakh, Shinen,Ganbaatar, Jamsranjav,Prilepskii, Artur Yu.,Burygin, Gennady L.,Chizhov, Alexander O.,Shashkov, Alexander S.
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- Molybdenum-based polyoxometalates as highly active and selective catalysts for the epimerization of aldoses
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In this contribution, we report on the high activity and selectivity of Keggin structure molybdenum-based polyoxometalates (POMs) in catalyzing the epimerization of aldoses. Near-equilibrium conversions and selectivities were obtained within the first hour of operation under aqueous conditions at relatively low temperatures and a wide range of pHs. Characterization of the molybdenum-based POM catalysts using X-ray diffraction and FTIR studies before and after the reaction showed no evidence of their decomposition. Our studies suggest that the active sites for the reaction are the molybdenum oxide octahedra on the surface of the Keggin structure of the molybdenum-based POMs (H3PMo12O40, Ag3PMo 12O40, Sn0.75PMo12O40). Further characterization of the system using 31P NMR and X-ray photoelectron spectroscopy experiments showed that the interaction between the aldose (e.g., glucose) and the molybdenum oxide octahedra in the POM results in electron transfer from the aldose to molybdenum, leading to the formation of the reduced form of the POM (also known as heteropoly blue). Isotope labeling experiments demonstrated that the epimerization of glucose using molybdenum-based POMs proceeds via an intramolecular C1-C2 shift mechanism with an activation barrier of as low as ～96 kJ/mol, obtained using controlled kinetic experiments. These findings open up avenues for the implementation of molybdenum-based POMs as single, selective, and stable catalytic systems for the efficient epimerization of aldoses under aqueous conditions at relatively low temperatures and a wide range of pHs.
- Ju, Feifei,Vandervelde, David,Nikolla, Eranda
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- C-2 Epimerization of Aldoses promoted by Combinations of Metals and Diamines involving a Novel Rearrangement of the Carbon Skeleton
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Aldoses are epimerized at C-2 by combinations of certain metals (Ni2+, Co2+, Ca2+, and Sr2+) and diamines (N,N,N'-trimethylethylenediamine and N,N,N',N'-tetramethylethylenediamine), and a 13C n.m.r. study reveals that a novel rearrangement of the carbon skeleton, the exchange of C-1 and C-2 atoms by inversion of the C-1-C-2 aldose fragment, is involved in this reaction.
- Tanase, Tomoaki,Shimizu, Fumihiko,Kuse, Manabu,Yano, Shigenobu,Yoshikawa, Sadao,Hidai, Masanobu
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- Structural features and anti-gastric cancer activity of polysaccharides from stem, root, leaf and flower of cultivated Dendrobium huoshanense
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The structure features and anti-gastric cancer activities in vitro of stem, root, leaf and flower polysaccharides from cultivated Dendrobium huoshanense were investigated systematically. Stem polysaccharide (cDHPS) was composed of →4)-β-D-Glcp-(1→, →4)-β-
- Liu, Bing,Shang, Zhen-Zi,Li, Qiang-Ming,Zha, Xue-Qiang,Wu, De-Ling,Yu, Nian-Jun,Han, Lan,Peng, Dai-Yin,Luo, Jian-Ping
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- A novel linear 3-O-methylated galactan isolated from Cantharellus cibarius activates macrophages
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A novel polysaccharide (WCCP-N-b) with a molecular weight of 18 kDa was isolated and purified from the fruiting bodies of Cantharellus cibarius. Monosaccharide composition, methylation analysis and NMR spectra indicated that WCCP-N-b was a linear α-1,6-galactan, partially methylated at O-3 of galactose. The molar ratio of Gal, 3-methylated-Gal, Glc and Man was 14.4:4.6:1.0:1.2. WCCP-N-b could significantly increase macrophage phagocytosis, release of NO and secretion of TNF-α, IL-6 and IL-1β. On a cellular mechanistic level, WCCP-N-b activated MAPKs and NF-κB signaling pathway via Toll-like receptor 2 (TLR2). To further elucidate the structure-function relationship, WCCP-N-b was hydrolyzed by acid. Four degraded fragments were obtained, with molecular weights of 16.1 kDa, 11.2 kDa, 5 kDa and 3.5 kDa, respectively. Their macrophage activation effects were significantly decreased along with the molecular weight decrease. Collectively, WCCP-N-b could activate RAW264.7 cells, and the activation effect was related to its molecular weight.
- Yang, Guang,Qu, Yunhe,Meng, Yue,Wang, Yushi,Song, Chengcheng,Cheng, Hairong,Li, Xiaomeng,Sun, Lin,Zhou, Yifa
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- Purification, characterization and antitumor activity of an exopolysaccharide produced by Bacillus velezensis SN-1
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A capsular polysaccharides (CPS) producer Bacillus velezensis SN-1 (B. velezensis SN-1) was isolated in Da-jiang, China. We used ultrasonic extraction to obtain CPS from a culture of B. velezensis SN-1 at a yield of 755 mg/L. Using gel permeation chromatography (GPC), CPS was separated into a single peak with a molecular weight of 1.46 × 105 Da. Its structures were characterized by gas chromatography (GC), methylation, Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR). The CPS was identified as a polysaccharide with a highly branched main chain of mannose with (1 → 3) connections. Moreover, our results revealed that CPS has the capacity to scavenge DPPH radical, hydroxyl radical, ABTS radical and oxygen radical in a manner that relied on concentration. Anti-neoplastic analysis showed that CPS displayed significant anti-tumor activity towards HepG-2 tumor cells. Above findings indicate that CPS generated by B. velezensis SN-1 may be adapted for use as a natural antioxidant in foodstuffs and as an anti-tumor drug.
- Cao, Chengxu,Li, Yang,Wang, Cong,Zhang, Naiqi,Zhu, Xinyuan,Wu, Rina,Wu, Junrui
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- Molecular Recognition Ability of a Nickel(II) Complex: Effect of Chirality of Diamine Ligand in Aldose Epimerization
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The complex composed of nickel(II) and the optically active N,N'-diethylcyclohexane-1,2-diamine (chxn) showed ability to recognize the shape of molecules in terms of the configuration of the various OH groups in aldoses during the epimerization of D-glucose to D-mannose.
- Hataya, Koji,Yanagihara, Ryoji,Osanai, Shuichi,Yoshikawa, Sadao
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- Structure and anticancer activity of native and modified polysaccharides from brown alga Dictyota dichotoma
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The laminaran DdL and fucoidan DdF were obtained from the brown alga Dictyota dichotoma. DdF was a sulfated (28.9%) and acetylated heteropolysaccharide containing fucose, galactose, mannose and glucose (57.9, 20.4, 12.4 and 9.2 mol%, respectively). DdL was a 1,3;1,6-β-D-glucan with the main chain built from 1,3-linked glucose residues and single glucose residue in branches at C6 (one branch on three glucose residues of the main chain). Sulfated (43.7%) laminaran DdLs was obtained from DdL by sulfation. It was determined that sulfates occur at C2, C4 and C6 of glucose residues. The anticancer effect of DdF, DdL, and DdLs (200 μg/mL) was studied in vitro on colon cancer cells HCT-116, HT-29, and DLD-1. The effect of polysaccharides (40 μg/mL) on colony formation of DLD-1 cancer cells after irradiation (4 Gy) was investigated first. All polysaccharides showed a synergistic effect with X-ray irradiation against cancer cells, decreasing the amount and size of cancer cells colonies.
- Usoltseva, Roza V.,Shevchenko, Natalia M.,Malyarenko, Olesya S.,Ishina, Irina A.,Ivannikova, Svetlana I.,Ermakova, Svetlana P.
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- Structural characterization of an active polysaccharide of longan and evaluation of immunological activity
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An active polysaccharide (LPD2) was isolated from longan pulp by comparing the effects of polysaccharides on the phagocytosis of macrophages. LPD2 was composed of arabinose, mannose, glucose, and galactose in a molar ratio of 0.25:0.49:1:0.5 with average molecular weight of 9.64 × 106 Da. The main linkages of the sugar residues of LPD2 were (1→4)-β-Glc and (1→6)-β-Man. LPD2 significantly enhanced the lymphocytes proliferation, phagocytosis and NO and IL-6 secretion by macrophage. The anti-TLR2 and anti-TLR4 mAbs markedly suppressed LPD2-mediated NO and IL-6 production. Furthermore, anti-TLR4 or anti-TLR2 plus anti-TLR4 treatment significantly decreased LPD2-induced increase of MyD88, IRAK4, TRAF6 and INOS mRNA expression. Moreover, western blotting analysis showed that LPD2 enhanced the expression of target proteins in MyD88/IRAK4-TRAF6- INOS pathways. These results suggested that LPD2 induced macrophage activation partly via the TLR2- and TLR4-mediated MyD88/IRAK4-TRAF6 signaling pathways. Knowing the structural features and activities of active polysaccharide of longan gives the insights into longan polysaccharide application as an immunomodulatory agent.
- Rong, Yu,Yang, Ruili,Yang, Yuzhe,Wen, Yazhou,Liu, Sixin,Li, Congfa,Hu, Zhuoyan,Cheng, Xiangrong,Li, Wu
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- Acid hydrolysis of O-acetyl-galactoglucomannan
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Acid hydrolysis of O-acetyl-galactoglucomannan (GGM), the main non-cellulosic polysaccharide in coniferous wood, was studied at 90°C in the pH range of 0.5-2.0 using different acids (hydrochloric acid, sulfuric acid, trifluoroacetic acid, oxalic acid, and formic acid) as homogeneous catalysts and cation exchange resins (Smopex 101 and Amberlyst 15) as heterogeneous catalysts. The hydrolysis rate was exclusively dependent on the pH of the solution, but independent of the concentration and type of acid. Analysis of the formation rates of oligomers with DP 2-5 revealed that GGM hydrolysis occurs rather randomly. The final products were mannose, galactose, and glucose. In the beginning of the reaction, the formation of galactose was slightly faster than those of other sugars, since galactose is a side substituent to the glucose-mannose main chain of GGM. However, with longer reaction times, the formation rates of sugar monomers were correlated with their initial abundances in the polysaccharide. Autocatalytic kinetics was observed in the presence of the heterogeneous catalysts: an induction time was observed, after which the reaction proceeded with the same rates as with homogeneous acids. The autocatalytic effect is probably explained by the increase of the hydrolysis rate constant, as the GGM chain length decreases and the molecule becomes more accessible for the active sites on the outer surface of the catalyst. The Royal Society of Chemistry 2013.
- Kusema, Bright T.,Toennov, Tea,Maeki-Arvela, Paeivi,Salmi, Tapio,Willfoer, Stefan,Holmbom, Bjarne,Murzin, Dmitry Yu.
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- Isopimarane diterpene glycosides, apoptosis inducers, obtained from fruiting bodies of the ascomycete Xylaria polymorpha
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The methanol extract of fruiting bodies of the ascomycete Xylaria polymorpha afforded three isopimarane diterpene glycosides, namely, 16-α-d-mannopyranosyloxyisopimar-7-en-19-oic acid (1), 15-hydroxy-16-α-d-mannopyranosyloxyisopimar-7-en-19-oic acid (2),
- Shiono, Yoshihito,Motoki, Sadayoshi,Koseki, Takuya,Murayama, Tetsuya,Tojima, Masato,Kimura, Ken-ichi
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- Mitochondria related pathway is essential for polysaccharides purified from Sparassis crispa mediated neuro-protection against glutamate-induced toxicity in differentiated PC12 cells
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The present study aims to explore the neuro-protective effects of purified Sparassis crispa polysaccharides against L-glutamic acid (L-Glu)-induced differentiated PC12 (DPC12) cell damages and its underlying mechanisms. The Sparassis crispa water extract was purified by a DEAE-52 cellulose anion exchange column and a Sepharose G-100 column. A fraction with a molecular weight of 75 kDa and a diameter of 88.9 nm, entitled SCWEA, was obtained. SCWEA was identified with a triple helix with (1?3)-linked Rha in the backbone, and (1?2) linkages and (1?6) linkages in the side bone. Our results indicated that the pre-treatment of DPC12 cells with SCWEA prior to L-Glu exposure effectively reversed the reduction on cell viability (by 3-(4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay) and reduced L-Glu-induced apoptosis (by Hoechst staining). SCWEA decreased the accumulation of intracellular reactive oxygen species, blocked Ca2+ influx and prevented depolarization of the mitochondrial membrane potential in DPC12 cells. Furthermore, SCWEA normalized expression of anti-apoptotic proteins in L-Glu-explored DPC12 cells. These results suggested that SCWEA protects against L-Glu-induced neuronal apoptosis in DPC12 cells and may be a promising candidate for treatment against neurodegenerative disease.
- Hu, Shuang,Wang, Di,Zhang, Junrong,Du, Mengyan,Cheng, Yingkun,Liu, Yan,Zhang, Ning,Wang, Di,Wu, Yi
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- Preparation and biological activities of an exopolysaccharide produced by Enterobacter cloacae Z0206
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A water-soluble extracellular polysaccharide (EPS-1) was isolated from the submerged culture broth of Enterobacter cloacae Z0206 through fermentation, ethanol precipitation, anion-exchange and gel-permeation chromatography. Its structural analysis showed that the average molecular weight of EPS-1 was 23,928 Da, and it was composed of glucose, mannose and galactose with a molar ratio of 6.860:1.180:0.455. It was hypothesized that EPS-1 belongs to the α-type heteropolysaccharide with pyran group. Bioactivity tests in vivo showed that the administration of EPS-1 to cyclophosphamide (CP)-exposed animals resulted in significant increase and recovery of B lymphocyte proliferation, tumor necrosis factor α (TNF-α) production and activities of antioxidant enzymes (superoxide dismutase (SOD) and glutathione peroxidase (GPx)). It is suggested that EPS-1 could provide protection against CP-induced immunosuppression and oxidative damage in mice model, and it may act as a potent immunomodulatory and antioxidant agent.
- Jin, Mingliang,Wang, Youming,Xu, Chunlan,Lu, Zeqing,Huang, Ming,Wang, Yizhen
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- Isolation and characterization of a novel polysaccharide as a possible allergen occurring in wheat flour
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A new polysaccharide with a molecular weight of 5.0 × 104 was isolated as a possible wheat allergen from a water-soluble fraction of flour by affinity chromatography and gel filtration. The isolated polysaccharide was found to be a possible wheat allergen, as it bound specifically to IgE antibodies in the sera of patients allergic to the water-soluble fraction of flour. Chemically, the sugar moiety of the polysaccharide consisted of D-glucose and D-mannose with β-1,4-linkages in a molar ratio of 4.4:1. Since this mannoglucan is thought to be stable in our body, it would act as a remaining allergen to cause a long-lasting allergic reaction to wheat flour.
- Tanabe, Soichi,Watanabe, Jun,Oyama, Kazunobu,Fukushi, Eri,Kawabata, Jun,Arai, Soichi,Nakajima, Tasuku,Watanabe, Michiko
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- Characterization and antioxidant activities of extracellular and intracellular polysaccharides from Fomitopsis pinicola
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Fomitopsis pinicola (F. pinicola) is a kind of medicinal fungi, and few studies has been carried out on F. pinicola polysaccharides from liquid submerged cultivation. The characterization and antioxidant activities of extracellular polysaccharide (EPS) and intracellular polysaccharide (IPS) isolated from F. pinicola were investigated. The results showed that the molecular weight of EPS was 2.30 × 104 Da, and EPS was composed of mannose, rhamnose, xylose and galactose with the molar ratio of 0.1:1.0:0.3:0.5. The molecular weight of IPS was 4.07 × 105 Da, and the monosaccharide compositions included glucose, mannose, rhamnose, xylose and galactose with the molar ratio of 1.0:0.9:0.9:0.8:1.1. Antioxidant activities of both EPS and IPS including in vitro scavenging activities on 1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals, cellular protective effects on yeast cells from ultraviolet (UV) radiation and H2O2 oxidative damage were tested. Both EPS and IPS showed antioxidant activities in a dose dependent manner, and IPS had higher antioxidant activity than EPS. So EPS and IPS could be potential novel antioxidants for functional food.
- Hao, Limin,Sheng, Zhicun,Lu, Jike,Tao, Ruyu,Jia, Shiru
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- Comparative study on the structural characterization and α-glucosidase inhibitory activity of polysaccharide fractions extracted from Sargassum fusiforme at different pH conditions
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Sargassum fusiforme polysaccharides (SFPs), including SFP-3-40, SFP-3-60, SFP-3-80, SFP-7-40, SFP-7-60, SFP-7-80, SFP-10-40, SFP-10-60, and SFP-10-80, were extracted at different pH (3, 7, and 10), and then precipitated with graded precipitation of 40%, 60% and 80% (v/v) ethanol solution, respectively. Their physicochemical properties and α-glucosidase inhibitory activity were determined. Results showed that SFPs significantly differed in the contents of total sugar, protein, uronic acid, sulfate, the zeta potential, and molecular weight distribution. SFPs, including SFP-10-40, SFP-10-60, and SFP-10-80, had bigger absolute zeta potential value and higher respective average molecular weight in the same ethanol concentration precipitate. All samples were mainly composed of fucose, glucuronic acid, and mannose with different molar ratios. The extraction pH and precipitation ethanol solution concentration caused little changes in functional groups, but significantly altered surface morphology of SFPs. Congo red test revealed that all polysaccharides were not helical polysaccharides. Rheological measurements indicated that SFPs were pseudoplastic fluids and showed elastic behavior of the gel. Except SFP-3-40 and SFP-3-60, all other samples had a stronger α-glucosidase inhibitory activity than that of acarbose. The inhibition type of SFPs against α-glucosidase varied owing to different extraction pH and precipitation ethyl concentration. This study shows that extraction pH can significantly affect the structure and hypoglycemic activity of SFPs and provide a data support for the scientific use of Sargassum fusiforme in industrial production.
- Jia, Rui-Bo,Li, Zhao-Rong,Lin, Lianzhu,Luo, Donghui,Ou, Zhi-Rong,Zhao, Mouming,Zheng, Qianwen
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p. 602 - 610
(2021/11/30)
-
- A novel acid polysaccharide from Boletus edulis: extraction, characteristics and antitumor activities in vitro
-
A novel cold-water-soluble polysaccharide (BEP), with a molecular weight of 6.0 × 106?Da, was isolated from Boletus edulis. BEP consists of galactose, glucose, xylose, mannose, glucuronic, and galacturonic acid in a ratio of 0.34:0.28:0.28:2.57:1.00:0.44. The IR results showed that BEP was an acid polysaccharide, containing α-type and β-type glucoside bonds. MTT assay showed BEP could inhibit cell proliferation significantly. Morphological observation demonstrated that BEP-treated MDA-MB-231 and Ca761 cells exhibited typical apoptotic morphological features. Flow cytometry analysis revealed that BEP caused mitochondrial membrane potential collapse. Annexin V-FITC/PI staining indicated that BEP induced apoptosis of MDA-MB-231 and Ca761 cells through cell block in S phase and G0/G1 phase, respectively. Western blot results showed that BEP could increase the Bax/Bcl-2 ratios, promote the release of cytochrome C, and activate the expression of caspase-3 and caspase-9 in MDA-MB-231 and Ca761 cells. In conclusion, our results demonstrated that BEP could inhibit the proliferation of breast cancer cells and induce apoptosis through mitochondrial pathways.
- Meng, Ting,Yu, Sha-sha,Ji, Hai-yu,Xu, Xiao-meng,Liu, An-jun
-
-
- Orthogonal Active-Site Labels for Mixed-Linkage endo-β-Glucanases
-
Small molecule irreversible inhibitors are valuable tools for determining catalytically important active-site residues and revealing key details of the specificity, structure, and function of glycoside hydrolases (GHs). β-glucans that contain backbone β(1,3) linkages are widespread in nature, e.g., mixed-linkage β(1,3)/β(1,4)-glucans in the cell walls of higher plants and β(1,3)glucans in yeasts and algae. Commensurate with this ubiquity, a large diversity of mixed-linkage endoglucanases (MLGases, EC 3.2.1.73) and endo-β(1,3)-glucanases (laminarinases, EC 3.2.1.39 and EC 3.2.1.6) have evolved to specifically hydrolyze these polysaccharides, respectively, in environmental niches including the human gut. To facilitate biochemical and structural analysis of these GHs, with a focus on MLGases, we present here the facile chemo-enzymatic synthesis of a library of active-site-directed enzyme inhibitors based on mixed-linkage oligosaccharide scaffolds and N-bromoacetylglycosylamine or 2-fluoro-2-deoxyglycoside warheads. The effectiveness and irreversibility of these inhibitors were tested with exemplar MLGases and an endo-β(1,3)-glucanase. Notably, determination of inhibitor-bound crystal structures of a human-gut microbial MLGase from Glycoside Hydrolase Family 16 revealed.
- Jain, Namrata,Tamura, Kazune,Déjean, Guillaume,Van Petegem, Filip,Brumer, Harry
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p. 1968 - 1984
(2021/05/26)
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- Anti-inflammatory active components of the roots of Datura metel
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One new phenolic glycoside, methyl 3,4-dihydroxyphenylacetate-4-O-[2-O-β-D-apisoyl-6-O-(2-hydroxybenzoyl)]-β-D-glucopyranoside (1), together with 10 known compounds (2–11), were isolated from the roots of Datura metel. The structures of these compounds we
- Qin, Ze,Zhang, Jin,Chen, Liang,Liu, Shu-Xiang,Zhao, Hai-Feng,Mao, Hui-Min,Zhang, Hong-Yang,Li, De-Fang
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p. 392 - 398
(2020/03/30)
-
- Promotion effect of Mg on a post-synthesized Sn-Beta zeolite for the conversion of glucose to methyl lactate
-
Mg-Sn-Beta zeolites with different Mg/Sn molar ratios were prepared from the parent deAl-Beta by a coimpregnation method. The samples were characterized by powder X-ray diffraction (XRD), N2 physisorption, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy of the -OH region and probe molecule (pyridine, CD3CN and CHCl3) adsorption. The results indicate that Mg2+ and Sn4+ can react with silanol nests and incorporate into the framework of Beta zeolite. Moreover, it is relatively facile to incorporate Sn4+ into the framework. The framework metal sites generate Lewis (L) acid sites; however, the L acid strength of the framework Mg2+ is weaker than that of framework Sn4+. A small amount of Mg2+ interacts with isolated silanols to form extraframework species. Therefore, the introduction of Mg2+ results in a significant reduction in silanol defects and an increase in L acidity/basicity of Mg-Sn-Beta. Mg-Sn-Beta with Mg/Sn molar ratio of 1 has the least silanol defects. In the conversion of glucose to methyl lactate (MLA), Mg-Beta is less active than Sn-Beta due to its weaker L acidity. The TOF value for MLA formation increased in the order of Sn-Beta 0.25Mg-Sn-Beta ≈ 4Mg-Sn-Beta 1Mg-Sn-Beta, which is closely related to the amount of silanol defects in the catalysts. A kinetic study indicates that the apparent activation energy of the retro-aldol of fructose to MLA, which is the rate-determining step of glucose conversion to MLA, decreases over Mg-Sn-Beta compared to that over Sn-Beta and thus, the formation of MLA was promoted.
- Yang, Xiaomei,Lv, Bin,Lu, Tianliang,Su, Yunlai,Zhou, Lipeng
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p. 700 - 709
(2020/02/27)
-
- Kinetics and mechanism of quinolinium dichromate mediated oxidation of sugar alcohols in Bronsted acid media
-
Bronsted acid catalyzed oxidation of certain sugar alcohols (polyols) has been studied by quinolinium dichromate (QDC) using aqueous sulfuric, perchloric, and hydrochloric acids at different temperatures. At constant acidity, reaction kinetics revealed the second-order kinetics with a first order in [Alcohol] and [QDC]. Zucker-Hammett, Bunnett, and Bunnett-Olsen criteria were used to analyze acid-dependent rate accelerations. Bunnett-Olsen plots of (log k + Hν) versus (Hν + log [H+]), and (log k) versus (Hν + log [H+]) afforded slope values (? and ?*, respectively)?>?0.47, suggesting that a water molecule acts as a prton transfer agent in the slow step of the mechanism in the oxidation of alcohols by QDC in the presence of aqueous sulfuric, perchloric, and hydrochloric acids.
- Kodali, Satish Babu,Jakku, Narendar Reddy,Kamatala, Chinna Rajanna,Yerraguntla, Rajeshwar Rao
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p. 167 - 177
(2019/12/27)
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- Method for preparing lactic acid through catalytically converting carbohydrate
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The invention relates to a method for preparing lactic acid through catalytically converting carbohydrate, and in particular, relates to a process for preparing lactic acid by catalytically convertingcarbohydrate under hydrothermal conditions. The method disclosed by the invention is characterized by specifically comprising the following steps: 1) adding carbohydrate and a catalyst into a closedhigh-pressure reaction kettle, and then adding pure water for mixing; 2) introducing nitrogen into the high-pressure reaction kettle to discharge air, introducing nitrogen of 2 MPa, stirring and heating to 160-300 DEG C, and carrying out reaction for 10-120 minutes; 3) putting the high-pressure reaction kettle in an ice-water bath, and cooling to room temperature; and 4) filtering the solution through a microporous filtering membrane to obtain the target product. The method can realize high conversion rate of carbohydrate and high yield of lactic acid, and has the advantages of less catalyst consumption, good circularity, small corrosion to reaction equipment and the like.
- -
-
Paragraph 0029-0040
(2020/11/01)
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- Production of lactic acid derivatives from sugars over post-synthesized Sn-Beta zeolite promoted by WO3
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Various metal oxides were used as co-catalysts to improve the production of alkyl lactate over Sn-Beta-P. WO3 exhibited the best promotion effect. The yield of MLA increased from 25% (6.5 g L?1) over Sn-Beta-P (0.2 g) to 52% (13.4 g L?1) over WO3 (0.1 g) and Sn-Beta-P (0.1 g) at 160 °C for 5 h and 3.1 wt% of glucose concentration. MLA yield of 38% was attained even at glucose concentration of 10 wt% and the space-time yield reached 7.1 g L?1 h?1. The action mechanism of WO3 was investigated. Fine WO3 particles adsorbed on surface of Sn-Beta-P in reaction media and decreased the silanol defects of Sn-Beta-P. This promotes retro-aldol of fructose, the rate-determining step of whole reaction, thus facilitated the formation of MLA. Kinetic studies indicate that the presence of WO3 decreased the activation energy of the retro-aldol of fructose. The binary solid WO3 and Sn-Beta-P is recyclable.
- Yang, Xiaomei,Zhang, Yali,Zhou, Lipeng,Gao, Beibei,Lu, Tianliang,Su, Yunlai,Xu, Jie
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p. 285 - 291
(2019/03/21)
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- Polyoxomolybdates catalysed cascade conversions of cellulose to glycolic acid with molecular oxygen via selective aldohexoses pathways (an epimerization and a [2+4] Retro-aldol reaction)
-
Selective cascade conversion of cellulose into valuable C2 or C4 products over acid catalysts is still not fully explored because glucose-fructose isomerization followed by fructose conversions is thermodynamically easy to occur during the reaction, leading the formation of C6, C5, C3 and C1 products such as 5-hydroxymethylfurfural (HMF), levulinates, lactates, formates, and so on. In this study, phosphomolybdates (PMo) with the Keggin structure was found to promote cascade oxidation of cellulose conversion via selective aldohexoses pathways, i.e. an epimerization and a [2 + 4] retro-aldol of glucose/mannose, rather than aldo-ketohexoses routes, i.e. a glucose-fructose isomerization and a [3 + 3] retro-aldol of fructose, which produced glycolic acid (GlycA) (C2) as the main product (～50% selectivity). Either in aerobic or anaerobic state, PMo selectively catalyzed glucose epimerization into mannose at 100 °C. This behavior is completely different from that of molybdate in MoO3 which is only effective for the epimerization reaction (the Bilik reaction). In this cascade oxidation reaction, PMo was reduced into heteropoly-blue (PMored) as observed by the color change of the solution, UV-VIS and FT-IR measurements. In this case, the molecular oxygen was found to reoxidize PMored into PMo, leading the catalytic activity to be remained stable. The results shown in this study provide an insight for the catalyst development on selective synthesis of C2, C4 and/or other novel valuable chemicals from carbohydrates via the aldohexose pathways.
- Bayu, Asep,Karnjanakom, Surachai,Yoshida, Akihiro,Kusakabe, Katsuki,Abudula, Abuliti,Guan, Guoqing
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- Tin Grafted on Modified Alumina-Catalyzed Isomerisation of Glucose to Fructose
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The present study focuses on designing a catalyst based on hot water treated alumina (Al2O3-HWT) for the conversion of glucose to fructose. The glucose isomerisation reactions are performed with tin incorporated on parent Al2O3 and Al2O3-HWT in methanol. 0.5 wt% Sn/Al2O3-HWT affords a combined yield of fructose and methylfructoside (30.4%) which is two-fold higher than that obtained with 0.5wt% Sn/Al2O3 (15.1%), implying the importance of hot water treatment of Al2O3. Al2O3-HWT shows a very broad peak centred around 3440 cm-1, which could be assigned to OH stretching band of gibbsite, γ-Al(OH)3 which significantly diminished after solid state ion-exchange with SnCl4.5H2O (0.5 wt% Sn/Al2O3-HWT). UV-Vis diffused reflectance spectrum of 0.5 wt% Sn/Al2O3-HWT displays a peak centered at 241 nm, which can be ascribed to the incorporation of tin into the alumina network. XRD patterns of 0.5, 3 and 5 wt% Sn/Al2O3-HWT show that no peak corresponding to SnO2 is formed. Importantly, 0.5wt% SnO2/Al2O3-HWT exhibits a low activity, giving 13.2% of the total yield of fructose and methylfructoside, respectively, compared to 0.5wt% Sn/Al2O3-HWT (30.4% fructose), signifying the role of incorporated tin into the alumina network.
- Yatoo, Muhamad Aadil,Saravanamurugan, Shunmugavel
-
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- Structural elucidation, antioxidant and immunomodulatory activities of a novel heteropolysaccharide from cultured Paecilomyces cicadae (Miquel.) Samson
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The fine structure and chain conformation of a heteropolysaccharide (PCIPS3) from mycelium of Paecilomyces cicadae were investigated via the analysis of HPLC, IR, methylation, NMR spectroscopy and multiangle light scattering. It was determined to be a 2.23 × 104 g/mol heteropolysaccharide primarily composed of glucose, galactose and mannose in a molar ratio of 23.8:2.1:1.0. The PCIPS3 backbone consisted of 1,4-linked α-D-Glcp and 1,4-linked 6-O-Me-α-D-Glcp residues, which were occasionally interrupted by branched β-Galf residues through 1,6-linkage. Moreover, the α (0.60) from Mark–Houwink–Sakurada (MHS) equation suggested that PCIPS3 adopted a flexible chain conformation in 0.1 mol/L NaNO3 at 25 °C. The worm-like chains model parameters for PCIPS3 were estimated as following: ML = 437 nm?1, q = 0.46 nm and 0.79 nm, which were further evidenced by AFM. Furthermore, PCIPS3 showed excellent scavenging capacities of 2,2-diphenyl-1-picrylhydrazyl radical, superoxide radical, hydroxyl radical, ORAC radical and moderate immunomodulatory activity.
- Wang, Yanbin,He, Pengfei,He, Liang,Huang, Qingrong,Cheng, Junwen,Li, Weiqi,Liu, Yu,Wei, Chaoyang
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p. 270 - 281
(2019/04/17)
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- PROCESS FOR THE PRODUCTION OF GLYCOLS
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The invention provides a process for the preparation of glycols from a saccharide-containing feedstock in a reactor system, said process comprising: i) providing a first feed stream comprising said saccharide-containing feedstock in a first solvent at a temperature of no more than 160°C; ii) providing a second feed stream comprising a tungsten- based retro-aldol catalytic species and an alkali metal containing species in a second solvent at a temperature in the range of from 150 to 250°C; iii) combining the first feed stream and the second feed stream, before they are provided to the reactor system, to form a combined feed stream; iv) providing the combined feed stream to the reactor system and operating the reactor at a temperature in the range of from 150°C to 250°C; and v) also contacting the combined feed stream with a hydrogenation catalytic species in the presence of hydrogen, wherein the molar ratio of alkali metal:tungsten in the combined feed stream is in the range of from 0.55 to 6.
- -
-
Page/Page column 19-20
(2018/03/28)
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- Successive C1-C2 bond cleavage: The mechanism of vanadium(v)-catalyzed aerobic oxidation of d-glucose to formic acid in aqueous solution
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Vanadium(v)-catalyzed aerobic oxidation in aqueous solution shows high selectivity in the field of C-C bond cleavage of carbohydrates for chemicals with less carbon atoms. However, the pathway of C-C bond cleavage from carbohydrates and the conversion mechanism are unclear. In this work, we studied the pathway and the mechanism of d-glucose oxidation to formic acid (FA) in NaVO3-H2SO4 aqueous solution using isotope-labeled glucoses as substrates. d-Glucose is first transformed to FA and d-arabinose via C1-C2 bond cleavage. d-Arabinose undergoes similar C1-C2 bond cleavage to form FA and the corresponding d-erythrose, which can be further degraded by C1-C2 bond cleavage. Dimerization and aldol condensation between carbohydrates can also proceed to make the reaction a much more complicated mixture. However, the fundamental reaction, C1-C2 bond cleavage, can drive all the intermediates to form the common product FA. Based on the detected intermediates, isotope-labelling experiments, the kinetic isotope effect study and kinetic analysis, this mechanism is proposed. d-Glucose first reacts with a vanadium(v) species to form a five-membered-ring complex. Then, electron transfer occurs and the C1-C2 bond weakens, followed by C1-C2 bond cleavage (with no C-H bond cleavage), to generate the H3COO-vanadium(iv) complex and d-arabinose. FA is generated from H3COO that is oxidized by another vanadium(v) species. The reduced vanadium species is oxidized by O2 to regenerate to its oxidation state. This finding will provide a deeper insight into the process of C-C bond cleavage of carbohydrates for chemical synthesis and provide guidance for screening and synthesizing new highly-efficient catalyst systems for FA production.
- Niu, Muge,Hou, Yucui,Wu, Weize,Ren, Shuhang,Yang, Ru
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p. 17942 - 17951
(2018/07/14)
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- Converting galactose into the rare sugar talose with cellobiose 2-epimerase as biocatalyst
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Cellobiose 2-epimerase from Rhodothermus marinus (RmCE) reversibly converts a glucose residue to a mannose residue at the reducing end of β-1,4-linked oligosaccharides. In this study, the monosaccharide specificity of RmCE has been mapped and the synthesis of D-talose from D-galactose was discovered, a reaction not yet known to occur in nature. Moreover, the conversion is industrially relevant, as talose and its derivatives have been reported to possess important antimicrobial and anti-inflammatory properties. As the enzyme also catalyzes the keto-aldo isomerization of galactose to tagatose as a minor side reaction, the purity of talose was found to decrease over time. After process optimization, 23 g/L of talose could be obtained with a product purity of 86% and a yield of 8.5% (starting from 4 g (24 mmol) of galactose). However, higher purities and concentrations can be reached by decreasing and increasing the reaction time, respectively. In addition, two engineering attempts have also been performed. First, a mutant library of RmCE was created to try and increase the activity on monosaccharide substrates. Next, two residues from RmCE were introduced in the cellobiose 2-epimerase from Caldicellulosiruptor saccharolyticus (CsCE) (S99M/Q371F), increasing the kcat twofold.
- Van Overtveldt, Stevie,Gevaert, Ophelia,Cherlet, Martijn,Beerens, Koen,Desmet, Tom
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- Selective Glucose-to-Fructose Isomerization over Modified Zirconium UiO-66 in Alcohol Media
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Modulated zirconium metal–organic framework UiO-66 is shown to catalyze the isomerization of d-glucose to d-fructose in alcohol media. Fructose selectivity can change depending on solvent choice. We hypothesize that the difference in selectivity is related to a combined effect of adsorption and solvation effects, which may lead to the high formation of alkylglucosides in depletion of fructose if methanol or ethanol are used. A fructose selectivity of 72 % at 82 % glucose conversion in 1-PrOH was achieved. The reaction mechanism was investigated using nuclear magnetic resonance spectroscopy. We demonstrate that UiO-66 isomerizes glucose to fructose through an intramolecular C2–C1 hydride transfer. In addition, we show that modulated UiO-66 is a highly active and stable catalyst at the reaction conditions, showing great potential for other sugar reactions.
- de Mello, Matheus Dorneles,Tsapatsis, Michael
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p. 2417 - 2423
(2018/06/14)
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- Zeolitic Materials Including Paired Lewis Acid Catalytic Sites
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Disclosed are zeolitic materials that include a microporous crystalline framework substituted with one or more paired Lewis acid sites. Each of the one or more paired Lewis acid sites within the zeolitic material can comprise a first Lewis acid metal center and a second Lewis acid metal center. The first Lewis acid metal center and the second Lewis acid metal center can be separated by three or fewer atoms within the crystalline framework. Also provided herein are methods of making these zeolitic materials as well as methods of using these zeolitic materials as catalysts.
- -
-
Paragraph 0045; 0124
(2018/05/26)
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- Scope and limitations of carbohydrate hydrolysis for de novo glycan sequencing using a hydrogen peroxide/metallopeptide-based glycosidase mimetic
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Acidic hydrolysis is commonly used as a first step to break down oligo- and polysaccharides into monosaccharide units for structural analysis. While easy to set up and amenable to mass spectrometry detection, acid hydrolysis is not without its drawbacks. For example, ring-destruction side reactions and degradation products, along with difficulties in optimizing conditions from analyte to analyte, greatly limits its broad utility. Herein we report studies on a hydrogen peroxide/CuGGH metallopeptide-based glycosidase mimetic design for a more efficient and controllable carbohydrate hydrolysis. A library of methyl glycosides consisting of ten common monosaccharide substrates, along with oligosaccharide substrates, was screened with the artificial glycosidase for hydrolytic activity in a high-throughput format with a robotic liquid handling system. The artificial glycosidase was found to be active towards most screened linkages, including alpha- and beta-anomers, thus serving as a potential alternative method for traditional acidic hydrolysis approaches of oligosaccharides.
- Peng, Tianyuan,Wooke, Zachary,Pohl, Nicola L.B.
-
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- Escherichia coli O106, a new member of a group of enteric bacteria sharing an O-polysaccharide backbone structure
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O-Polysaccharides (O-antigens) of a number of genetically related Escherichia coli O-serogroups (O17, O44, O73, O77, and O106) and Salmonella enterica O:6,14 possess an identical main chain composed of d-GlcNAc and d-Man residues and differ from each other by the absence or presence of glucose side chains at various positions. Using two-dimensional NMR spectroscopy, we established the structure of the O-polysaccharide of E. coli O106 having two glucose side chains in a hexasaccharide repeating unit.
- Shashkov,Senchenkova,Naumenko,Kalinchuk,Perepelov,Knirel, Yu. A.
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p. 1538 - 1541
(2018/10/31)
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- Chemical characterization and antioxidant activities of polysaccharides isolated from the stems of Parthenocissus tricuspidata
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Four polysaccharides, PTP–1, PTP–2, PTP–3 and PTP–4, were obtained from the water extraction of the stems of P. tricuspidata by anion exchange chromatography and gel filtration. The antioxidant activities of four PTPs were investigated, exhibiting different antioxidant activities, in which PTP?4 performed noticeable, with strong superoxide radical activity (comparable to BHT), high DPPH radical activity (78.53% at 1250 μg/mL), moderate hydroxyl radical scavenging activity and reducing power activity. Furthermore, the chemical structure of PTP?4 was measured by FT-IR, GC, 1H and 13C NMR spectra, indicating its mainly composition of the arabinose, xylose, galactose, glucuronic acid, and mannose. Thus, the stems of P. tricuspidata could be used as a potential source for natural antioxidant.
- Liang, Xiaoxia,Gao, Yingying,Fei, Wenbo,Zou, Yuanfeng,He, Min,Yin, Lizi,Yuan, Zhixiang,Yin, Zhongqiong,Zhang, Wei
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- Structure characterization of the mannofucogalactan isolated from fruit bodies of Quinine conk Fomitopsis officinalis
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The mannofucogalactan as a major component of water extract was obtained from fruit bodies of Fomitopsis officinalis by extraction with boiling water followed by deproteination, decoloration, and purification using anion-exchange chromatography and size exclusion chromatography. Its structure was characterized using the data of monosaccharide composition, methylation analysis, one- and two-dimensional NMR spectroscopy. The studied polysaccharide was a branched mannofucogalactan with a backbone composed of partially 3-O-methylated 1,6-O-linked α-D-galactopyranosyl residues. Almost every second residue in the backbone was substituted at O-2 by 3-O-α-D-mannopyranosyl-α-L-fucopyranosyl and β-D-galactopyranosyl residues. The non-reducing terminal α-L-fucopyranosyl units, which were identified by GC–MS analyses, appeared to be the part of mannofucogalactan side chains also.
- Golovchenko, Victoria V.,Khramova, Daria S.,Shinen, Naranmandakh,Jamsranjav, Ganbaatar,Chizhov, Alexander O.,Shashkov, Alexander S.
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p. 161 - 169
(2018/07/24)
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- Isolation, purification, characterization and antioxidant activity of polysaccharides from the stem barks of Acanthopanax leucorrhizus
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A novel water-soluble polysaccharide (named ALP-1) was successfully isolated from the stem barks of Acanthopanax leucorrhizus by hot-water extraction, and further purified by Cellulose DEAE-52 and Sephadex G-100 chromatography. The structure of ALP-1 was characterized by HPLC, HPGPC, partial acid hydrolysis, periodate oxidation, Smith degradation, methylation, together with UV, IR and NMR spectral analysis. The antioxidant activities also were evaluated in vitro. Structural analysis revealed that ALP-1 was a homogeneous galactan with the average molecular weight of 169 kDa, composed of galactose, glucose, mannose and arabinose in a molar ratio of 6.1:2.1:1.1:1.0, owning a backbone structure of 1,6-linked α-D-Galp residues with some branches of α-D-Manp-(1 → 3)-α-L-Araf residues at O-3 and α-D-Galp residues at O-4 of 1,6-linked α-D-Galp. Antioxidant assay showed that ALP-1 exhibited strong DPPH[rad] and HO[rad] scavenging activities, as well as ferric-reducing antioxidant power. These results provide a scientific basis for the further use of polysaccharides from A. leucorrhizus.
- Hu, Hao-Bin,Liang, Hai-Peng,Li, Hai-Ming,Yuan, Run-Nan,Sun, Jiao,Zhang, La-La,Han, Ming-Hu,Wu, Yun
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p. 359 - 367
(2018/05/29)
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- Optimization of ultrasound-assisted extraction of okra (Abelmoschus esculentus (L.) Moench) polysaccharides based on response surface methodology and antioxidant activity
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This study determined the optimal conditions for ultrasound-assisted extraction of a water-soluble polysaccharide, Raw Okra Polysaccharide, from the fruit of okra using response surface methodology. The optimal extraction temperature, extraction time and ultrasonic power were 59 °C, 30 min and 522 W, respectively, giving a yield of 10.35 ± 0.11%. ROP was further isolated, lyophilized and purified using a DEAE-Sepharose Fast Flow column and Sepharose CL-6B column, revealing three elution peaks subsequently designated ROP ?1, ?2, and ?3, respectively. Of these, ROP-2 showed the highest yield, and was therefore selected for physicochemical analysis and evaluation of antioxidant activity. Gas chromatography, fourier transform infrared spectroscopy, and high-performance liquid chromatography were used to characterize the primary structural features and molecular weight, revealing that ROP-2 is composed of glucose, mannose, galactose, arabinose, xylose, fructose, and rhamnose (molar percentages: 28.8, 12.5, 13.1, 15.9, 9.2, 13.7, and 6.8%, respectively) and has an average molecular weight of 1.92 × 105 Da. A superoxide radical scavenging assay and DPPH radical scavenging assay further revealed the significant in vitro antioxidant activity of ROP-2. These findings present an effective technique for extraction of the natural antioxidant ROP-2, warranting further analysis of its potential application in the food industry.
- Wang, Kunli,Li, Mo,Wen, Xin,Chen, Xiaosong,He, Zhengyu,Ni, Yuanying
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p. 1056 - 1063
(2018/04/12)
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- Formation of Chiral Structures in Photoinitiated Formose Reaction
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The possibility to synthesize biologically important sugars and other chiral compounds without any initiators in the UV-initiated reaction of formaldehyde in aqueous solution has been shown for the first time. An optically active condensed phase due to an
- Stovbun,Skoblin,Zanin,Tverdislov,Taran,Parmon
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p. 108 - 116
(2018/04/05)
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- Glucose Isomerization Using Alkali Metal and Alkaline Earth Metal Titanates
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Glucose isomerization was performed using various titanate catalysts, which include SrTiO3, BaTiO3, CaTiO3, Na2Ti6O13, K2Ti6O13, and Sr3Ti2O7, prepared using a conventional solid-phase method. Among the titanates, SrTiO3, CaTiO3, and Na2Ti6O13 offered a relatively high fructose yield (32 %) with a high selectivity (68–78 %). The yields are comparable to yields reported previously using a Sn-modified BEA zeolite, which shows a high efficiency for glucose isomerization as a Lewis acid catalyst. A study of the mechanism of glucose isomerization on a SrTiO3 catalyst surface by using 1H NMR spectroscopy suggested that the titanates catalyze the isomerization as base catalysts. Thus, the effect of the basicity of the titanates on glucose isomerization was investigated in terms of the base quantity and strength. The analysis was performed by using an acid–base titration method and FTIR spectroscopy with CHCl3 as a probe molecule. It is proposed that glucose isomerization on the titanates depends not only on the base amount but also on the base strength.
- Ohyama, Junya,Zhang, Yutong,Ito, Jun,Satsuma, Atsushi
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p. 2864 - 2868
(2017/07/28)
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- Structural diversity of Burkholderia pseudomallei lipopolysaccharides affects innate immune signaling
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Burkholderia pseudomallei (Bp) causes the disease melioidosis. The main cause of mortality in this disease is septic shock triggered by the host responding to lipopolysaccharide (LPS) components of the Gram-negative outer membrane. Bp LPS is thought to be a weak inducer of the host immune system. LPS from several strains of Bp were purified and their ability to induce the inflammatory mediators TNF-α and iNOS in murine macrophages at low concentrations was investigated. Innate and adaptive immunity qPCR arrays were used to profile expression patterns of 84 gene targets in response to the different LPS types. Additional qPCR validation confirmed large differences in macrophage response. LPS from a high-virulence serotype B strain 576a and a virulent rough central nervous system tropic strain MSHR435 greatly induced the innate immune response indicating that the immunopathogenesis of these strains is different than in infections with strains similar to the prototype strain 1026b. The accumulation of autophagic vesicles was also increased in macrophages challenged with highly immunogenic Bp LPS. Gene induction and concomitant cytokine secretion profiles of human PBMCs in response to the various LPS were also investigated. MALDI-TOF/TOF was used to probe the lipid A portions of the LPS, indicating substantial structural differences that likely play a role in host response to LPS. These findings add to the evolving knowledge of host-response to bacterial LPS, which can be used to better understand septic shock in melioidosis patients and in the rational design of vaccines.
- Norris, Michael H.,Schweizer, Herbert P.,Tuanyok, Apichai
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- Cytotoxic trichothecene-type sesquiterpenes from the sponge-derived fungus: Stachybotrys chartarum with tyrosine kinase inhibition
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Bioassay-guided fractionation of the sponge (Niphates recondite)-associated fungus Stachybotrys chartarum revealed that the EtOAc fraction shows inhibitory effects against tumor cell lines. Chromatographic separation of the active fraction resulted in the isolation of 15 trichothecene-based sesquiterpenes, including four new compounds, namely chartarenes A-D (1-4). The structures of the new compounds were determined on the basis of extensive spectroscopic analysis and chemical conversion. Compounds 1-15 exerted potent or selective inhibition against a panel of tumor cell lines including HCT-116, HepG2, BGC-823, NCI-H1650, and A2780, with IC50 values ranging from 10-2 to 10 μM. In addition, these compounds showed potent inhibition against tumor-related kinases FGFR3, IGF1R, PDGFRb, and TRKB.
- Li, Yong,Liu, Dong,Cheng, Zhongbin,Proksch, Peter,Lin, Wenhan
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p. 7259 - 7267
(2017/02/05)
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- Purification, characterization, and bioactivities of a polysaccharide from mycelial fermentation of Bjerkandera fumosa
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In this work, a novel polysaccharide (named DBFM3) was isolated from mycelia of Bjerkandera fumosa by DEAE-32 and Sepharose CL–6?B column chromatography. High-performance gel permeation chromatography showed that DBFM3 was homogeneous, with an average molecular weight of 1.8?×?105?Da. Structural characteristics of the purified fraction were investigated by high-performance liquid chromatography (HPLC), FT-IR, and NMR. HPLC analysis indicated that DBFM3 was composed of mannose, galacturonic acid, and galactose at molar ratios of 1:18.16:0.702. Spectral analysis suggested that DBFM3 had (1?→?6), (1?→?3,6), (1?→?3) linkages and pyranose conformation. Antioxidant assay in vitro showed that DBFM3 exhibited 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radical scavenging activity, and has protective effect against DNA damage and damage to SH-SY5Y cells induced by H2O2. Immunological tests indicated that DBFM3 significantly increased lymphocyte proliferation in vitro. Furthermore, DBFM3 increased the proliferation of lymphocytes in the presence of concanavalin A or lipopolysaccharide as mitogen.
- Liu, Di,Sun, Qianwen,Xu, Jing,Li, Na,Lin, Jianan,Chen, Shan,Li, Fan
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p. 115 - 122
(2017/03/23)
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- Isomerization of glucose into fructose by environmentally friendly Fe/β zeolite catalysts
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Herein, the environmentally friendly Fe/β zeolite for glucose isomerization to fructose in aqueous media was reported for the first time. The effects of various reaction conditions including reaction temperature, reaction time, catalyst dosage, etc. on the isomerization reaction over Fe/β zeolite were studied in detail. Under the optimized conditions, yield of fructose higher than 20% were obtained. Moreover, the Fe/β zeolite catalysts were stable and remained constant catalytic activity after five consecutive runs. The possible active Fe species for isomerization of glucose in Fe/β zeolite is also discussed.
- Xu, Siquan,Zhang, Lei,Xiao, Kehao,Xia, Haian
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supporting information
p. 48 - 51
(2017/05/16)
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- Isomerization of glucose to fructose catalyzed by lithium bromide in water
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This study demonstrated that glucose could be isomerized to fructose in the concentrated aqueous solution of lithium bromide (LiBr) under mild conditions. The isomerization mechanisms were studied via isotopic labeling experiments. It was found that both the cation (Li+) and the anion (Br-) in the system catalyzed the isomerization of glucose to fructose. Br- catalyzed the isomerization through the proton transfer mechanism via an enediol intermediate, while Li+ did it through an intramolecular hydride shift mechanism from C2 to C1. The estimation using quantitative 13C-NMR analysis indicated that Br- catalyzed approximately 85% of the isomerization, while Li+ was responsible for the remaining 15%. The results indicated that 31% of the fructose was produced from glucose in LiBr trihydrate at 120 °C for 15 min. The outcomes of this study provided not only a better understanding of and insights into the sugar transformations in the LiBr solution but also an alternative approach to produce fructose from glucose.
- Yoo, Chang Geun,Li, Ning,Swannell, Melanie,Pan, Xuejun
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p. 4402 - 4411
(2017/09/29)
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- Catalyst and Process Design for the Continuous Manufacture of Rare Sugar Alcohols by Epimerization–Hydrogenation of Aldoses
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Sugar alcohols are applied in the food, pharmaceutical, polymer, and fuel industries and are commonly obtained by reduction of the corresponding saccharides. In view of the rarity of some sugar substrates, epimerization of a readily available monosaccharide has been proposed as a solution, but an efficient catalytic system has not yet been identified. Herein, a molybdenum heteropolyacid-based catalyst is developed to transform glucose, arabinose, and xylose into less-abundant mannose, ribose, and lyxose, respectively. Adsorption of molybdic acid onto activated carbon followed by ion exchange to the cesium form limits leaching of the active phase, which greatly improves the catalyst stability over 24 h on stream. The hydrogenation of mixtures of epimers is studied over ruthenium catalysts, and it is found that the precursor to the desired polyol is advantageously converted with faster kinetics. This is explained by density functional theory on the basis of its more favorable adsorption on the metal surface and the lower energy barrier for the addition of a hydrogen atom to the primary carbon atom. Finally, different designs for a continuous process for the conversion of glucose into mannitol are studied, and it is uncovered that two reactors in series with one containing the epimerization catalyst and the other containing a mixture of the epimerization and hydrogenation catalysts increases the mannitol/sorbitol ratio to 1.5 from 1 for a single mixed-bed reactor. This opens a prospective route to the efficient valorization of renewables to added-value chemicals.
- Lari, Giacomo M.,Gr?ninger, Olivier G.,Li, Qiang,Mondelli, Cecilia,López, Núria,Pérez-Ramírez, Javier
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p. 3407 - 3418
(2016/12/27)
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- Modified iRNA agents
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The present invention provides effective motifs for RNA agents conjugated to at least one ligand, which are advantageous for the in vivo delivery of iRNA duplex agents. Additionally, the present invention provides methods of making these compositions, as well as methods of introducing these iRNA duplex agents into cells using these compositions, e.g., for the treatment of various disease conditions.
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- Acidic Ultrafine Tungsten Oxide Molecular Wires for Cellulosic Biomass Conversion
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The application of nanocatalysis based on metal oxides for biomass conversion is of considerable interest in fundamental research and practical applications. New acidic transition-metal oxide molecular wires were synthesized for the conversion of cellulos
- Zhang, Zhenxin,Sadakane, Masahiro,Hiyoshi, Norihito,Yoshida, Akihiro,Hara, Michikazu,Ueda, Wataru
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supporting information
p. 10234 - 10238
(2016/08/24)
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- Enhancing tungsten oxide/SBA-15 catalysts for hydrolysis of cellobiose through doping ZrO2
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The number of strong acid sites on a hydrolysis catalyst accessible by the bulky cellulose limits its efficiency in the conversion and utilization of biomass-based resources. In this work, high surface area WZr/SBA-15 catalysts (>400?m2/g) were prepared by hydrothermal method and characterized using XRD, N2 adsorption, TEM, Raman, UV–vis, XPS and FTIR of pyridine adsorption. The results showed that doping a moderate amount of ZrO2 into the WO3/SBA-15 catalyst stabilized the tungstate species in the form of a polytungstate species as a result of the strong ZrOx-WOx interaction as well as increased the surface area of the catalyst. The resulting polytungstate species provided strong Br?nsted acid sites for hydrolysis. Consequently, the cellobiose conversion was maximized at 5% ZrO2 loading, corresponding to a maximized surface area and density of Br?nsted acid sites. This catalytic activity is significantly higher than that of a WO3/ZrO2 catalyst prepared using the conventional impregnation method, indicating the importance of mesoporous structure to the dispersion of active species and to the accessibility of the active sites by the bulky reactant. This result indicates that the density of the strong Br?nsted acid sites with improved accessibility by the bulky reactant is essential to achieve a high hydrolysis activity.
- Wang, Hua,Guo, Yingge,Chang, Cuirong,Zhu, Xinli,Liu, Xiao,Han, Jinyu,Ge, Qingfeng
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p. 182 - 192
(2016/07/06)
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- Molecular structure, chemical properties and biological activities of Pinto bean pod polysaccharide
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Pinto bean pod polysaccharide (PBPP) was successfully extracted with yield of 38.5 g/100 g and the PBPP gave total carbohydrate and uronic acid contents of 286.2 mg maltose equivalent/g and 374.3 mg Gal/g, respectively. The Mw of PBPP was 270.6 kDa with intrinsic viscosity of 0.262 dm3/g, which composed of mannose (2.5%), galacturonic acid (15.0%), rhamnose (4.0%), glucose (9.0%), galactose (62.2%), xylose (2.9%) and arabinose (4.3%) with trace amount of ribose and fucose. The result suggested that PBPP has a spherical conformation with a highly branched structure. Fourier Transform Infrared analysis showed that PBPP has a similar structure as commercial pectin with an esterification degree of 59.9%, whereas scanning electron microscopy study showed that the crude polysaccharide formed a thin layer of film that was made of multiple micro strands of fibre. PBPP exhibited substantial free radical scavenging activity (7.7%), metal reducing capability (2.04 mmol/dm3) and α-amylase inhibitory activity (97.6%) at a total amount of 1 mg. PBPP also exhibited high water- and oil-holding capacities (3.6 g/g and 2.8 g/g, respectively). At a low concentration, PBPP exhibited emulsifying activity of 39.6% with stability of 38.6%. Apart from that, PBPP was able to show thickening capability at low concentration (0.005 kg/dm3).
- Kamarudin, Fazlina,Gan, Chee-Yuen
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p. 280 - 287
(2016/04/19)
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- Glucose to Fructose Isomerization in Aqueous Media over Homogeneous and Heterogeneous Catalysts
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Isomerization of glucose to fructose is an important reaction with numerous applications in terms of biomass valorization. The reaction is catalyzed enzymatically but may also proceed under alkaline conditions, in which case it is accompanied by low selectivity and formation of byproducts. Solid Lewis acid and basic catalytic materials are being studied as alternative catalysts. In this work, the isomerization of glucose to fructose in aqueous media over homogeneous and heterogeneous catalysts has been investigated. The effect of polar aprotic solvents and their mixtures with water on glucose conversion and fructose selectivity was also studied. Sodium aluminate (NaAlO2) has been proven to be very effective, resulting in high fructose yield (52.1 %) and high selectivity (84.8 %). Among the various solid catalysts tested, MgO afforded glucose conversion of 44 %, with 75.8 % and 33.4 % fructose selectivity and yield, respectively, when the isomerization reaction was conducted in neat H2O.
- Marianou, Asimina A.,Michailof, Chrysoula M.,Pineda, Antonio,Iliopoulou, Eleni F.,Triantafyllidis, Kostas S.,Lappas, Angelos A.
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p. 1100 - 1110
(2016/04/05)
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- Structural properties of polysaccharides from cultivated fruit bodies and mycelium of Cordyceps militaris
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The structural properties of polysaccharides, respectively, obtained from the fermented mycelium and cultivated fruiting bodies of the Cordyceps militaris were investigated and compared in this paper. First, the crude polysaccharides were extracted from the mycelium and the fruiting bodies, respectively. The polysaccharides were successively purified by Sevag and chromatography on Sephadex G-100 column to produce two polysaccharides fractions termed CMPS-II and CBPS-II, respectively. The average molecular weights of CMPS-II and CBPS-II were 1.402 × 103 kDa and 1.273 × 103 kDa, respectively, and they were mainly composed of mannose, glucose and galactose in the mole ratios of 1:28.63:1.41 and 1:12.41:0.74, respectively, for CMPS-II and CBPS-II. Afterward, the structural features of CMPS-II and CBPS-II were investigated by a combination of chemical and instrumental analysis, such as FT-IR, periodate oxidation-Smith degradation, GC-MS, NMR and methylation analysis. The results indicated that structurally, both CMPS-II and CBPS-II were 1,3-branched-galactomannoglucan that had a linear backbone of (1 → 4)-linked α-d-glucopyranose (Glcp). Congo-red test revealed that CMPS-II and CBPS-II existed as triple-helical chains in 0.05-0.15 M NaOH solution.
- Liu, Xiao-Cui,Zhu, Zhen-Yuan,Tang, Ya-Li,Wang, Ming-Fei,Wang, Zheng,Liu, An-Jun,Zhang, Yong-Min
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- Efficient biotransformation of D-fructose to D-mannose by a thermostable D-lyxose isomerase from Thermosediminibacter oceani
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D-Mannose has prebiotic effect and potential medical application. Besides, it can be used as substrate to produce mannitol, a functional polyol widely used in food industry. As this result, it has attracted many researchers’ attention. In this work, a thermostable D-mannose-producing D-lyxose isomerase (D-LI) was characterized from a hyperthermophile, Thermosediminibacter oceani. The recombinant D-LI could be remarkably activated by Mn2+. It displayed maximal activity in presence of 1 mM Mn2+ at pH 6.5 and 65 °C, and was determined to be highly thermostable at 80 °C. The half-life was calculated to be 5.64, 2.82, 0.77, and 0.2 h at 70, 75, 80, and 85 °C, respectively. The enzyme showed the optimum activity using D-lyxose as substrate and could also effectively catalyze the isomerization between D-fructose and D-mannose. Under optimum conditions, 101.6 g/L D-mannose was produced from 400 g/L D-fructose after reaction for 9 h, giving a conversion yield of 25.4%.
- Yu, Lina,Zhang, Wenli,Zhang, Tao,Jiang, Bo,Mu, Wanmeng
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p. 2026 - 2033
(2016/12/16)
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- Production of keto-disaccharides from aldo-disaccharides in subcritical aqueous ethanol
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Isomerization of disaccharides (maltose, isomaltose, cellobiose, lactose, melibiose, palatinose, sucrose, and trehalose) was investigated in subcritical aqueous ethanol. A marked increase in the isomerization of aldo-disaccharides to keto-disaccharides was noted and their hydrolytic reactions were suppressed with increasing ethanol concentration. Under any study condition, the maximum yield of keto-disaccharides produced from aldo-disaccharides linked by β-glycosidic bond was higher than that produced from aldo-disaccharides linked by α-glycosidic bond. Palatinose, a keto-disaccharide, mainly underwent decomposition rather than isomerization in subcritical water and subcritical aqueous ethanol. No isomerization was noted for the non-reducing disaccharides trehalose and sucrose. The rate constant of maltose to maltulose isomerization almost doubled by changing solvent from sub-critical water to 80 wt% aqueous ethanol at 220°C. Increased maltose monohydrate concentration in feed decreased the conversion of maltose and the maximum yield of maltulose, but increased the productivity of maltulose. The maximum productivity of maltulose was ca. 41 g/(h kg-solution).
- Gao, Da-Ming,Kobayashi, Takashi,Adachi, Shuji
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p. 998 - 1005
(2016/05/09)
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- Supported Tetrahedral Oxo-Sn Catalyst: Single Site, Two Modes of Catalysis
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Mild calcination in ozone of a (POSS)-Sn-(POSS) complex grafted on silica generated a heterogenized catalyst that mostly retained the tetrahedral coordination of its homogeneous precursor, as evidenced by spectroscopic characterizations using EXAFS, NMR, UV-vis, and DRIFT. The Sn centers are accessible and uniform and can be quantified by stoichiometric pyridine poisoning. This Sn-catalyst is active in hydride transfer reactions as a typical solid Lewis acid. However, the Sn centers can also create Br?nsted acidity with alcohol by binding the alcohol strongly as alkoxide and transferring the hydroxyl H to the neighboring Sn-O-Si bond. The resulting acidic silanol is active in epoxide ring opening and acetalization reactions.
- Beletskiy, Evgeny V.,Hou, Xianliang,Shen, Zhongliang,Gallagher, James R.,Miller, Jeffrey T.,Wu, Yuyang,Li, Tiehu,Kung, Mayfair C.,Kung, Harold H.
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supporting information
p. 4294 - 4297
(2016/05/09)
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- Shape-selective Valorization of Biomass-derived Glycolaldehyde using Tin-containing Zeolites
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A highly selective self-condensation of glycolaldehyde to different C4 molecules has been achieved using Lewis acidic stannosilicate catalysts in water at moderate temperatures (40–100 °C). The medium-sized zeolite pores (10-membered ring framework) in Sn-MFI facilitate the formation of tetrose sugars while hindering consecutive aldol reactions leading to hexose sugars. High yields of tetrose sugars (74 %) with minor amounts of vinyl glycolic acid (VGA), an α-hydroxyacid, are obtained using Sn-MFI with selectivities towards C4 products reaching 97 %. Tin catalysts having large pores or no pore structure (Sn-Beta, Sn-MCM-41, Sn-SBA-15, tin chloride) led to lower selectivities for C4 sugars due to formation of hexose sugars. In the case of Sn-Beta, VGA is the main product (30 %), illustrating differences in selectivity of the Sn sites in the different frameworks. Under optimized conditions, GA can undergo further conversion, leading to yields of up to 44 % of VGA using Sn-MFI in water. The use of Sn-MFI offers multiple possibilities for valorization of biomass-derived GA in water under mild conditions selectively producing C4 molecules.
- Tolborg, S?ren,Meier, Sebastian,Saravanamurugan, Shunmugavel,Fristrup, Peter,Taarning, Esben,Sádaba, Irantzu
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p. 3054 - 3061
(2016/11/17)
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