3458-28-4Relevant articles and documents
Studies on kinetics and mechanism of oxidation of D-sorbitol and D-mannitol by cerium (IV) in aqueous micellar sulfuric acid media
Das, Asim K.,Islam, Monirul,Bayen, Ruhidas
, p. 445 - 453 (2008)
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.
Structural characterization of immunostimulating polysaccharide from cultured mycelia of Cordyceps militaris
Lee, Jong Seok,Kwon, Jeong Seok,Yun, Jong Seok,Pahk, Jung Woon,Shin, Won Cheol,Lee, Shin Young,Hong, Eock Kee
, p. 1011 - 1017 (2010)
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.
Substantial spatial flexibility and hydrogen bonding within the catalysis exerted by cyclodextrin artificial glycosidases
Bjerre, Jeannette,Bols, Mikael
, p. 3487 - 3500 (2010)
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.
One-pot conversion of cellobiose to mannose using a hybrid phosphotungstic acid-cerium oxide catalyst
Gernhart, Zane C.,Bhalkikar, Anuja,Burke, John J.,Sonnenfeld, Kate O.,Marin, Chris M.,Zbasnik, Richard,Cheung, Chin Li
, p. 28478 - 28486 (2015)
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
Production of monosaccharides and bio-active compounds derived from marine polysaccharides using subcritical water hydrolysis
Meillisa, Aviannie,Woo, Hee-Chul,Chun, Byung-Soo
, p. 70 - 77 (2014)
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.
Synthesis, structure, and properties of allylamino glycosides
Shul'Tsev,Panarin
, p. 510 - 519 (2013)
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.
Gargantulide A, a complex 52-membered macrolactone showing antibacterial activity from streptomyces sp.
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.
, p. 1377 - 1380 (2015)
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.
Effects of cultured Cordyceps mycelia polysaccharide A on tumor neurosis factor-α induced hepatocyte injury with mitochondrial abnormality
Tang, Huiling,Wei, Weikun,Wang, Wang,Zha, Zhengqi,Li, Ting,Zhang, Zhijie,Luo, Chen,Yin, Hongping,Huang, Fengjie,Wang, Ying
, p. 43 - 53 (2017)
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.
Ligand-conjugated pH-sensitive polymeric micelles for the targeted delivery of gefitinib 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
, p. 73184 - 73193 (2015)
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.
New secondary metabolites from Asphodelus tenuifolius
Safder, Muhammad,Mehmood, Rashad,Ali, Bakhat,Mughal, Uzma Rasheed,Malik, Abdul,Jabbar, Abdul
, p. 144 - 151 (2012)
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
