- Orthogonal Active-Site Labels for Mixed-Linkage endo-β-Glucanases
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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)
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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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- 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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- An Effective Heterogeneous Catalyst of [BMIM]3PMo12O40 for Selective Sugar Epimerization
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The development of heterogeneous catalysts for the epimerization of sugars has received much less attention than that for the isomerization of sugars. To date, molybdates are the most effective catalysts for the epimerization of sugars, although they lack stability toward hydrolysis of their active sites in water. To solve the issue of the formation of a highly water-soluble heteropolyblue (PMored) for phosphomolybdates (PMos) in aqueous reaction systems, herein, a 1-butyl-3-methylimidazolium phosphomolybdate ([BMIM]3PMo12O40) was synthesized through an ion-exchange method. This catalyst was effective and selective for the C2-epimerization of sugars under mild reaction conditions (red was detected by means of UV/Vis spectroscopy. Moreover, the catalyst can be simply separated by filtration and reused for at least eight cycles without a drop in catalytic activity. XRD, FTIR, and X-ray photoelectron spectroscopy measurements indicate that the catalyst is stable under the reaction conditions. In a comparison of the catalytic activity and surface wettability with those of other PMo salts, that is, 1-ethyl-3-methylimidazolium phosphomolybdate ([EMIM]3PMo12O40), 1-hexyl-3-methylimidazolium ([HexMIM]3PMo12O40), [choline]3PMo12O40, and cetyltrimethylammonium phosphomolybdate ([CTA]3PMo12O40), it is found that [BMIM]3PMo12O40 has more appropriate hydrophobic–hydrophilic balance, which should be responsible for better catalytic activity and stability.
- Bayu, Asep,Yoshida, Akihiro,Karnjanakom, Surachai,Zuo, Zhijun,Hao, Xiaogang,Abudula, Abuliti,Guan, Guoqing
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p. 383 - 389
(2018/05/04)
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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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- 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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- 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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- Acid-Assisted Ball Milling of Cellulose as an Efficient Pretreatment Process for the Production of Butyl Glycosides
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Ball milling of cellulose in the presence of a catalytic amount of H2SO4 was found to be a promising pre-treatment process to produce butyl glycosides in high yields. Conversely to the case of water, n-butanol has only a slight effect on the recrystallization of ball-milled cellulose. As a result, thorough depolymerization of cellulose prior the glycosylation step is no longer required, which is a pivotal aspect with respect to energy consumption. This process was successfully transposed to wheat straw from which butyl glycosides and xylosides were produced in good yields. Butyl glycosides and xylosides are important chemicals as they can be used as hydrotropes but also as intermediates in the production of valuable amphiphilic alkyl glycosides.
- Boissou, Florent,Sayoud, Nassim,De Oliveira Vigier, Karine,Barakat, Abdellatif,Marinkovic, Sinisa,Estrine, Boris,Jér?me, Fran?ois
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p. 3263 - 3269
(2015/10/19)
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- Catalytic effect of aluminium chloride on the example of the conversion of sugar model compounds
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Abstract In this work, the catalytic effect of the Bronsted acid hydrochloric acid, the Bronsted base sodium hydroxide and the Lewis acid AlCl3 on the conversion of biomass derived carbohydrates is investigated. On the example of the glycolaldehyde conversion, it is shown that the Lewis acid catalyses the ketol-endiol-tautomerism, the dehydration, the retro-aldol-reaction and the benzilic-acid-rearrangement. The main products are C4- and C6-carbohydrates as well as their secondary products 2-hydroxybut-3-enoic acid 1 and several furans. Under the same reaction conditions hydrochloric acid catalyzes mainly the dehydration and sodium hydroxide the tautomerism and subsequent aldolization.
- Schwiderski, Martin,Kruse, Andrea
-
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- Productive sugar isomerization with highly active Sn in dealuminated β zeolites
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A water-tolerant Lewis acid catalyst was synthesized by grafting Sn IV in isopropanol under reflux onto dealuminated zeolites with the BEA (β) topology. This synthesis method allows the production of highly active Snβ-type catalysts without the need for long hydrothermal syntheses or hydrogen fluoride, while using cheap Sn-precursors, industrially available β zeolites and standard catalyst synthesis unit operations. Extensive characterization of the best catalyst shows highly dispersed Sn in the zeolite matrix (XRD, 29Si MAS NMR and 1H MAS NMR) without the formation of SnO2 (XRD and UV-Vis). The catalyst was tested for the model isomerization of sugars such as glucose to fructose. The catalytic activity proved to be purely heterogeneous and the catalyst was recycled and reused without significant loss in activity. Isomerization productivities above 4 kg product per kg of catalyst per hour are reported with appreciably low Sn loadings, corresponding to exceptionally high turnover frequencies, viz. 500 cycles per Sn per hour at 110 °C, which surpass the activity per Sn of the original hydrothermally synthesized Snβ.
- Dijkmans, Jan,Gabriels, Dries,Dusselier, Michiel,De Clippel, Filip,Vanelderen, Pieter,Houthoofd, Kristof,Malfliet, Annelies,Pontikes, Yiannis,Sels, Bert F.
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p. 2777 - 2785
(2013/10/08)
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- Development of a chemical strategy to produce rare aldohexoses from ketohexoses using 2-aminopyridine
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Rare sugars are monosaccharides that are found in relatively low abundance in nature. Herein, we describe a strategy for producing rare aldohexoses from ketohexoses using the classical Lobry de Bruyn-Alberda van Ekenstein transformation. Upon Schiff-base formation of keto sugars, a fluorescence-labeling reagent, 2-aminopyridine (2-AP), was used. While acting as a base catalyst, 2-AP efficiently promoted the ketose-to-aldose transformation, and acting as a Schiff-base reagent, it effectively froze the ketose-aldose equilibrium. We could also separate a mixture of Sor, Gul, and Ido in their Schiff-base forms using a normal-phase HPLC separation system. Although Gul and Ido represent the most unstable aldohexoses, our method provides a practical way to rapidly obtain these rare aldohexoses as needed.
- Hasehira, Kayo,Miyanishi, Nobumitsu,Sumiyoshi, Wataru,Hirabayashi, Jun,Nakakita, Shin-Ichi
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experimental part
p. 2693 - 2698
(2011/12/21)
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- HYBRID COMPOUNDS BASED ON POLYOL(S) AND AT LEAST ONE OTHER MOLECULAR ENTITY, POLYMERIC OR NON-POLYMERIC, IN PARTICULAR OF THE POLYORGANOSILOXANE TYPE, PROCESS FOR THE PREPARATION THEREOF, AND APPLICATIONS THEREOF
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The invention relates to novel hybrid compounds comprising at least one polyon entity (Po)—for example oligomer or polymer—in which at least one of the hydroxyl functions of Po is substituted by at least one entity A that can be of a variable nature, for example polymer (e.g. polyorganosiloxane-POS), hydrocarbonated or mineral. The bond Ro between the entity Po and the entity A is obtained by means of “click chemistry” and corresponds to formula (II.1) or (II.2), Z representing —CH— or —N—. A is an entity selected from the group comprising the various polyols of Po, polyorganosiloxanes (POS), polyalkylene glycols, polyamides, polyesters, polystyrenes, alkyls, alkenyls, alkynyls, aryls, and combinations thereof, in addition to mineral materials such as silica and the combinations thereof. Said hybrid components can be used as emulsifiers, especially for cosmetics.
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- Aldose-ketose interconversion in pyridine in the presence of aluminium oxide
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The reaction rate of the Lobry de Bruyn-Alberda van Ekenstein transformation of aldoses to ketoses in boiling pyridine was strongly increased by the addition of aluminium oxide. In addition to aldose-ketose transformation, 2-epimers of the starting aldoses and 3-epimers of the primarily produced ketoses were formed to some extent, as reported also when these reactions are carried out without aluminium oxide. The relative amounts of the primary ketose and the starting aldose in the reaction mixtures may be explained on the basis of their stability, predicted from reported free energy calculations. Isomerisation of ketoses to aldoses was much slower than the reverse reaction. The relative free energies are also in these cases important, the very stable xylo-2-hexulose gave only 7% and 6% of the aldoses gulose and idose, respectively, after boiling for 7 h in pyridine in the presence of aluminium oxide.
- Ekeberg, Dag,Morgenlie, Svein,Stenstrom, Yngve
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p. 1992 - 1997
(2008/02/10)
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- COSMETIC COMPOSITION CONTAINING HYDROLYSATES OF ICARIIN
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The present invention relates to a cosmetic composition containing hydrolysates of icariin, and more particularly, a cosmetic composition containing hydrolysates of icariin including icaritin, icariside I and icariside II. The hydrolysates of icariin is prepared by a method comprising the steps of: (a) obtaining an extract from a plant containing icariin using water or an organic solvent; and (b) hydrolyzing the plant extract with an acid, a base, an enzyme or a microorganism producing the enzyme. The cosmetic composition according to the present invention is employed for anti-oxidant, anti-aging, whitening or anti-wrinkling effects.
- -
-
Page/Page column 15
(2008/06/13)
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- The effect of microwave irradiation on Mo(VI) catalyzed transformations of reducing saccharides
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Efficient microwave-assisted Mo(VI)-catalyzed transformations of the 10 most common aldoses are described. Both pentoses and hexoses were converted to the corresponding epimers in considerably shorter reaction times. The yields were comparable, or better compared to conventional synthetic methods.
- Hricoviniova, Zuzana
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p. 2131 - 2134
(2007/10/03)
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- Mitochondrially targeted antioxidants
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The invention provides mitochondrially targeted antioxidant compounds comprising a lipophilic cation moiety covalently coupled to a glutathione peroxidase mimetic. These compounds can be used to treat patients who would benefit from the reduction of oxidative stress.
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- Kinetic and chemical studies on the isomerization of monosaccharides in N-methylmorpholine-N-oxide (NMMO) under Lyocell conditions
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The Lyocell process is a modern and environmentally fully compatible industrial fiber-making technology. Cellulosic pulp is dissolved without chemical derivatization in a melt of N-methylmorpholine-N-oxide monohydrate (NMMO). In the present work, the reactions of monosaccharides under Lyocell conditions were investigated in detail, using capillary zone electrophoresis as the analytical technique to clarify the composition of reaction mixtures and to follow the kinetics. Under Lyocell conditions, xylose and glucose undergo two competitive reactions: rapid conversion to nonreducing products, and complete isomerization involving the whole carbohydrate backbone, via ketose intermediates. Sugar acids are present in minor amounts only, as demonstrated by employing isotopically labeled material for NMR techniques.
- Adorjan, Immanuel,Sjoeberg, John,Rosenau, Thomas,Hofinger, Andreas,Kosma, Paul
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p. 1899 - 1906
(2007/10/03)
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- New cytotoxic oleanane saponins from the infructescences of Polyscias amplifolia from the Madagascar rainforest
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Bioassay-guided fractionation of an ethanolic extract of the infructescences of Polyscias amplifolia resulted in the isolation of two new oleanolic acid saponins, polyfoliolides A (1) and B (2), in addition to the two known saponins 3-O-β-D-galactopyrano-syloleanolic acid (3) and 3-O-β-D-galactopyranosyl-(1→4)-β-D-galactopyranosyloleanolic acid (4). The structures of the two new compounds were established as 3-O-β-D-galactopyranosyl-(1→4)-β-D-xylopyranosyloleanolic acid (1) and 3-O-β-D-galactopyranosyl-(1→4)-α-L-arabinopyranosyloleanolic acid (2) on the basis of extensive 1D and 2D NMR spectroscopic data interpretation and chemical conversions. All the isolated compounds showed weak cytotoxicity against A2780 human ovarian cancer cell line, with IC50 values in the range 6.7 to 10.8 μg/mL.
- Chaturvedula, V. S. Prakash,Schilling, Jennifer K.,Miller, James S.,Andriantsiferana, Rabodo,Rasamison, Vincent E.,Kingston, David G. I.
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p. 440 - 444
(2007/10/03)
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- A new convergent route to aldohexoses from a common chiral building block.
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[reaction in text] A diastereocontrolled route to the eight aldohexoses has been developed starting from a common cyclohexanoid chiral building block.
- Honzumi,Taniguchi,Ogasawara
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p. 1355 - 1358
(2007/10/03)
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- Methods for treating plants and enhancing plant growth using polyacylglycosides and/or polyalkylglycosides and formulations for same
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Methods and formulations for treating plants and enhancing plant growth and for safening high concentrations of one or more phytocatalysts, wherein one or more formulations, comprising, a high concentration of one or more phytocatalysts, and an effective amount of one or more polyacylglycosides and polyalkylglycosides; and isomers, and metabolites, salts, hydrates, esters, amines, and derivatives of the polyacylglycosides and polyalkylglycosides, and combinations thereof, is applied to the plants.
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- Saponins isolated from Allium chinense G. DON and antitumor-promoting activities of isoliquiritigenin and laxogenin from the same drug
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Investigation of the Chinese crude drug 'Xiebai,' the bulbs of Allium chinense G. DON (Liliaceae), led to the isolation of 2 saponins, xiebai- saponin I (laxogenin 3-O-β-xylopyranosyl (1→4)-[α-arabinopyranosyl (1→6)]-β-glucopyranoside) (1) and laxogenin 3-O-α-arabinopyranosyl (1→6)- β-glucopyranoside (2), and the aglycone, laxogenin (3), together with 2 chalcones, isoliquiritigenin (4) and isoliquiritigenin-4-O-glucoside (5), and β-sitosterol glucoside (6). Compounds 15 were tested in vitro for their inhibitory effect on the 12-O-tetradecanoylphorbol-13-acetate (TPA)- stimulated 32Pi-incorporation into phospholipids of HeLa cells. In addition to this, laxogenin (3) was proven to have an antitumor-promoting activity in a two-stage lung carcinogenesis experiment.
- Baba, Masaki,Ohmura, Masayoshi,Kishi, Naoki,Okada, Yoshihito,Shibata, Shoji,Peng, Jeng,Yao, Shin-Sen,Nishino, Hoyoku,Okuyama, Toru
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p. 660 - 662
(2007/10/03)
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- Total synthesis of the L-hexoses
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Enantiomerically pure polyhydroxylated natural products are synthesized by using a reiterative two-carbon extension cycle consisting of four key transformations. The generality and efficiency of this methodology are demonstrated in the total synthesis of all eight L-hexoses.
- Ko, Soo Y.,Lee, Albert W. M.,Masamune, Satoru,Reed III, Lawrence A.,Sharpless, K. Barry,Walker, Frederick J.
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p. 245 - 264
(2007/10/02)
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- EVIDENCE OF STABLE HYDROGEN-BONDED IONS DURING ISOMERZATION OF HEXOSES IN ALKALI
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Epimeric pairs of aldohexoses and related ketohexose were isomerized in aqueous KOH at various temperatures and pH values, and the mixtures then analyzed by h.p.l.c. on either a cation-exchange resin or a reversed-phase column.It was found that the propertions of starting aldohexoses remaining after several days often exceeded those of the same that were formed from the epimeric aldoses and the corresponding ketoses.The difference with allose, gulose, and mannose was much larger than with other aldohexoses.These differences are rationalized by assuming that anomers having the OH groups attached to C-1, C-2, and C-3 in an axial-equatorial-axial or an equatorial-axial-equatorial arrangement form especially stable, hydrogen-bonded ions or molecular complexes that disturb the equilibrium state and affect the isomerization and mutarotation reactions.
- El Khadem, Hassan S.,Ennifar, Sofiane,Isbell, Horace S.
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- STUDY OF THE EFFECT OF ORGANIC SOLVENTS ON THE SYNTHESIS OF LEVAN AND THE HYDROLYSIS OF SUCROSE BY Bacillus subtilis LEVANSUCRASE
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The equilibrium between the hydrolase and synthetase activities of levansucrase was determined by progressively substituting water with various organic solvents in the enzymic reaction medium.In the presence of high concentrations of these solvents, the enzyme displayed anly synthetase activity.The levan obtained under such conditions had Mr-106 and presented a low molecular dipersity.In the presence of solvent, the Km values for sucrose and raffinose remained unchanged, but the kcat values were five times higher in comparison to the same constants determined for an aqueous medium.
- Chambert, Regis,Petit-Glatron, Marie-Francoise
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p. 117 - 124
(2007/10/02)
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- Glycosyl Nervogenic Acid Esters of Carbohydrates from Anodendron affine (Anodendron. VI)
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Esters of p-O-glucosyl- and p-O-primverosylnervogenic acid with some carbohydrates (including dambonitol, glucose, and sucrose) were isolated from the seeds, unripened fruits, and caules of Anodendron affine DRUCE.The locations of the nervogenic acid moiety on dambonitol and sucrose were determined on the basis of spectral and chemical evidence.Keywords--Anodendron affine; Apocynacea; 3,5-diprenyl-4-hydroxybenzoic acid; nervogenic acid; 1,3-di-O-methyl-myo-inositol; dambonitol; 5-acyldambonitol; 6-acyldambonitol; 6glc-O-(p-O-glucosyl)nervogenoylsucrose; anodendrosin
- Abe, Fumiko,Yamauchi, Tatsuo
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p. 2712 - 2720
(2007/10/02)
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- Kinetics, Catalysis, and Mechanism of the Secondary Reaction in the Final Phase of the Formose Reaction
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In the final phase of the formose reaction sugars are formed by the reaction of glycolaldehyde, glyceraldehyde and dihydroxyacetone.The application of high-pressure liquid chromatography allows for the first time to investigate intermediate and final products quantitatively.The results of kinetical investigations allow to suggest a reaction mechanism for the secondary reaction in the final phase of the formose reaction.This mechanism is compared with that of the starting phase and other known mechanisms.From the results metal ion-catalyzed aldol reactions have to be assumed.
- Harsch, Guenther,Bauer, Hermann,Voelter, Wolfgang
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p. 623 - 635
(2007/10/02)
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- THE FORMOIN REACTION
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The formoin reaction, i.e., the autocondensation of formaldehyde in an aprotic solvent catalysed by the conjugate base of a thiazolium ion, has been studied in detail.Glucose, galactose, dihyroxyacetone dimer, xylose, and arabinose have been identified as products.The influence of catalysts, temperature, basicity, and reaction time is documented.N,N-Dimethylformamide is a more convenient solvent than ether, benzene, or diglyme.Ethyldi-isopropylamine affords better yields of carbohydrate material than triethylamine.At =60 deg, aldol condensations are reduced to a minimum.After 1-2 h of reaction (depending on the conditions), the yields begin to decrease and become zero after ca. 24 h.
- Castells, Josep,Lopez-Calahorra, Francisco,Geijo, Fernando
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p. 197 - 208
(2007/10/02)
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- Kinetics of reactions of manganese(III) pyrophosphate with some hexitols
-
Alditols are acyclic, polyhydric alcohols that are derived from aldoses and ketoses by reduction.Their wide-spread occurance in Nature, particularly in the lower forms of life, points to their biological importance.Compared to studies of the metal-ion oxidation of sugars, it seems that the oxidation of alditols has received little attention.Earlier, the oxidation of hexitols with cerium(IV) (ref. 1), cobalt(III) (ref. 2), and vanadium(V) (ref. 3) was reported, and we now describe oxidations with manganese(III) pyrophosphate.
- Fadnis, Anand G.,Kulshrestha, Sudhir K.
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p. 137 - 140
(2007/10/02)
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- STRUCTURE D'UN NOUVEL HETEROSIDE D'ISOFLAVONE : LE SAROTHAMNOSIDE
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The structure of sarothamnoside (genistein 7,4'-di-O-4-O-β-D-glucopyranosyl-β-D-apiofuranoside), a new isoflavone glycoside from Sarothamnus scoparius and S. patens, has been established by spectral analysis, mainly 13C NMR.
- Brum-Bousquet, M.,Lallemand, Y.,Tillequin, F.,Delaveau, P.
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p. 1223 - 1226
(2007/10/02)
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- The "formoin reaction" : A promising entry to carbohydrates from formaldehyde
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Formaldehyde condensation catalyzed by the conjugate bases of thiazolium ions, leads to a complex mixture ("formoin mixture") of unbranched aldoses and ketoses, in which glucose, galactose, glyceraldehyde dimer, xylose and arabinose have been identified.
- Castells, Joseph,Geijo, Fernando,Lopez-Calahorra, Francisco
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p. 4517 - 4520
(2007/10/02)
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