scholarly journals The selective cleavage of glycopyranosiduronamide linkages in methylated polysaccharides

1978 ◽  
Vol 56 (5) ◽  
pp. 685-690 ◽  
Author(s):  
Gerald Oliver Aspinall ◽  
Karl-Gunnar Rosell
Keyword(s):  
Uronic Acid ◽  
Capsular Polysaccharide ◽  
Gum Arabic ◽  
Hydroxyl Groups ◽  
Selective Degradation ◽  
Derivatives Of

Hofmann degradation of glycosiduronamide linkages in methylated polysaccharides furnishes pentodialdose derivatives to which any sugar residues external to uronic acid residues remain attached together with degraded methylated polysaccharides carrying aglyconic hydroxyl groups. The selective degradation has been carried out on methylated derivatives of birch xylan, gum arabic, and the capsular polysaccharide from Klebsiella type 47. Procedures for the degradation of methylated polysaccharides in the vicinity of uronic acid residues are assessed.

The formation of hex-5-enopyranosides and their selective hydrolysis in methylated polysaccharides

1978 ◽  
Vol 56 (5) ◽  
pp. 680-684 ◽  
Author(s):  
Gerald Oliver Aspinall ◽  
Karl-Gunnar Rosell
Keyword(s):  
Uronic Acid ◽  
Gum Arabic ◽  
Hydroxyl Groups ◽  
Triphenyl Phosphite ◽  
Reaction Sequence ◽  
Selective Hydrolysis ◽  
Acidic Polysaccharides ◽  
Hydrolysis Of ◽  
Derivatives Of

The introduction of hex-5-enopyranoside residues into methylated acidic polysaccharides is effected by reduction of uronic acid residues, followed by reaction with triphenyl phosphite methiodide, and dehydroiodination. The selective hydrolysis of hex-5-enopyranosidic linkages with characterization of the 6-deoxyglycos-5-uloses thus formed and location of the aglyconic hydroxyl groups thus exposed has been demonstrated for methylated derivatives of birch xylan and gum arabic. The reaction sequence provides a new method for linkage analysis of acidic polysaccharides.

The selective cleavage of permethylated glycopyranosiduronic acid linkages by oxidative decarboxylation with lead tetraacetate

1981 ◽  
Vol 59 (6) ◽  
pp. 935-940 ◽  
Author(s):  
Gerald Oliver Aspinall ◽  
Hany Kamal Fanous ◽  
Nimal Savitri Kumar ◽  
Velupillai Puvanesarajah
Keyword(s):  
Sodium Borohydride ◽  
Gum Arabic ◽  
Lead Tetraacetate ◽  
Oxidative Decarboxylation ◽  
Hydroxyl Groups ◽  
Reaction Sequence ◽  
Pectic Acid ◽  
Acid Methyl ◽  
Sterculia Urens ◽  
Derivatives Of

Reaction of permethylated glycopyranosiduronic acids with lead tetraacetate furnishes epimeric 5-acetoxypentopyranosides as products of oxidative decarboxylation. Glycoside cleavage then occurs on treatment with sodium borohydride which affords the corresponding pentitols with exposure of aglyconic hydroxyl groups. The reaction sequence has been performed with permethylated derivatives of methyl β-melibiosiduronic acid, methyl β-gentiobiosiduronic acid, gum arabic, leiocarpan A, Sterculia urens gum, and citrus pectic acid. The scope of the reaction sequence in polysaccharide studies is discussed.

The role of secondary alcoholic groups of D-galacturonan in its degradation with exo-D-galacturonanase

1980 ◽  
Vol 45 (2) ◽  
pp. 427-434 ◽  
Author(s):  
Kveta Heinrichová ◽  
Rudolf Kohn
Keyword(s):  
Acetyl Derivative ◽  
Competitive Inhibitor ◽  
Hydroxyl Groups ◽  
Pectic Acid ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
The Individual ◽  
Degradation Degree ◽  
Derivatives Of

The effect of exo-D-galacturonanase from carrot on O-acetyl derivatives of pectic acid of variousacetylation degree was studied. Substitution of hydroxyl groups at C(2) and C(3) of D-galactopyranuronic acid units influences the initial rate of degradation, degree of degradation and its maximum rate, the differences being found also in the time of limit degradations of the individual O-acetyl derivatives. Value of the apparent Michaelis constant increases with increase of substitution and value of Vmax changes. O-Acetyl derivatives act as a competitive inhibitor of degradation of D-galacturonan. The extent of the inhibition effect depends on the degree of substitution. The only product of enzymic reaction is D-galactopyranuronic acid, what indicates that no degradation of the terminal substituted unit of O-acetyl derivative of pectic acid takes place. Substitution of hydroxyl groups influences the affinity of the enzyme towards the modified substrate. The results let us presume that hydroxyl groups at C(2) and C(3) of galacturonic unit of pectic acid are essential for formation of the enzyme-substrate complex.

Proton spin–spin coupling constants and intramolecular hydrogen bonding in bromine derivatives of 1,3-dihydroxybenzene

1976 ◽  
Vol 54 (14) ◽  
pp. 2228-2230 ◽  
Author(s):  
Ted Schaefer ◽  
J. Brian Rowbotham
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Proton Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Derivatives Of

The conformational preferences in CCl4 solution at 32 °C of the hydroxyl groups in bromine derivatives of 1,3-dihydroxybenzene are deduced from the long-range spin–spin coupling constants between hydroxyl protons and ring protons over five bonds. Two hydroxyl groups hydrogen bond to the same bromine substituent in 2-bromo-1,3-dihydroxybenzene but prefer to hydrogen bond to different bromine substituents when available, as in 2,4-dibromo-1,3-dihydroxybenzene. When the OH groups can each choose between two ortho bromine atoms, as in 2,4,6-tribromoresorcinol, they apparently do so in a very nearly statistical manner except that they avoid hydrogen bonding to the common bromine atom.

scholarly journals Characteristic Flavonoids from Acacia burkittii and A. Acuminata Heartwoods and their Differential Cytotoxicit to Normal and Leukemia Cells

2009 ◽  
Vol 4 (1) ◽  
pp. 1934578X0900400
Author(s):  
Mary H. Grace ◽  
George R. Wilson ◽  
Fayez E. Kandil ◽  
Eugene Dimitriadis ◽  
Robert M. Coates
Keyword(s):  
Cell Line ◽  
Relative Concentration ◽  
Hydroxyl Groups ◽  
L1210 Cells ◽  
Green Monkey ◽  
Bioassay Guided Fractionation ◽  
Acetone Extracts ◽  
Derivatives Of ◽  
Hplc Analyses ◽  
Mouse Lymphoma

Bioassay-guided fractionation of extracts from Acacia burkittii and A. acuminata heartwoods against an L1210 (mouse lymphoma) cell line led to the isolation of two flavan-3,4-diols, melacacidin (1) and isomelacacidin (2), and three flavonoids, 3,7,8,3′,4′-pentahydroxyflavone (3), 7,8,3′,4′-tetrahydroxyflavanone (4) and 3,7,8,3′,4′-pentahydroxyflavanone (5). HPLC analyses (280 nm) of the 70% acetone extracts of the two plants showed different profiles in terms of the relative concentration of the five identified compounds. When tested against L1210, compounds 1 and 2 were the most active, giving ID50 values of 2.5 and 4.5 μg/mL, respectively. The lower activity of the other isolated compounds indicated the importance of the 3,4-hydroxyl groups for the cytotoxic activity of these flavonoids. The isolated compounds were either non-toxic or had very low toxicities against the “normal” CV-1 cell line (green monkey kidney cells). The O-methyl and O-acetyl derivatives of these compounds were inactive. Ten commercially available phenolic compounds (6-15) were also tested for their activity against both CV-1 and L1210 cell lines. Flavan-3,4-diols 1 and 2 were more cytotoxic to L1210 cells than all tested compounds, including catechin and epicatechin, the most abundant flavan-3-ols in many fruits and vegetable.

scholarly journals Regulation of Staphylococcus aureus Type 5 and Type 8 Capsular Polysaccharides by CO2

2001 ◽  
Vol 183 (15) ◽  
pp. 4609-4613 ◽  
Author(s):  
Silvia Herbert ◽  
Steven W. Newell ◽  
Chia Lee ◽  
Karsten-Peter Wieland ◽  
Bruno Dassy ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Genetic Background ◽  
Capsular Polysaccharide ◽  
Promoter Sequence ◽  
Transcriptional Level ◽  
Marginal Effect ◽  
Promoter Regions ◽  
Sequence Variations ◽  
Derivatives Of

ABSTRACT Staphylococcus aureus expression of capsular polysaccharide type 5 (CP5) has been shown to be downregulated by CO2. Here we show that CO2 reduces CP5 expression at the transcriptional level and that CO2regulates CP8 expression depending on the genetic background of the strains. Growth in the presence of air supplemented with 5% CO2 caused a significant decrease in CP8 expression in fourS. aureus strains, a marginal effect in four strains, and higher CP8 expression in strain Becker. Absolute CP8 expression in the nine S. aureus strains differed largely from strain to strain. Four groups of strains were established due to sequence variations in the promoter region of cap5 andcap8. To test whether these sequence variations are responsible for the different responses to CO2, promoter regions from selected strains were fused to the reporter genexylE in pLC4, and the plasmids were electrotransformed into strains Becker and Newman. XylE activity was negatively regulated by CO2 in all derivatives of strain Newman and was always positively regulated by CO2 in all derivatives of strain Becker. Differences in promoter sequences did not influence the pattern of CP8 expression. Therefore, the genetic background of the strains rather than differences in the promoter sequence determines the CO2 response. trans-acting regulatory molecules may be differentially expressed in strain Becker versus strain Newman. The strain dependency of the CP8 expression established in vitro was also seen in lung tissue sections of patients with cystic fibrosis infected with CP8-positive S. aureus strains.

Molecular recognition XI. The synthesis of extensively deoxygenated derivatives of the H-type 2 human blood group determinant and their binding by an anti-H-type 2 monoclonal antibody and the lectin 1 of Ulexeuropaeus

1992 ◽  
Vol 70 (1) ◽  
pp. 254-271 ◽  
Author(s):  
Ulrike Spohr ◽  
Eugenia Paszkiewicz-Hnatiw ◽  
Naohiko Morishima ◽  
Raymond U. Lemieux
Keyword(s):  
Monoclonal Antibody ◽  
Molecular Recognition ◽  
Blood Group ◽  
Human Blood ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Human Blood Group ◽  
Derivatives Of ◽  
Hydrogen Bonded

The relative potencies of a wide variety of deoxygenated derivatives of the methyl glycoside of α-L-Fuc-(1 → 2)-β-D-Gal-(1 → 4)- β-D-GlcNAc (the H-type 2 human blood group related trisaccharide) for the inhibition of the binding of an artificial H-type 2 antigen by the lectin I of Ulexeuropaeus confirmed the previous evidence that the key and productive interaction involves only the three hydroxyl groups of the α-L-fucose unit, the hydroxyl at the 3-position of the β-D-galactose residue, and the nonpolar groups in their immediate environment. Except for the acetamido group and the hydroxymethyl of the β-D-Gal unit, which stay in the aqueous phase, on complex formation the remaining three hydroxyl groups appear to come to reside at or near the periphery of the combining site since their replacement by hydrogen causes relatively small changes (< ± 1 kcal/mol) in the stability of the complex (ΔG0). Relatively much larger but compensating changes occur for the enthalpy and entropy terms, and these may arise primarily from the differences in the water structure about the periphery of the combining site and the oligosaccharide both prior to and after complexation. It is proposed that steric constraints lead to an ordered state of the water molecules hydrogen-bonded to the polar groups within the cleft formed by the key region of the amphiphilic combining site. Their release to form less ordered clusters of more strongly hydrogen-bonded water molecules in bulk solution would contribute importantly to the driving force for complexation. It is demonstrated that the surface used for the binding of H-type 2-OMe by a monoclonal anti-H antibody is virtually identical to that used by the Ulex lectin. Keywords: molecular recognition, H-type 2 blood group determinant and deoxygenated derivatives, lectin I of Ulexeuropaeus, anti-H-type 2 monoclonal antibody, enthalpy–entropy compensation.

Synthesis and Biological Evaluation of Acetylcholinesterase Inhibitor Macakurzin C and Its Derivatives

Synlett ◽  
2015 ◽  
Vol 26 (08) ◽  
pp. 1131-1134 ◽  
Author(s):  
Hyoungsu Kim ◽  
Seung-Hoon Baek ◽  
Hongjun Jang
Keyword(s):  
Inhibitory Activity ◽  
Acetylcholinesterase Inhibitor ◽  
Biological Evaluation ◽  
Hydroxyl Groups ◽  
Structural Requirements ◽  
Ache Inhibitory Activity ◽  
Synthesis And Biological Evaluation ◽  
Derivatives Of

The derivatives of macakurzin C containing a modified D ring and protected C(3)/C(5)-hydroxyl groups were synthesized and their in vitro AChE inhibitory activity and neurotoxicity were evaluated to identify the structural requirements for the activities. The results indicated that C(3)-benzyl-protected derivative has a more potent AChE inhibitory activity (IC50, 2.6 μM) and a less neurotoxicity (GI50, >100 μM) than synthetic macakurzin C (IC50, 9.1 μM; GI50, 16.6 μM).

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