CONSTITUTION OF A HEMICELLULOSE FROM WHEAT BRAN

1955 ◽  
Vol 33 (1) ◽  
pp. 56-67 ◽  
Author(s):  
G. A. Adams
Keyword(s):  
Oxalic Acid ◽  
Wheat Bran ◽  
Uronic Acid ◽  
Periodate Oxidation ◽  
Reducing Power ◽  
Degree Of Polymerization ◽  
Alkaline Extraction ◽  
Acidic Polysaccharide ◽  
Simultaneous Production ◽  
Hydrolysis Of

The hemicellulose prepared from wheat bran by alkaline extraction was an acidic polysaccharide containing arabinose (50.0%), xylose (38.5%), and uronic acid (9.0%). Graded hydrolysis with 0.02 N oxalic acid preferentially released 65% of the arabinose with only a small simultaneous production of xylose. Hydrolysis of the full methylated hemicellulose yielded 2,3,4-tri-O-methyl-, 2,3-di-O-methyl-, 2-O-methyl-, and free D-xylose; 2,3,5-tri-O-methyl-, 2,5-di-O-methyl-, and probably 3- and 5-O-methyl-L-arabinose. These data, together with those from periodate oxidation, strongly suggested that the molecule was a highly branched araboxylan. Viscosity measurements and reducing power determinations indicated a degree of polymerization of 300.

CONSTITUTION OF A POLYURONIDE HEMICELLULOSE FROM WHEAT LEAF

1954 ◽  
Vol 32 (2) ◽  
pp. 186-194 ◽  
Author(s):  
G. A. Adams
Keyword(s):  
Uronic Acid ◽  
Glucuronic Acid ◽  
Periodate Oxidation ◽  
Reducing Power ◽  
Degree Of Polymerization ◽  
Acid Anhydride ◽  
Alkaline Extraction ◽  
Wheat Leaf ◽  
Wheat Leaves ◽  
Acid Unit

Crude hemicellulose of mature wheat leaves has been prepared by alkaline extraction of leaf holocellulose. Purification by repeated complexing with Fehling′s solution yielded a polyuronide hemicellulose [Formula: see text] composed of D-xylose (88.5%), L-arabinose (6.90%), and uronic acid anhydride (5.27%). Methylation studies indicated a molecular structure comprising a main xylan chain of 30 an-hydro- D-xylose residues to which three L-arabinose residues and one D-glucuronic acid unit were attached as side chains by glycosidic linkages. Periodate oxidation data supported the proposed structure and the yield of formic acid indicated a molecule containing approximately 32 sugar residues. Estimations of the degree of polymerization of the molecule by measurements of viscosity and reducing power agreed with the foregoing values. The structure of the hemicellulose closely resembled that of one isolated previously from wheat straw.

CONSTITUTION OF A DEGRADED POLYSACCHARIDE FROM WHEAT BRAN

1957 ◽  
Vol 35 (2) ◽  
pp. 108-114 ◽  
Author(s):  
J. Schmorak ◽  
C. T. Bishop ◽  
G. A. Adams
Keyword(s):  
Acid Hydrolysis ◽  
Wheat Bran ◽  
Glucuronic Acid ◽  
Periodate Oxidation ◽  
Glycosidic Bond ◽  
Cellulolytic Enzyme ◽  
Acidic Polysaccharide ◽  
Hydrolysis Of ◽  
End Group ◽  
Acid Unit

Graded acid hydrolysis of a soluble wheat bran hemicellulose containing L-arabinose (50%), D-xylose (38.5%), and D-glucuronic acid (9.0%) preferentially removed the L-arabinose giving an insoluble acidic polysaccharide in approximately 25% yield by weight. Methylation studies, periodate oxidation data, and hypoiodite end group estimations showed that the degraded polysaccharide was composed of repeating units of 7-8 D-xylopyranose residues joined by β,1 → 4 linkages. To this repeating unit, one D-glucuronic acid unit was attached by a 1 → 2 glycosidic bond. The cellulolytic enzyme of Myrotheciumverrucaria, which is specific for β,1 → 4 glycosidic linkages, hydrolyzed the degraded polysaccharide although it had no effect on the parent hemicellulose

STRUCTURE OF A GALACTURONAN FROM SUNFLOWER PECTIC ACID

1966 ◽  
Vol 44 (11) ◽  
pp. 1275-1282 ◽  
Author(s):  
V. Zitko ◽  
C. T. Bishop
Keyword(s):  
Galacturonic Acid ◽  
Periodate Oxidation ◽  
Degree Of Polymerization ◽  
Critical Assessment ◽  
Molar Ratio ◽  
Aqueous Methanol ◽  
Pectic Acid ◽  
Potassium Borohydride ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

Fractions of sunflower pectic acid containing 89.8%, 94.2%, and 91.4% of D-galacturonic acid were carboxyl reduced as their methyl or ethylene glycol esters by potassium borohydride. Critical assessment of the effects of three different solvents (water, 80% aqueous dimethyl sulfoxide, and 80% aqueous methanol) on the efficiency of reduction showed that the latter solvent was best. The reductions caused a decrease in the degree of polymerization from 270 to 21. Measurement of the rates of hydrolysis of partially reduced pectic acids containing 90%, 41.6%, 19.9%, 11.0%, and 0.65% of D-galacturonic acid showed that the rate of hydrolysis was directly related to the proportion of galacturonosidic linkages present. Methylation and hydrolysis of the carboxyl-reduced pectic acid fractions yielded 2,3,4,6-tetra-O-methyl-D-galactose and 2,3,6-tri-O-methyl-D-galactose in an approximate molar ratio of 1:20. Results of the periodate oxidation of the carboxyl-reduced pectic acid supported the conclusion inferred from the methylation results that the pectic acid was a linear polymer of 1 → 4 linked α-D-galacturonic acid units.

CONSTITUTION OF A WATER SOLUBLE HEMICELLULOSE FROM AMERICAN BEECHWOOD (FAGUS GRANDIFOLIA)

1957 ◽  
Vol 35 (6) ◽  
pp. 556-564 ◽  
Author(s):  
G. A. Adams
Keyword(s):  
Average Molecular Weight ◽  
Periodate Oxidation ◽  
Reducing Power ◽  
Fagus Grandifolia ◽  
Water Soluble ◽  
Hot Water ◽  
Molar Ratio ◽  
Weight Average Molecular Weight ◽  
Homogeneous Fraction ◽  
Hydrolysis Of

Extraction of beechwood chlorite holocellulose with hot water yielded a hemicellulose in 13.4% yield (based on original extractive-free wood) containing D-xylose 72%, D-galactose 11.0%, and uronic acid 13.2%. Purification of the crude hemicellulose by complexing with Fehling's solution yielded a chemically homogeneous fraction containing D-xylose 83% and 4-O-methyl-D-glucuronic acid 15.5%. Hydrolysis of the fully methylated hemicellulose yielded 2,3,4-tri-O-methyl-D-xylose, 2,3-di-O-methyl-D-xylose, 3-O-methyl-D-xylose, and 3-O-methyl-2-O-(2,3,4-tri-O-methyl-D-glucopyranosyluronic acid)-D-xylose in a molar ratio of 2:35:3:5. On the basis of the methylation data, periodate oxidation, reducing power determinations, and weight average molecular weight values a possible structure for the hemicellulose is proposed.

THE STRUCTURAL ANALYSIS OF SOME ACIDIC XYLANS BY PERIODATE OXIDATION

1962 ◽  
Vol 40 (2) ◽  
pp. 348-352 ◽  
Author(s):  
G. G. S. Dutton ◽  
A. M. Unrau
Keyword(s):  
Acid Hydrolysis ◽  
Glucuronic Acid ◽  
Periodate Oxidation ◽  
Small Degree ◽  
Degree Of Polymerization ◽  
Borohydride Reduction ◽  
Mild Acid Hydrolysis ◽  
Degree Of Branching ◽  
Hydrolysis Of ◽  
Mild Acid

By determining the amount of formaldehyde produced on periodate oxidation of borohydride-reduced apple- and cherry-wood xylans the degree of polymerization was shown to be 155 and 100 respectively. Acid hydrolysis of the polyols obtained by periodate oxidation and borohydride reduction gave ethylene glycol in amounts indicating that these xylans have a small degree of branching. Mild acid hydrolysis of the polyols demonstrated that in these xylans D-glucuronic acid as well as 4-O-methyl-D-glucuronic acid was present and that some of the former occupied non-terminal positions.

Structure of the Capsular Polysaccharide of Klebsiella K-type 56

1973 ◽  
Vol 51 (18) ◽  
pp. 3021-3026 ◽  
Author(s):  
Yuen-Min Choy ◽  
Guy G. S. Dutton
Keyword(s):  
Uronic Acid ◽  
Capsular Polysaccharide ◽  
Periodate Oxidation ◽  
Side Chain ◽  
Partial Hydrolysis ◽  
Hydrolysis Of

Methylation, periodate oxidation, and partial hydrolysis studies on the capsular polysaccharide of Klebsiella K-type 56 show the structure to be a repeating unit consisting of[Formula: see text]The nature of the anomeric linkages was determined by p.m.r. spectroscopy of isolated oligosaccharides. The position of the L-rhamnose side chain was defined by characterization of the di- and tetrasaccharides obtained by partial hydrolysis of the fully methylated polysaccharide.This structure represents the first capsular polysaccharide lacking uronic acid to be studied in the genus Klebsiella.

GUM JEOL: THE STRUCTURE OF THE DEGRADED GUM DERIVED FROM IT

1964 ◽  
Vol 42 (1) ◽  
pp. 107-112 ◽  
Author(s):  
A. K. Bhattacharyya ◽  
C. V. N. Rao
Keyword(s):  
Acid Hydrolysis ◽  
Galacturonic Acid ◽  
Uronic Acid ◽  
Periodate Oxidation ◽  
Neutral Fraction ◽  
Partial Structure ◽  
Mild Acid Hydrolysis ◽  
Acidic Fraction ◽  
Hydrolysis Of ◽  
Mild Acid

Gum Jeol has been shown to be composed of residues of D-galactose, L-arabinose, and D-galacturonic acid. On mild acid hydrolysis the gum gave an aldobiouronic acid, viz. 3-O-(D-galactopyranosyl uronic acid)-D-galactopyranose. Hydrolysis of the fully methylated degraded gum yielded 2,3,4,6-terra-(3 moles); 2,3,4-tri-(2 moles); 2,4-di-(1 mole); and 2-O-methyl-D-galactose (1 mole) in the neutral fraction of the hydrolyzate. The reduced acidic fraction yielded 2,3,4-tri-(2 moles) and 2,4-di-O-methyl-D-galactose (2 moles). Based on these results a partial structure of the degraded gum has been proposed, the additional evidence of which was deduced from periodate oxidation studies of the degraded gum.

OXIDATION OF POLYSACCHARIDES BY LEAD TETRAACETATE IN DIMETHYL SULFOXIDE

1966 ◽  
Vol 44 (15) ◽  
pp. 1748-1756 ◽  
Author(s):  
V. Zitko ◽  
C. T. Bishop
Keyword(s):  
Dimethyl Sulfoxide ◽  
Uronic Acid ◽  
Glacial Acetic Acid ◽  
Periodate Oxidation ◽  
Potassium Acetate ◽  
Lead Tetraacetate ◽  
Free Aldehyde ◽  
Aldehyde Groups ◽  
Hydrolysis Of ◽  
Oxidation System

Neutral polysaccharides can be oxidized by lead tetraacetate in dimethyl sulfoxide if 15–20% of glacial acetic acid is added to prevent oxidation of the solvent. The oxidation proceeds at a rate which is several times faster than that of periodate oxidation in aqueous solution, and the same amount of oxidant is consumed. Polysaccharides oxidized by lead tetraacetate in dimethyl sulfoxide can be recovered in excellent yield by precipitation with alcohol, and have been shown to contain free aldehyde groups. Identification of the products of reduction and hydrolysis of the oxidized polysaccharides showed that the oxidation followed the normal glycol-cleavage pattern given by lead tetraacetate in other solvents. Addition of potassium acetate to the oxidations in dimethyl sulfoxide decreased the consumption of lead tetraacetate by dextran (mainly α-(1 → 6) and α-(1 → 4)). Reduction and hydrolysis of dextrans oxidized in the presence and absence of potassium acetate yielded glycerol and erythritol in the respective ratios of 3.8:1 and 8.7:1. This result indicated that potassium acetate inhibited oxidation of the C-3, C-4 glycol groups in the dextran. Acidic polysaccharides behaved atypically in this oxidation system, and those containing a high proportion of uronic acid units were resistant to oxidation.

CONSTITUTION OF THE HEMICELLULOSE FROM MESTA FIBER (HIBISCUS CANNABINUS)

1963 ◽  
Vol 41 (9) ◽  
pp. 2346-2350 ◽  
Author(s):  
S. K. Sen
Keyword(s):  
Molecular Weight ◽  
Uronic Acid ◽  
Average Molecular Weight ◽  
Analytical Data ◽  
Degree Of Polymerization ◽  
Hibiscus Cannabinus ◽  
Molar Ratio ◽  
Alkaline Solutions ◽  
Number Average Molecular Weight ◽  
Hydrolysis Of

The chlorite holocellulose of mesta fiber (Hibiscus cannabinus) was extracted with alkaline solutions of successively increasing concentration and finally with alkaline borate solution. Hemicellulose fractions (I–IV) were thus obtained. Analytical data are recorded for each fraction.Partial acid hydrolysis of the mesta hemicellulose gave 2-O-(4-O-methyl-α-D-glucopyranosyl uronic acid)-D-xylopyranose. Methanolysis and hydrolysis of the fully methylated hemicellulose (fraction II) gave a mixture of 3-O-methyl-D-xylose, 2,3-di-O-methyl-D-xylose, 2,3,4-tri-O-methyl-D-xylose, and 2-O-(2,3,4-tri-O-methyl-α-D-glucopyranosyl uronic acid)-3-O-methyl-D-xylopyranose in the approximate molar ratio of 1.6:34:1:6.4. The number-average molecular weight of the methylated polysaccharide was 18,400 ± 500 (degree of polymerization, 110 ± 3). The number-average molecular weight of the original hemicellulose (fraction II) was found to be 23,000 ± 500 (degree of polymerization, 164 ± 3). On the basis of this and other evidences it is suggested that the polysaccharide is composed of chains of 144 (1 → 4)-linked β-D-xylopyranose residues having approximately every seventh residue carrying a terminal 4-O-methyl-α-D-glucuronic acid residue linked through position 2. A small degree of branching in the backbone of D-xylose is indicated.

THE STRUCTURE OF A SYNTHETIC GLUCAN: I. GENERAL STRUCTURAL FEATURES

1962 ◽  
Vol 40 (6) ◽  
pp. 1196-1200 ◽  
Author(s):  
G. G. S. Dutton ◽  
A. M. Unrau
Keyword(s):  
Petroleum Ether ◽  
Acid Hydrolysis ◽  
Direct Evidence ◽  
Periodate Oxidation ◽  
Structural Features ◽  
Degree Of Polymerization ◽  
Molar Ratio ◽  
Partial Hydrolysis ◽  
Large Numbers ◽  
Hydrolysis Of

Only D-glucose was obtained on acid hydrolysis of the glucan. Periodate oxidation released formaldehyde, which was believed to arise from C6 of D-glucofuranose units. From the additional formaldehyde liberated from the borohydride-reduced glucan the degree of polymerization was estimated to be about 165. Complete hydrolysis of the derived polyalcohol gave glycerol, erythritol, D-glucose, and D-xylose. Partial hydrolysis gave glycerol, erythritol, and at least seven non-reducing oligosaccharides. Direct evidence for the existence of relatively large numbers of 1 → 6 and 1 → 4 linkages was found, together with smaller numbers of 1 → 2 linkages. The methylated glucan was freely soluble in chloroform – petroleum ether (5:95), and hydrolysis gave tetra, tri, di, and mono-O-methyl-D-glucoses in a 6:6:3:1 molar ratio.

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