Partial acid hydrolysis galactans

An L-arabino-D-galactan, in 2% yield, has been isolated from the fruits of Dillenia indica. From the results of partial acid hydrolysis and methylation analyses, when 2,6-di-O-methyl-D-galactose, 2,3,6-tri-O-methyl-D-galactose, 2,3,4,6-tetra-(9-methyl-D-galactose, and 2,3,5-tri-O-methyl-L-arabinose residues in the molar ratio 7 3 1 8 were identified, it was concluded that the polysaccharide was a (1- 4)-j3-D-galactan that contained L-arabinofuranose residues linked at 0-3 of some of the D-galactose residues in the main chain. 

Finally, the 3-configuration of some of the galactosidic linkages has also been established by chromatographic comparison to known standards of oligosaccharides derived from the galactan by partial acid hydrolysis (96). 

The arabinogalactans are also related to one another in that they all appear to have a galactan backbone with arabinosyl sidechains. The structures of these polysaccharides have been further investigated by partial acid hydrolysis and by periodate oxidation 14, 72, 87, 116). The arabinosyl residues are hydrolyzed preferentially by mild acidic... 

The polyuronides are polysaccharides that yield uronic acid on hydrolysis. The most important of these are the pectins. Pectins are found in most plants, particularly fruits. They are extracted in commercial quantities and used to make jellies and to alter the consistencies of foodstuffs. Citrus pectin is mainly a partially methylated polygalacturonic acid, where the alpha—1,4-galacturonic acid units are present. Other pectins are arabans (polyarabinose) and galactans (polygalactose). 

D-Galactose is obtained from the hydrolysis of lactose, its chief source from raffinose from the galactans of gums and mucilages and from the galactolipides, or cerebrosides, of the central nervous system. It resembles glucose, but is much less sweet, and less soluble in water. It is dextro-rotatoiy, [a] = + 80°. On partial oxidation, it forms the sparingly soluble mucic acid, by which it may be identified. 

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