Polysaccharide composition ofPolygonum aviculare
A polysaccharide isolated from the epigeal parts ofPolygonum aviculare has been fractionated. It has been shown that the initial polysaccharide consists of at least four fractions differing in their monosaccharide compositions and physico-mechanical properties.
FRACTIONATION OF PECTINS FROM SUNFLOWERS, SUGAR BEETS, APPLES, AND CITRUS FRUITS
Pectins from sunflower heads, sugar beet, apple, and citrus fruits were separated into acid-insoluble pectic acids and acid-soluble polysaccharides. The acid-soluble polysaccharides were shown by m...
THE ACID HYDROLYSIS OF GLYCOSIDES: II. EFFECT OF SUBSTITUENTS AT C-5
First-order rate coefficients at three temperatures, and energies and entropies of activation, have been determined for the acid-catalyzed hydrolysis of methyl glucopyranosides containing various substituents at C-5 and for glycopyranosiduronic acids with different aglycones. Substitution at C-5 increased the stability towards acids of methyl α- and β-D-glucopyranosides, but there was no correlation between either the polarity or the size of the substituent and the rates of hydrolysis. The operation of either an inductive or a conformational effect alone was accordingly deemed unlikely.Methyl α- and β-D-glucopyranosiduronic acids and methyl α-D-galactopyranosiduronic acid were only slightly more stable towards acids than the glycoside analogs, while benzyl β-D-glucopyranosiduronic acid was three times more stable. The presence of a methyl ester group at the carboxyl function increased the stability of the glycuronide bond. Isopropyl, n-butyl, isobutyl, and neopentyl β-D-glucopyranosiduronic acids were hyd...