Polysaccharides mannuronic acid-containing

Polyuronides macromolecular compounds found in plants, consisting of units of uronic acids in the pyr-anose form (see Carbohydrates). The main components are o-glucuronic acid, o-galacturonic acid and D-mannuronic acid. P. contain free carboxyl groups and are consequently more strongly hydrated than polysaccharides formed from neutral monosaccharides. Examples are pectins, alginic acid and plant mucilages. 

A series of polysaccharides have been isolated from the sea grass, Phyllos-padix torreyi, which are unusual in containing residues of o-apiose (2—28 One of these polysaccharides had the composition, L-rhamnose, L-arabinose, D-xylose, D-apiose, D-galactose, and D-mannuronic acid in the molar ratio 4 1 5 2 4 9. Of the D-apiose residues 80 % were oxidized by periodate and the major neutral sugar residues found in the hydrolysate of the methylated polysaccharide were 2,3,5-tri-O-methyl-L-arabinose, 2,5-di-O-methyl-L-arabinose, 3,4-di-O-methyl-L-rhamnose, 2,3-di-O-methyl-D-xylose, 2,3,6-tri-0-methyl-D-galactose, and 2,4-di-O-methyl-D-galactose in the ratio 1 1 6 6 3 3. 

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