Structure of chia seed polysaccharide exudate

Chia seed gum varies in molecular weight from 0·8 to 2·0 × 106 daltons, as determined by gel filtration. β-d-Xylose, α-d-glucose, and 4-O-methyl-α-d-glucuronic acid were obtained on hydrolysis in the respective ratios of 2:1:1. An aldobiouronic acid, 2-O-(4-O-methyl-α-d-glucopyranosiduronic acid)-d-xylose, was obtained by partial hydrolysis. A tentative structural unit proposed for the polysaccharide is a tetrasaccharide with 4-O-methyl-α-d-glucoronopyranosyl residues occurring as branches at O-2 of some β-d-xylopyranosyl residues in the main chain consisting of (1→4)-β-d-xylopyranosyl-(1→4)-α-d-glucopyranosyl-(1→4)-β-d-xylopyranosyl units. A linear tetrasaccharide was characterized that incorporates these structural features.