Molecular dimensions and structural features of neutral polysaccharides from the seed mucilage of Hyptis suaveolens L.

Abstract The seed mucilage of Hyptis suaveolens L. includes acid – and neutral heteropolysaccharides in a ratio of about 1:1. The anionic charged fraction responsible for swelling and viscous behaviour possesses an average molar mass of Mw = 350 kg/mol, Mn = 255 kg/mol. The neutral polysaccharide fraction shows an average molar mass of Mw = 47 kg/mol and Mn = 28 kg/mol and is composed of d -Gal p- , d -Glc p- and d -Man p residues in a molar ratio of about 3:2:1. The structural features present galactoglucan (30%) and galactoglucomannan (70%) with a high level of terminal β-linked d -Gal p residues (18%). Structural details of galactoglucomannan are derived by combined enzymatic and chemical methods as well as NMR spectroscopy. Sequences of octa/nonasaccharide β- d -Glc p -(1 → 4)[β- d -Gal p -(1 → 2)-α- d -Gal p -(1 → 6)]-β- d -Man p -(1 → 4)-β- d -Glc p -(1 → 4)-β- d -Glc p -(1 → 4)[β- d -Gal p -(1 → 2)-α- d -Gal p -(1 → 6)]-β- d -Man p and lower mass tetrasaccharide repeating units β- d -Glc p -(1 → 4)[β- d -Gal p -(1 → 2)-α- d -Gal p -(1 → 6)]-β- d -Man p were found. The level of the prebiotic activity is related to the availability of β-linked d -Gal p residues in the side chains of the molecules.