Isolation and characteristics of polysaccharide from Amorphophallus corrugatus in Vietnam

A polysaccharide has been isolated from the tuber of Amorphophallus corrugatus (one of the most abundant Amorphophallus species in Vietnam forests). The chemical structure, molecular weight, moisture uptake and degree of crystallization of polysaccharide were investigated by nuclear magnetic resonance spectroscopy (NMR), viscosimetry, differential scanning calorimetry (DSC) and X-ray diffraction. The results shown that the polysaccharide was a glucomannan with a backbone of (1,4)-linked β-d-mannopyranosyl residues and β-d-glucopyranosyl residues, and was demonstrated to be composed of d-mannose and d-glucose in 2.25/1.0 molar ratio and having a relatively low degree of branching at C6 positions of the hexose residues. The degree of acetylation was about 7.57% and the acetyl group might attach to glucose and mannose residues at positions C2, C3, and C6. The molecular weight of glucomannan was Mv = 1.57 × 106 Da. The polysaccharide was amorphous and the moisture uptake was about 8.37%.