Glucomannan from the Fibre of Sunn Hemp (Crotalaria juncea LINN)

A glucomannan, isolated by fractionation of the alkali-soluble hemicelluloses of sunn-hemp fibre (crotalaria juncea linn), had [α] -45° and, on hydrolysis, yielded glucose, mannose, and xylose in the molar ratios 1.2:1:0.07. The methylated polysaccharide contained an average of ≈45 hexose residues, whereas the corresponding value for the nitrate derivative was 49. Structural studies showed that the glucomannan has a main chain of (1→4)-linked β-D-glucopyranosyl and -mannopyranosyl residues. The molecule appears to have an average of one branch point, through position 6 of both glucose and mannose residues of the main chain. Both D-glucopyranosyl (87%) and d-mannopyranosyl (13%) residues were present as non-reducing end groups. D-glucose and d-mannose occur in the chain both as alternate and contiguous units.