A new polysaccharide from a traditional Nigerian plant food: Detarium senegalense Gmelin

The seed flour of an African leguminous plant, Detarium senegalense Gmelin, is used traditionally in Nigeria as a thickening agent in foods. Recent studies have shown that the detarium seed contains a large amount of water-soluble, non-starch polysaccharide (s-NSP), which suggests it has important nutritional properties. The aims of the present study were to characterise the structure and solution properties of purified s-NSP. The main monosaccharide residues of the extracted s-NSP were glucose, xylose, and galactose in the ratio of 1.39:1.00:0.52, suggesting structural similarity to the xyloglucan group of cell wall storage polysaccharides. This was confirmed by comparing the oligosaccharides released on endo-(1 → 4)-β-d-glucanase digestion with those obtained from tamarind seed xyloglucan. The intrinsic viscosity [η] of a sample of the detarium polysaccharide was found to be 8.9 dl/g, indicating that the sample was of high molecular weight, a result confirmed by light scattering. Histochemical examination of detarium seed using bright field and epifluorescence microscopy showed the presence of xyloglucan in highly thickened cell walls, which were particularly prominent at the cell junctions.