Physicochemical Characterization And Prebiotic Effect Of Water Soluble Polysaccharides Extracted From Medicinal Plant: Astragalus Armatus Lam. (fabaceae)

Résumé: Astragalus armatus Lam. (Fabaceae), a spontaneous plant used as a traditional medicine in Ghardaïa (Septentrional Sahara Algerian). This paper reports the Physico-chemical characterization and prebiotic effect of water soluble polysaccharides from A.armatus seeds. These polysaccharides were obtained by elimination of the ethanol extract and sequential extraction in distilled water, followed by precipitation in 75% isopropanol. The yield of extract is 7.0% (w/w). The crude water soluble polysaccharide extracts were further characterized and revealed the average values 5.23±0.88% ashes, 11.93±1.76% proteins and 79.93±3.66% carbohydrates, among them 20.87±1.26% are uronic acid and 61.35±2.13% are neutral monosaccharides. A single hydrolytic step with 4M TFA at 80°C for 1 h is suggested to be more effective in releasing monomers from polysaccharides than other hydrolysis procedures.The identification of monosaccharide composition by high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) method shows 48.76% of galactose, 15.42% of arabinose, 11.27% of rhamnose and 18.61% of galacturonic acid. Partial hydrolysis of water-soluble polysaccharides was found to have a growth stimulatory effect on Lactobacillus acidophilus and Lactobacillus bulgaricus less than that of fructo-oligosaccharide (RP95). However, the hydrolyzate has no effect on the Escherichia coli strain. The present study shows that partial hydrolyzate of water-soluble polysaccharides stimulates the growth of Lactobacillus acidophilus and Lactobacillus bulgaricus bacteria, and that partial hydrolyzate of water-soluble polysaccharides has potential use as a prebiotic health–food.

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