e-Polymers 2005, no. 063. ISSN 1618-7229 http://www.e-polymers.org Extraction and characterization of polysaccharides from Mesembryanthemum crystallinum Nour H. M’sakni 1 , Hamouda Zayane 1 , Hatem Majdoub 1 , Claudine Morvan 2 , Sadok Roudesli 1 , André Deratani 3 * 1 Laboratoire Polymères, Biopolymères et Matériaux Organiques, Faculté des Sciences de Monastir, 5019 Monastir, Tunisia 2 Laboratoire de Glycobiologie et de Transport chez les Végétaux, UMR 6037 CNRS, Université de Rouen, 76821 Mont-Saint-Aignan Cedex, France 3 Institut Européen des Membranes, UMR 5635 CNRS-ENSCM-UM II, 2 place Eugène Bataillon, 34095 Montpellier, France; Fax +33 467 149 119; andre.deratani@iemm.univ-montp2.fr (Received: April 11, 2005; published: September 20, 2005) Abstract: Water-soluble polysaccharides were isolated from Mesembryanthemum crystallinum. Two methods were applied, based (i) on the extraction in hot water (for fresh and dry plants, FP and DP) and (ii) on freeze-thawing of fresh plants (FT). Each fraction was purified by precipitation in ethanol followed by ultrafiltration of recovered solids dissolved in water through a membrane with a molecular weight cut off of 100 000. Elemental analysis demonstrated that the extracted products were polysaccharides exempt from proteins. The yield relative to the corresponding dry matter varied from 1.6 to 3% depending on the starting sample and the extraction process. Obtained products were characterised by their structural (sugar composition, degree of methylation (DM) and acetylation, molar mass of acid equivalent unit) and macromolecular characteristics (molar mass and intrinsic viscosity). A galacturonic-acid content larger than 65% and a DM value of c. 40% showed that the isolated polysaccharides belong to the fairly methylated pectin class. FP and FT structures consisted of the two blocks homogalacturonan (HG) and rhamnogalacturonan-I (RG-I) with relative proportions of 62 - 68% and 29 - 34%, respectively. They showed very similar physicochemical behaviour. On the other hand, DP exhibited significant differences in the chemical structure (50% HG and 46% RG-I blocks) and physical properties, indicating that partial degradation of HG moieties occurred during plant drying. Abbreviations AIS; alcohol-insoluble substance. Ara: arabinose. Gal: galactose. GalA: galact- uronic acid. Glu: glucose. Man: mannose. Rha: rhamnose. Xyl: xylose. HG: homogalacturonan. RG-I: rhamnogalacturonan of type I. AEW: molar mass of the acid equivalent unit. FP and DP: polysaccharide extracted, respectively, from fresh and dry plants by hot water. FP P and DP P : the corresponding intermediate precipi- tated fractions. FT: polysaccharide extracted from fresh plants using the freeze-thaw method. FT P : the corresponding intermediate precipitated fraction. DM: degree of methylation. DA: degree of acetylation. 1 Unauthenticated Download Date | 11/9/16 11:25 AM