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Characterization of cell wall polysaccharides from Sicana odorifera fruit and structural analysis of a galactan-rich fraction pectins as side chains

Kienteka, Samantha Sharol, Corrêa-Ferreira, Marília Locatelli, de Oliveira Petkowicz, Carmen Lúcia
Carbohydrate polymers 2018 v.197 pp. 395-402
Sicana odorifera, cell walls, citric acid, fruits, galactans, galactose, glucose, light scattering, mannans, mannose, methylation, molecular weight, nuclear magnetic resonance spectroscopy, pectins, polymers, pulp, sodium hydroxide, xyloglucans, xylose
Sicana odorifera is a Brazilian native fruit. In this work, cell wall polysaccharides from S. odorifera pulp were isolated by sequential extraction with water, citric acid, and sodium hydroxide solutions. The monosaccharide composition of crude polysaccharide fractions was determined. The aqueous fractions displayed the highest yields and they were constituted by pectins, having mainly galactans as side chains. The citric acid fraction (SCA) had galactose as the main component. The hemicellulosic fractions consisted mainly of xylose, mannose, galactose, and glucose, suggesting the presence of xyloglucans, xylans and mannans. The SCA fraction was further purified, resulting in a linear galactan (SCAI2). NMR and methylation analysis showed that SCAI2 was a β-(1→4) d-galactan with molar mass of 17,560 g/mol, determined by light scattering. The presence of a linear galactan in free form in fruits is unusual because these polymers usually occur as side chains of type I rhamnogalacturonans.