No abstract

A glucuronoarabinoxylan (CNAL) was extracted with 1% aq. KOH (25°C) from Cocos nucifera gum exudate. It had a homogeneous profile on HPSEC-MALLS-RI (Mw 4.6 × 10(4)g/mol) and was composed of Fuc, Ara, Xyl, GlcpA (and 4-O-GlcpA) in a 7:28:62:3 molar ratio. Methylation data showed a branched structure with 39% of non-reducing end units, 3-O-substituted Araf (8%), 3,4-di-O- (15%), 2,4-di-O- (5%) and 2,3,4-tri-O-substituted Xylp units (17%). The anomeric region of CNAL (13)C NMR spectrum contained 9 signals, indicating a complex structure. The main chain of CNAL was characterized by analysis of a Smith-degraded polysaccharide. Its (13)C NMR spectrum showed 5 main signals at δ 101.6, δ 75.5, δ 73.9, δ 72.5, and δ 63.1 that were attributed to C-1, C-4, C-3, C-2 and C-5 of (1→4)-linked β-Xylp-main chain units, respectively. CNAL exhibited gastroprotective effect, by reducing gastric hemorrhagic lesions, when orally administered (1 and 3mg/kg) to rats prior to ethanol administration.

Native polysaccharide from pineapple gum (PANP) was obtained following alkaline extraction of gum and fractionation with cetylpyridinium chloride. It was characterized as a glucuronoarabinoxylan using NMR, methylation data, controlled Smith degradation, carboxy-reduction, and ESI-MS of oligosaccharides produced on mild acid hydrolysis of PANP. HSPEC-MALLS-RI of carboxy-reduced fraction showed homogeneous profile (Mw 1.943×10(5) g/mol). PANP was composed of Ara, Xyl, Gal, and GlcpA (40:23:7:30 molar ratio). Its main chain presented (1→4)-linked β-xylan, highly substituted at O-2 and O-3 by side chains of 3-O- and 3,5-di-O-linked α-Araf, 2-O- and 4-O-linked α-GlcpA, and nonreducing end-units of α-Araf, β-Arap, β-Galp, and α-GlcpA. ESI-MS of a mixture of oligosaccharides formed on the mild acid hydrolysis of PANP was consistent with repetitive structures of α-GlcpA O-3 linked at β-Xylp units, whereas in others glucuronoarabinoxylan-type gum exudates, α-GlcpA units had been previously found to be linked at O-2.