title: Structure of a highly substituted beta-xylan of the gum exudate of the palm Livistona chinensis (Chinese fan).
abstract: Structural features of the acidic, highly substituted glycanoxylan (LCP; 87% yield) from the gum exudate of the palm, Livistona chinensis, family Arecaceae, were determined. It had [alpha]D -30 degrees, Mw 1.9x10(5) and a polydispersity ratio Mw/Mn of approximately 1.0. Acid hydrolysis gave rise to Rha, Fuc, Ara, Xyl, and Gal, in a 1:6:46:44:3 molar ratio, and 12% of uronic acid was present. LCP had a highly branched structure with side-chains containing nonreducing end-units (% values are approximate) of Araf (15%), Fucp (4%), Xylp (7%), GlcpA, and 4-Me-GlcpA, and internal 2-O- (5%) and 3-O-substituted Araf (8%), and 2-O-substituted Xylp (14%) units. The (1-->4)-linked beta-Xylp main-chain units of LCP were substituted at O-3 (4%), O-2 (17%), and O-2,3 (16%). Partial acid hydrolysis gave 4-Me-alpha-GlcpA-(1-->2)-[beta-Xylp-(1-->4)](0-2)-Xyl, identified by showing that the uronic acids were single-unit side-chain substituents on O-2. Milder hydrolysis conditions removed from O-3 other side-chains containing Fucp and Araf nonreducing end-units and internal Arap, and 2-O- and 3-O-substituted Araf units. Carboxyl-reduced LCP contained 4-O-methylglucose and glucose in a 3.2:1 molar ratio, arising from GlcpA and 4-OMe-GlcpA nonreducing end-units, respectively. The gum contained small amounts of free alpha-Fucp-(1-->2)-Ara, which corresponds to structures in the polysaccharide. Free myo- and D- or L-chiro-inositol were present in a 9:1 ratio.
authors.affiliation: Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, Caixa Postal 19046, 81531-990 Curitiba, PR, Brazil.
authors.forename: Juliana
authors.initials: J
authors.lastname: Maurer-Menestrina
authors.forename: Guilherme L
authors.initials: GL
authors.lastname: Sassaki
authors.forename: Fernanda F
authors.initials: FF
authors.lastname: Simas
authors.forename: Philip A J
authors.initials: PA
authors.lastname: Gorin
authors.forename: Marcello
authors.initials: M
authors.lastname: Iacomini
mesh_terms: D001089:Arabinose / Q000032:analysis; D028023:Arecaceae / Q000737:chemistry*; D002240:Carbohydrate Sequence; D002965:Classification; D005643:Fucose / Q000032:analysis; D005690:Galactose / Q000032:analysis; D008401:Gas Chromatography-Mass Spectrometry; D005947:Glucose / Q000032:analysis; D005965:Glucuronates / Q000032:analysis; D020723:Glucuronic Acid / Q000032:analysis; D006868:Hydrolysis; D007294:Inositol / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D008969:Molecular Sequence Data; D008970:Molecular Weight; D025942:Oligosaccharides, Branched-Chain / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry* / Q000302:isolation & purification; D012210:Rhamnose / Q000032:analysis; D012542:Scattering, Radiation; D021241:Spectrometry, Mass, Electrospray Ionization; D014574:Uronic Acids / Q000032:analysis; D014990:Xylans / Q000032:analysis / Q000737:chemistry* / Q000145:classification / Q000302:isolation & purification; D014994:Xylose / Q000032:analysis
chemical_list: D005965:Glucuronates; D025942:Oligosaccharides, Branched-Chain; D011134:Polysaccharides; D014574:Uronic Acids; D014990:Xylans; C036035:4-O-methylglucuronic acid; D005643:Fucose; D007294:Inositol; D020723:Glucuronic Acid; C074948:(1-4)-xylan; D014994:Xylose; D001089:Arabinose; D005947:Glucose; D012210:Rhamnose; D005690:Galactose