Structure of a heteroxylan of gum exudate of the palm Scheelea phalerata (uricuri).
The polysaccharide isolated from the gum exudate of palm Scheelea phalerata (SPN) was water-insoluble and composed of Fuc, Ara, Xyl, and uronic acid moieties in a 5:34:54:7 molar ratio: 12% of phenolics were also present. A soluble polysaccharide (SPNa) was obtained after alkaline treatment, which contained Fuc, Ara, Xyl and uronic acid in a 7:44:42:7 molar ratio, with only 2% phenolics. SPNa had an M(W) approximately 1.04 x 10(5) g mol(-1) and was almost monodisperse (M(W)/M(N) : 1.25 +/-0.22). It had a branched structure with side chains of 2-O-substituted Xylp (approximately 8%) and 3-O-substituted Araf (12%) units, and a large proportion of nonreducing end-units of Araf (15%), Fucp (10%), Xylp (4%), and Arap (6%). The (1 --> 4)-linked beta-Xylp main-chain units were 3-O- (9%), 2-O- (13%), and 2,3-di-O- (13%) substituted. Its (13)C NMR spectrum contained at least 9 C-1 signals, those at delta 108.6 and 107.7 arising from alpha-Araf units. Others were present at delta 175.4 from C-6 of alpha-GlcpA and delta 15.6 from C-6 of Fucp units. The main chain of SPNa was confirmed by analysis of a Smith-degraded polysaccharide (SPDS): methylation analysis provided a 2,3-Me(2)-Xyl (65%) derivative and its (13)C NMR spectrum showed five main signals typical of a (1 --> 4)-linked beta-Xylp units. Methylation analysis of a carboxy-reduced polysaccharide (SPN-CR) revealed a 2,3,4,6-Me(4)-Glc derivative (4%) arising from nonreducing end-units of GlcpA. Alpha-GlcpA-(1 --> 2)-alphabeta-Xy1p and alpha-GlcpA-(1 --> 2)-beta-Xylp-(1 --> 4)-alphabeta-Xylp were obtained via partial acid hydrolysis of SPN, showing the structure of side-chain substituents on O-2 of the main-chain units.
Simas
Fernanda F
FF
Departamento de Bioquímica, Universidade Federal do Paraná, C.P. 19046, CEP 81531-990 Curitiba, PR, Brazil.
Gorin
Philip A J
PA
Guerrini
Marco
M
Naggi
Annamaria
A
Sassaki
Guilherme L
GL
Delgobo
Cirene L
CL
Iacomini
Marcello
M
D001089:Arabinose / Q000032:analysis; D028023:Arecaceae / Q000737:chemistry*; D005643:Fucose / Q000032:analysis; D005881:Gingiva / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D010946:Plants, Medicinal / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry / Q000302:isolation & purification; D014574:Uronic Acids / Q000032:analysis; D014990:Xylans / Q000032:analysis / Q000737:chemistry* / Q000145:classification / Q000302:isolation & purification; D014994:Xylose / Q000032:analysis
D011134:Polysaccharides; D014574:Uronic Acids; D014990:Xylans; D005643:Fucose; D014994:Xylose; D001089:Arabinose