title: Chemical structure of the complex pyruvylated and sulfated agaran from the red seaweed Palisada flagellifera (Ceramiales, Rhodophyta).
abstract: A homogeneous agaran fraction from Palisada flagellifera (Laurencia complex, Rhodomelaceae, Ceramiales) was obtained by aqueous room-temperature extraction, followed by ion-exchange chromatography. This galactan presents a highly complex structure with at least 18 different types of derivatives. The A units were found mostly pyruvylated, 2-sulfated (∼34%), and 6-methylated (∼34%), with the latter partially 2- and 2,4-sulfated. Minor amounts of β-D-galactopyranosyl units 2-, 6- and 2,6-sulfated, 6-glycosylated, and non-substituted are also present. The B-units are L-sugars composed predominantly of their cyclized derivatives, 3,6-anhydrogalactose and 3,6-anhydro-2-O-methylgalactose (∼56%). The former are linked to β-D-galactosyl (6-methyl) (6-glycosylated) units, as well as to 4,6-O-(1-carboxyethylidene)-β-D-galactose 2-sulfate in the proportion of 3:1.8, respectively. A significant amount (∼18%) of the α-L-galactopyranosyl units are linked to pyruvylated β-D-galactose 2-sulfate residues. An important part of the B-units (20%) is represented by α-L-galactose 6-sulfate substituted on C-3 by xylosyl, galactosyl and/or 2,3-di-O-methylgalactose units or sulfate groups that preclude their cyclization to 3,6-anhydrogalactosyl derivative. The precursor units are present in relatively low percentages. Kinetic studies suggest that in P. flagellifera agaran the cyclizable units are linked to 6-O-methyl-β-D-galactosyl and/or β-D-galactosyl units (6-glycosylated). The structural complexity of this polysaccharide is increased by the presence of 2- and 3,6-sulfated α-L-galactoses, with the latter additionally 2-O-methylated. Therefore, the major subfraction obtained from the cold extract contains structurally complex sulfated, methylated, and pyruvylated agaran.
authors: Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, PO Box: 19046, CEP: 81531-990 Curitiba, Paraná, Brazil.
authors: Luciana G
authors: LG
authors: Ferreira
authors: Miguel D
authors: MD
authors: Noseda
authors: Alan G
authors: AG
authors: Gonçalves
authors: Diogo R B
authors: DR
authors: Ducatti
authors: Mutue T
authors: MT
authors: Fujii
authors: Maria E R
authors: ME
authors: Duarte
mesh_terms: D002240:Carbohydrate Sequence; D003500:Cyclization; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000737:chemistry* / Q000302:isolation & purification; D011773:Pyruvates / Q000737:chemistry*; D000461:Rhodophyta / Q000737:chemistry*; D013431:Sulfates / Q000737:chemistry*
chemical_list: D011134:Polysaccharides; D011773:Pyruvates; D013431:Sulfates