The gum exudate of Encephalartos friderici-guilielmi.
Studies of the structure of the polysaccharide gum exudate from Encephalartos friderici-guilielmi (a Cycad) confirmed its resemblance to those from other species of the same genus. Partial acid hydrolysis gave numerous products which showed a strong correlation with those from E. longifolius gum. The course of sequential Smith degradations was monitored by analysis of the molecular weights and composition of the products. The mild acid-hydrolysis step of the Smith degradation proceeded in two stages, the second being very slow but yielding a (1-->3)-D-galactan with < 20% of other residues (D-mannose, and some L-arabinose and L-rhamnose). A tentative formulation of the gum shows L-rhamnose and D-glucuronic acid residues exterior to a branched D-galactan framework; these structures are 3-linked to D-mannose, through D-galactopyranosyl or possibly L-arabinopyranosyl residues, within mannoglucuronoglycan chains. Other units occupy O-4 of D-mannose.
Vogt
D C
DC
Department of Chemistry, University of Cape Town, South Africa.
Stephen
A M
AM
D001089:Arabinose / Q000737:chemistry; D002240:Carbohydrate Sequence; D002850:Chromatography, Gel; D005685:Galactans / Q000737:chemistry; D005690:Galactose / Q000737:chemistry; D005944:Glucosamine / Q000737:chemistry; D006868:Hydrolysis; D008969:Molecular Sequence Data; D010944:Plants / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry*
D005685:Galactans; D011134:Polysaccharides; D001089:Arabinose; D005944:Glucosamine; D005690:Galactose