Structural and biological features of a hydrogel from seed coats of Chorisia speciosa

Seed coats from Chorisia speciosa form a hydrogel on contact with water. When the hydrogel was solubilized and the solution centrifuged, subsequent ethanol precipitation gave a polysaccharide (F-I) composed of rhamnose, galactose and uronic acid in a molar ratio of 25:44:31. Analysis of F-I by HPSEC-MALLS showed a homogenous polymer with high molecular weight. It consisted of a main chain of (1-->4)-linked beta-galactopyranosyl units as indicated by NMR spectral and methylation data analysis, with rhamnose, galactose and glucuronic acid as non-reducing end units. This fraction interfered with adhesion of Colletotrichum graminicola, a causal agent of anthracnose, to polystyrene slides and to leaves of corn, thus delaying infection in the latter.