Plant mucilages. XXIX. Isolation and characterization of a mucous polysaccharide, "plantago-mucilage A", from the seeds of Plantago major var. asiatica

A representative mucous polysaccharide, named Plantago-mucilage A, was isolated from the seeds of Plantago major L. var. asiatica DECAISNE (=Plantago asiatica L.). The final preparation was homogeneous as determined by ultracentrifugal analysis, glass-fiber electrophoresis, and gel chromatography. It was readily soluble in water and its solution gave an intrinsic viscosity value of 39.5. It was composed of L-arabinose, D-xylose, D-glucuronic acid, and D-galacturonic acid in the molar ratio of 4.0 : 10.8 : 3.3 : 0.7, and its molecular weight was estimated to be about 1500000. O-Acetyl groups were identified in it and their content amounted to be 4.8%. Reduction of carboxyl groups, methylation analysis, controlled Smith degradation, and partial acid hydrolysis studies showed that the mucilage possesses a main chain composed of β-1→4 linked D-xylopyranose residues having other D-xylopyranose side chains at position 3 and branches composed of O-α-(D-glucopyranosyluronic acid)-(1→3)-α-L-arabinofuranose and of O-α-(D-galactopyranosyluronic acid)-(1→3)-α-L-arabinofuranose at position 2 of the residual D-xylopyranose units.