An acidic heteropolysaccharide from the flowers of Malva mauritiana L.

An acidic heteropolysaccharide composed of L-rhamnose, D-galactose, L-arabinose, D-xylose, and uronic acids in 1.0:0.5:0.1:0.1:1.8 mole proportion was isolated from the flowers of M. mauritiana L. Structural studies of the polysaccharide involved compositional and methylation analyses of the intact and carboxyl-reduced polymers, graded acid hydrolysis as well as H-1 and C-13 NMR spectroscopy. The results of chemical and spectroscopic analyses indicated a branched structure with the backbone made up of alternating sequences of 2- and 4-linked rhamnogalacturonan-type units with linear segments (DP = 2, 4, 12), segments bearing on O-3 of D-GalA monomeric D-GlcA randomly distributed along the chain (DP = 7, 10, 19, 31), and segments having each D-GalA substituted (DP = 15). Moreover, the results of methylation analysis indicated that about 28% of L-rhamnose residues were branched through O-4.