ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Distribution pattern of 4-o-methyl-d-glucuronic acid units in 4-o-methyl-d-glucurono-d-xylan isolated from the leaves of marsh mallow (Althaea officinalis l, var rhobusta

A. Kardošová, A. Malovíková, J. Rosík, and P. Capek

Institute of Chemistry, Centre for Chemical Research, Slovak Academy of Sciences, CS-84238 Bratislava

Abstract: A homogeneous, water-soluble 4-O-methyl-D-glucurono-D-xylan has been isolated from the leaves of marsh mallow. The mole ratio of D-xylose and 4-O-methyl-D-glucuronic acid was 7 : 1 . The main chain was built of (1 -•4)-linked ß-D-xylopyranosyl residues and 4-O-methyl-D-glucuronic acid was attached as single terminal units to 0-2 of D-xylose. The single-ion activity coefficient of calcium counterions γ_Ca2+ was estimated in a molecular disperse solution of the polysaccharide. The mean distance of adjacent carboxyl groups, b = 4.00 nm, was obtained from experimentally determined value γ_Ca2+ = 0.712, using the relation γ_Ca2+=f(b). From comparison of the b value with the length of the D-xylose unit (0.52 nm) it follows that the uronic acid units are apart and distributed regularly along the macromolecule chain, i.e. approximately each seventh D-xylose unit is substituted by 4-O-methyl-D-glucuronic acid.

Full paper in Portable Document Format: 441a111.pdf

Chemical Papers 44 (1) 111–117 (1990)