An Acidic Polysaccharide Isolated from the Midrib of Leaves of Nicotiana tabacum

Abstract

An acidic polysaccharide (APS-H) purified from the hemicellulosic fraction of the midrib of Nicotiana tabacum was composed of D-galacturonic acid, L-rhamnose, L-arabinose and D-galactose in a molar ratio of 31.8:15.4:9.9:42.9. Its molecular weight was estimated to be 90, 000 by gel filtration chromatography. APS-H had a pectin-like structure in which the rhamnogalacturonan backbone was composed of (1→2)-linked L-rhamnopyranosyl and (1→4)-linked D-galacturonosyl residues in a ratio of approximately 1:2.1. It also contained (1→4)-linked D-galactan and (1→5)-linked L-arabinofuranosyl moieties as the side chains. Branch points occurred mainly at C-4 of (1→2)-linked L-rhamnosyl residues in the backbone and at C-6 of (l→4)-linked D-galactosyl residues in the side chains.