Isolation and structural characterization of a novel oligosaccharide from the rhamnogalacturonan of Gossypium hirsutum L.

An alkali extract of cell walls of Gossypium hirsutum L. was sequentially digested by endo-polygalacturonase (EC 3.2.1.15), arabinofuranosidase AN1571.2 (EC 3.2.1.55), endo-arabinase (EC 3.2.1.99), and rhamnogalacturonan hydrolase AN9314.2 (EC 3.2.1.15). The rhamnogalacturonan hydrolase-generated oligosaccharides were separated by ultrafiltration, size-exclusion, and anion exchange chromatography. Fractions from the anion exchange chromatography were pooled, lyophilized, and screened by MALDI-TOFMS. A new oligosaccharide (RGS29), which contained a rhamnogalacturonan dimer backbone with two galactose and two arabinose residues in the side chains, was found. Its structure was identified by 1D and 2D NMR spectra as follows: [GRAPHICS] (c) 2008 Elsevier Ltd. All rights reserved.