Structural characteristic of pectin-glucuronoxylan complex from Dolichos lablab L. hull

Polysaccharides are important constituents in Dolichos lablab hull. Herein, pectin-glucuronoxylan complex from D. lablab hull designated as DLHP-3 ( D. lablab hull polysaccharide,) was prepared by ion exchange and gel permeation chromatography , and further characterized by acid degradation and enzymatic hydrolysis , methylation combined with GC–MS, NMR and MALDI-TOF-MS analysis. Both of pectin and glucuronoxylan regions were found in DLHP-3. The glucuronoxylan region consisted of a →4)-β-Xyl p -(1→ backbone with branches of α-Glc p A-(1→ substituted at O -2 site, and the ratio of xylose to glucuronic acid was about 5:1. Acetyl groups were mainly attached to O -3 site of →2,4)-β-Xyl p -(1→ residues. The main chain of pectin region could be represented by →4)-α-Gal p A-(1→4)-α-Gal p A-(1→ and →2)-α-Rha p -(1→4)-α-Gal p A-(1→ with partial methyl-esterification. The side chains were deduced to embrace arabinan and arabinogalactan linked to rhamnogalacturonan-I region. Pectin was probably covalently bound to glucuronoxylan. Our findings uncovered the molecular structure of pectin-glucuronoxylan complex from D. lablab hull.