Structural analyses of the HG-type pectin from notopterygium incisum and its effects on galectins

Abstract

In the manuscript, water-soluble polysaccharides WPNI was extracted from notopterygium incisum roots and separated into two homogeneous fractions WPNI-A-a and WPNI-A-b. WPNI-A-a was an arabinogalactan (AG). WPNI-A-b belonged to HG type pectin. The structure of WPNI-A-b was analyzed by FT-IR, NMR, enzymatic hydrolysis (Endo-PG) and UPLC-FLD-MSⁿ. WPNI-A-b was dominated by HG domain, covalently linked with AG and RG-II domains. Oligogalacturonides produced by Endo-PG from HG domain were non-, mono-, di- or tri-methyl esterified with degree of polymerization (DP) from 1 to 6. The distribution of methyl-ester groups was in a block-wise manner. The interaction of WPNI-A-b and its enzymatic hydrolysis products with galectin-1, galectin-3, galectin-7 and galectin-8 showed that AG domain exhibited stronger binding avidity to galectins than RG-II and HG domain, while oligogalacturonides showed no binding activities to galectins. The results would be useful for the application of the pectin from notopterygium incisum.

Keywords: Galectin; Notopterygium incisum; Pectin; Polysaccharides; Structural analysis; UPLC-FLD-MS(n).