The core structure characterization and of ginseng neutral polysaccharide with the immune-enhancing activity

The study aims to clarify the structural domain required for the immune enhancement of ginseng neutral polysaccharide (GPN). GPN was first obtained through water extraction and ion-exchange chromatography from Panax ginseng. GPN was hydrolyzed by α-amylase for 24 h and fractionated through gel permeation chromatography to give two final fragments GPNE-I and GPNE-II, with molecular weight of 8.03 × 104 Da for GPNE-I and 3.15 × 104 Da for respectively. FT-IR, methylation and 1D/2D NMR analysis demonstrated that GPNE-I was a heteropolysaccharide consisting mainly of a glucan domain and type I and II arabinogalactans (AG-I and AG-II). GPNE II was a glucan consisting of (1 → 4)-α-d-Glcp backbone with a substitution at O-6 on every two residues. (1 → 3)-α-d-Glcp and (1 → 6)-α-d-Glcp were located at the branches. In the two fractions, both α- and β-t-Glcp as reductive terminals and →4)-α-Glcp as a non-reducing end were detected. The branching degrees of GPNE-I and GPNE-II were 38.17% and 50.78%, respectively. Immunological experiments revealed that GPNE-I exhibited more effectively stimulated lymphocyte proliferation than GPN and GPNE-II, indicating the former showed potential for immunomodulators applications, indicating that GPNE-I might be the core active domain and necessary for GPN to promote lymphocyte proliferation.