A polysaccharide TKP-2-1 from Tamarindus indica L: Purification, structural characterization and immunomodulating activity

Abstract

Abstract Herein, TKP-2-1, a water-soluble polysaccharide with a weight-average molecular weight of 1693 kDa, was isolated from the seed kernels of Tamarindus indica L. UV, FT-IR, GC–MS and 1D, 2D-NMR data analysis revealed that TKP-2-1 is chiefly composed of a (1 → 4)-β-D-glucan backbone with side chains of α-D-xylopyranosyl, α-D-xylopyranosyl-(1 → 4)-β-D-galactopyranosyl and β-D-galactopyranosyl-(1 → 2)-α-D-xylopyranosyl sugar moieties linked to the C-6 positions of the glucose residues. Furthermore, TKP-2-1 exhibited a potent immunostimulatory activity through enhancing phagocytosis and NO production, as well as the expression of iNOS, IL-1β, IL-6, and TNF-α in RAW264.7 macrophages. Mechanistically, TKP-2-1 caused the degradation of IκBα and nuclear translocation of NF-κB p65, and phosphorylation of ERK, JNK and p38 MAPK in RAW264.7 cells. Specific inhibitors of NF-κB, ERK, JNK, and p38 MAPK obviously abolished TKP-2-1-induced NO production in RAW264.7 cells, respectively. Thus, TKP-2-1 from the seed kernels of T. indica might potentially be used as a natural immunomodulator in functional foods.