Structure characterization of a novel polysaccharide from Chinese wild fruits (Passiflora foetida) and its immune-enhancing activity

A novel polysaccharide (PFP1) with an average molecular weight of 2.02 x 10(5) g/mol was isolated from Passiflora foetida fruits through hot water extraction, ethanol precipitation and column chromatography. The structure of PFP1 was determined by GPC-MALS-Rl, IC, FT-IR, GC-MS and NMR. The structural analysis showed that PFP1 was a heteropolysaccharide and composed of mannose (48.83%), galactose (32.46%), glucose (6.21%), arabinose (5.88%), fructose (2.24%), galacturonic acid (2.20%), xylose (1.17%), fucose (0.17%), ribose (0.05%), and glucuronic acid (0.78%), with a backbone structure of->1)-alpha-D-Manp->1,2)-beta-D-Manp-linked 1,2,6)-beta-D-Manp residues and side chains consisted of-1)-beta-D-Galp,-> 1,4)-alpha-D-Manp and -> 1,3)-beta-D-Galp, -> 1,3)-alpha-D-Galp, -> 1, 6)-beta-D-Manp, -> 1, 6)-beta-D-Galp, -> 1,2,3)-beta residues. The results of immune-enhancing assays revealed that PFP1 could obviously promote the production of NO and secretion of cytokines (TNF-alpha and IL-6) of macrophage RAW264.7. These findings demonstrate that P. foetida fruit polysaccharides can be utilized as a potential immune-enhancing functional food. (C) 2019 Published by Elsevier B.V.