Structural characterization and immunomodulating activities of a novel polysaccharide from Nervilia fordii

Nervilia fordii (Hance) Schltr. has been widely used as a medicinal and edible herb in South-west China and Southeast Asia. In this study, NFP-1, a new water-soluble polysaccharidewith a purity of 97.8%, was purified from water extract of Nervilia fordii by DEAE-cellulose and Sephadex G-100 chromatography. NFP-1 has a relative molecular weight of 950 kDa determined by high performance gel-permeation chromatography (HPGPC). Its monosaccharide compositions were analyzed by high performance liquid chromatography (HPLC) after pre-column derivatizing its hydrolysate with 1-phenyl-3-methyl-5-pyrazolone (PMP). NFP-1 mainly consists of galactose, arabinose, rhamnose, and galacturonic acid. Based on FT-IR, methylation and GC-MS analysis, and NMR, the structure unit of NFP-1 was established as -> 4)-alpha-Rhap-(2 -> 4)-alpha-GalpA-(1 -> 2)-alpha-Rhap-(1 -> 2)-alpha-Rhap-(4 -> 1)-beta-Galp-T containing two branch chains of -> 2,4)-alpha-Rhap-(1 -> 5)-alpha-Araf-(1 -> 3)-alpha-Araf-(1 ->, and -> 2,4)-alpha-Rhap-(1 -> 4)-beta-Galp-(1 ->. The immunomodulatory assays revealed the dual-functionalities of NFP-1. NFP-1 could significantly induce the secretion of nitric oxide (NO), and promote the secretions of TNF-alpha, IL-6, and IL-1 beta in RAW264.7 macrophages. NFP-1 could also significantly inhibit the production of NO, depress the secretions of TNF-alpha, IL-6 and IL-1 beta in RAW264.7 macrophages activated by lipopolysaccharide (LPS), and promote the production of IL-10 meanwhile. Our study suggested that Nervilia fordii could be an ideal medicinal or functional food due to its dual immunomodulatory activities. (C) 2018 Elsevier B.V. All rights reserved.