A flaxseed heteropolysaccharide stimulates immune responses and inhibits hepatitis B virus

A novel heteropolysaccharide defined as FP-1 was enriched from flaxseed hull through hot water extraction (boiling water, 2 h, twice) followed by ion-exchange and size exclusion chromatography. FP-1 is a highly purified heteropolysaccharide with an average molecular weight of 2626 kDa. Its monosaccharide composition includes xylose (35.2%), rhamnose (23.8%), galactose (23.4%), arabinose (10.6%), fucose (4.0%), glucose (2.7%) and man nose (0.3%). Main linkage type of FP-1 backbone includes -> 2)-alpha-L-Rhap-(1 ->, -> 4)-alpha-L-Araf-(1 ->, -> 4)-beta-D-Xylp-(1 ->, -> 3,5)-alpha-LAraf-(1 -> and -> 2)-alpha-D-Xylp-(1 -> FP-1 has a triple-helix conformation, indicating its potential bioactivity. FP-1 could stimulate immune responses through inducing mRNA expression of tumor necrosis factor alpha (TNF-alpha), nitric oxide (NO), and interleukin (IL-6 and IL-12) in murine macrophages. FP-1 also inhibits hepatitis B virus (HBV) through inhibition of surface antigen (HBeAg) and envelope antigen (HBeAg) expression and interfering with HBV DNA replication. These findings suggest that FP-1 could be potentially developed as functional food ingredient, immune stimulant and vaccine adjuvant. (C) 2019 Elsevier B.V. All rights reserved.