Abstract
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 mannose (0.3%). Main linkage type of FP-1 backbone includes →2)-α-L-Rhap-(1→, →4)-α-D-GalpA-(1→, →4)-β-D-Xylp-(1→, →3,5)-α-L-Araf-(1→, and →2)-α-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 α (TNF-α), 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 (HBsAg) 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.
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Key Points
Attention has been focused on flaxseed polysaccharides due to their potential broad-spectrum activity and minimal side effects. Macrophages can directly engulf microorganisms and cancer cells, as well as release some immunocytokines including tumor necrosis factors, interleukin and nitric oxide Triple-helix polysaccharides induce greater immunomodulatory responses than other polysaccharides. Hepatitis B virus (HBV) is a major risk factor of hepatocirrhosis and subsequent hepatocellular carcinoma. In this study, a novel heteropolysaccharide FP-1 was isolated and purified from flaxseed. Subsequently, the physicochemical properties of FP-1 were investigated by chemical and instrumental analyses. Its immunomodulatory activity and antiproliferative activity against HBV were investigated using murine RAW264.7 and HepG2.2. A novel heteropolysaccharide (FP-1) with triple-helix conformation was extracted and purified from flaxseed. FP-1 with an average molecular weight of 2626 kDa is consisted of 7 different monosaccharides that linked by primary backbones of →2)-α-L-Rhap-(1 → 4)-α- D-Galp-(1 → and →4)-β-D-Xylp-(1 → 3,5)-α-L-Araf-(1 → 2)-α-D-Xylp-(1 → 4)-β-D-Xylp-(1→. FP-1 possesses significant immunomodulation activity by stimulating the production of macrophage NO, TNF-α, IL-6, and IL-12. In addition, FP-1 exhibits excellent anti-HBV activity by suppressing the secretion of HBV antigens and HBV-DNA replication. FP-1 could be regarded as a promising candidate for anti-HBV agent and immunomodulator.