Structural Characterization and Immunomodulatory Activities of a Novel Polysaccharide From Sacha Inchi (Plukenetia volubilis L.) Shell

The novel bioactive polysaccharide, Sacha inchi shell polysaccharide-3 (SISP-3), was isolated from the Sacha inchi (Plukenetia volubilis L.) shell using anion exchange and gel filtration chromatography. This neutral polysaccharide fraction, characterized by a triple-helix structure and a molecular weight of 17,684 Da, was successfully isolated. The composition analysis of SISP-3 revealed the presence of Rha, Ara, Gal, Glc, and Fru in molar ratios of 7.2%:41.7%:40.3%:4.1%:6.7%. The dominant glycosidic linkage in SISP-3 was identified as ⟶4)-Galp-(1⟶, accompanied by a complex branching pattern. The results from RAW264.7 cell experiments showed that SISP-3 significantly enhanced cell viability, phagocytosis, and NO production. Additionally, it significantly stimulated the production of cytokines, including TNF-α, IL-1β, and IL-6, in RAW264.7 cells. These findings suggest that SISP-3 serves as an immune active agent with immunomodulatory properties, indicating its potential as a natural immunomodulatory agent for various applications.