Structural characterization and immune-modulating properties of a novel β-galactomannan extracted from black soybean hulls.

Galactomannan soluble in water (BBHW) was extracted from black soybean hulls through acid-assisted extraction and column chromatography and its immune-modulating capacity and features of the structure were elucidated. BBHW had an average molecular mass of 134,194 Da and was made up of mannose, galactose, glucose, and arabinose in a molar ratio of 1.40:1.0:0.14:0.03. The backbone structure of BBHW were primarily composed of →4)-β-D-Manp-(1 → and →4,6)-β-D-Manp-(1→, branched with α-D-Galp-(1→, α-D-Galp-(1 → 6)-α-D-Glcp-(1→, and α-L-Araf-(1 → at O-6. Further examination of BBHW's molecular chains disclosed a conformation consisting of a stacked macromolecular network and a triple-helix configuration. In vitro assays demonstrated that BBHW (50-400 μg/mL) significantly improved immunological responses in RAW264.7 macrophages by increasing phagocytosis and boosting NO and cytokine release via MAPK and NF-κB signaling. These findings indicate that BBHW holds considerable potential as an immunomodulatory agent, with applications in the food and pharmaceutical industries.