Isolation, structural characterization, and bioactivities of neutral polysaccharides from Zizania latifolia

Abstract

The swollen culm (also known as Jiaobai) of Zizania latifolia is formed by the smut Ustilago esculenta invades the Z. latifolia. The new tissue formed due to the symbiotic relationship has entices the attention of researchers to study its polysaccharide structure along with biological evaluation. Five fractions of polysaccharides were obtained owing to hot water extraction, alcoholic precipitation, and chromatographic purification. Bioactivity assays showed that ZLPs have good antioxidant, hypoglycemic activities and protective activity against oxidative damage. The ZLP-1 and ZLP-2 were determined to be neutral polysaccharides with high purity, exhibiting propitious bioactivity, consequently they were subjected to indispensable structural characterization. These results showed that ZLP-1 has molecular weight (Mw) of 103 kDa and glucose (Glc) (76.68 %) as the primary monosaccharide; the ZLP-2 has Mw of 122 kDa and galactose (Gal) (41.04 %) and arabinose (Ara) (27.12 %). Structural elucidation by methylation and nuclear magnetic resonance (NMR) analysis suggested ZLP-1 is a glucan, with →3)-β-Glcp-(1→3)-β-Glcp-(1→4)-β-Glcp-(1→4)-β-Glcp-(1→3,6)-β-Galp-(1→3)-β-Glcp-(1→ as the mainchain and the terminal Araf and Glcp; the ZLP-2 is a Galactoxylan, with →3,4)-β-xylp-(1→3)-β-Galp-(1→3,6)-β-Galp-(1→3,6)-β-Galp-(1→ as the mainchain and the terminal Araf and Glcp. The structural arrangements provide a chemical basis for understanding the nutritional and pharmacological activities of polysaccharides from Zizania latifolia.