An acidic heteropolysaccharide rich in galactose and arabinose derived from ginger: Structure and dynamics

Polysaccharide is one of the most important constituents of ginger, exhibiting extensive bioactivities. However, the structures of ginger polysaccharides are poorly understood and remain to be explored. In this study, a polysaccharide UGP1 was isolated from ginger and then a series of chemical, spectroscopic, chromatographic and thermal methods were applied to determine the properties and structure of it. In addition, the digestion and fecal fermentation processes of UGP1 were also investigated. Results showed that the saccharide content of UGP1 was 91.11% ± 0.42% and UGP1 was revealed to be an acidic heteropolysaccharide with helix structure comprised of six kinds of monosaccharide, including galactose, arabinose, rhamnose, glucose, mannose and glucuronic acid, among which galactose (29.32%) and arabinose (19.55%) accounted for the highest proportion. Specifically, in the backbone of UGP1 existed the →4)-α-D-GlcpA-(1→, →3)-α-L-Rhap-(1→, →4,6)-β-D-Galp-(1→, →6)-β-D-Galp-(1→, →3,6)-β-D-Manp-(1→ and →3)-β-D-Glcp-(1→ residues and in the branch chains of UGP1 located the α-L-Araf-(1→ and α-D-Glcp-(1→ residues. Besides, UGP1 was almost not digested by saliva and gastrointestinal tract but could be fermented by gut microbiota into short chain fatty acids (SCFA), containing acetic acid, propionic acid, n-valeric acid and a bit of i-butyric acid and n-butyric acid, which might mediate the interactions between gut microbiota and organisms and thus regulate the health of the human body. The current study reveals the structure of another ginger polysaccharide and helps understand its physiological process, lays the structural foundation of its activities and provides possibility for developing UGP1 into a novel prebiotic.