Structure elucidation and immunomodulatory activity in vitro of a xylan from roots of Cudrania tricuspidata

To discover new immunomodulator in the food industry, a water-soluble polysaccharide, CTPB1 was obtained from roots of Cudrania tricuspidata (Carr.) Bur. The average molecular weight of this polysaccharide was estimated to be 4.0 × 104 Da. Monosaccharide composition analysis indicated that the only neutral sugar present in this polysaccharide was xylose. From methylation analysis and 1H and 13C NMR spectroscopy, the structure of CTPB1 was deduced to be (4-O-methyl-d-glucurono)-d-xylan, with the 4-O-methyl-d-glucopyranosyluronic acid group linked to O-2 of a (1 → 4)-β-d-xylan. The repeating unit of CTPB1 is composed of one non-reducing terminal residue of 4-O-methyl-d-glucuronic acid on every four xylose residues. Immunomodulatory activity assays in vitro showed that CTPB1 may induce the proliferation of mouse splenocytes. It was suggested that CTPB1 could be a potential immunostimulant used in the food industry.