Purification and characterization of a novel polysaccharide–peptide complex from Clinacanthus nutans Lindau leaves

• A novel polysaccharide CNP-1-2 was purified from C. nutans leaves.
• CNP-1-2 exhibited activity of inhibiting SGC-7901 and stimulating macrophages.
• CNP-1-2 consisted of rhamnose, arabinose, mannose, glucose and galactose.
• CNP-1-2 had the branched and entangled structure.

A novel polysaccharide–peptide complex CNP-1-2 with molecular weight of 9.17 × 104 Da was obtained from Clinacanthus nutans Lindau leaves by hot water extraction, ethanol precipitation, and purification with Superdex 200 and DEAE-Sepharose Fast Flow column chromatography. CNP-1-2 exhibited the highest growth inhibitory effect on human gastric cancer cells SGC-7901 with inhibition ratio of 92.34% and stimulated activation of macrophages with NO secretion level of 47.53 μmol/L among the polysaccharide fractions. CNP-1-2 comprised approximately 87.25% carbohydrate and 9.37% protein. Monosaccharide analysis suggested that CNP-1-2 was composed of l-rhamnose, l-arabinose, d-mannose, d-glucose and d-galactose with a molar ratio of 1.30:1.00:2.56:4.95:5.09. Methylation analysis, FT-IR, and 1H NMR spectroscopy analysis revealed that CNP-1-2 might have a backbone consisting of 1,4-linked Glcp, 1,3-linked Glcp, 1,3-linked Manp, 1,4-linked Galp, 1,2,6-linked Galp and 1,2,6-linked Galp. Its side chain might be composed of 1-linked Araf, 1,6-linked Galp and 1-linked Rhap residues. AFM (atomic force micrograph) analysis revealed that CNP-1-2 had the molecular aggregation along with branched and entangled structure.