Structural characterization of a new water-soluble polysaccharide isolated from Acanthophyllum acerosum roots and its antioxidant activity.

A new water-soluble polysaccharide named as AAPS-1, was extracted with warm water from the roots of Acanthophyllum acerosum and further purified by DEAE-cellulose A52 anion-exchange and Sephadex G-50 gel filtration chromatography. AAPS-1 was a neutral polysaccharide, with a molecular weight of 23.2kDa and a specific optical rotation of +181.3° (c 1.0, H2O), and comprised of Glucose, Galactose and Arabinose with a relative molar ratio of 1.6:5.1:1.0. Structure features of AAPS-1 were investigated by a combination of chemical and instrumental analysis, such as partial acid hydrolysis, methylation, periodate oxidation and Smith degradation, GC-MS, FTIR and NMR (13C and 1H). The data obtained indicate that AAPS-1 possessed a backbone of →6)-α-d-Galp-(1→ residues, with branches attached to O-2 (∼35%) by α-d-Glcp-(1→ and at O-3 (∼16%) by α-d-Galp-(1→ and by β-l-Arap-(1→3)-β-l-Arap-(1→3)-β-l-Arap-(1→. The scavenging activity of AAPS-1 against DPPH radical was less than that of ascorbic acid at the same concentrations and the EC50 value of AAPS-1 was 1.4mg/ml.