A new water-soluble polysaccharide from Echinops pungens Trautv roots. Part I. Isolation, purification, characterization and antioxidant activity

Abstract

EPPS, a new heteropolysaccharide from Echinops pungens roots, was extracted by warm water (70 °C) and fortuitously purified using column chromatographies on DEAE-cellulose A52 and Sephadex G-100. Total carbohydrate content, specific optical rotation and molecular mass of EPPS were 98.3%, -88.2 and 65.7 kDa, respectively. GLC analysis revealed that EPPS was a neutral polysaccharide and contained Gal, Glc, Man, Xyl, and Ara at ratios of 0.96: 5.23:1.00:2.06:1.04. Multiple chemical and instrumental analysis methods such as methylation, periodate oxidation and Smith degradation, partial acid hydrolysis, GLC-MS, FT-IR and NMR (¹H and ¹³C) were employed to elucidate the structure of EPPS and their results showed that its backbone consists of →6)-β-D-Glcp-(1 → residues, with branches attached to O-4 (~38%) by →4)-β-L-Arap-(1→, →4)-β-D-Manp-(1→, →4)-β-D-Xylp-(1→, β-D-Xylp-(1 → and α-D-Galp-(1 → residues. DPPH radical scavenging ability of EPPS was lower than ascorbic acid at identical concentrations and its EC₅₀ value was 1.91 mg/ml.

Keywords: Antioxidant activity; Echinops pungens; Extraction and purification; Polysaccharide; Structural analysis.