Structural elucidation of the main water-soluble polysaccharide from Rubus anatolicus roots

An acidic heteropolysaccharide, RAPS-1, was isolated from the roots of Rubus anatolicus by water extraction (70 °C) and purification using DEAE-cellulose A52 and Sephadex G-100 column chromatography. The total sugar content and specific optical rotation of RAPS-1 were 96.3% and +196°, respectively. RAPS-1 had a molecular weight of 7900 Da, and was composed of glucose, galactose, and glucuronic acid with a relative molar ratio of 6.2: 1.0: 1.2. Structural features of RAPS-1 were elucidated by a combination of partial acid hydrolysis, periodate oxidation and Smith degradation, methylation, GC-MS, FTIR, and NMR (13C and 1H) analysis. The results indicated that RAPS-1 had a backbone of →4)-α-d-Glcp-(1→ residues, with branches attached to O-6 by α-d-Galp-(1→ and by α-d-GlcAp-(1→.