The structure, conformation, and hypoglycemic activity of a novel heteropolysaccharide from the blackberry fruit.

A homogeneous pectin polysaccharide fraction (BBP-3) with relative molecular weight of 145.1 KDa was isolated from blackberry fruits. The BBP-3 was mainly composed of arabinose, glucose and galacturonic acid with ratio of 5.30%, 3.60% and 91.10%. Structural analysis showed that BBP-3 possessed 1,6-linked β-D-Glcp, 1, 2, 3, 5 linked α-L-Araf and 1, 4 linked α-D-GalpA backbone with branches substituted at the C-2 and C-5 position of arabinose units which include 1, 2, 3, 4 linked β-D-Glcp, and T-linked β-D-GalpA. The conformation analysis indicated that BBP-3 exhibited a solid sphere structure with uniform distribution in 0.1 M NaCl solution. The BBP-3 exhibited excellent α-glucosidase inhibitory activity with IC50 value of 3.70 mg/mL, which was due to the structure change including α-helix and random coil of α-glucosidase caused by BBP-3.