Structure characterization and hypoglycemic activity of an arabinogalactan from Phyllostachys heterocycla bamboo...

An arabinogalactan (PBSS2) was fractionated from the bamboo shoot shell of Phyllostachys heterocycla. Structural analysis indicated that PBSS2 was mainly composed of galactose, arabinose, xylose and galacturonic acid in a ratio of 7.8:6.3:1.4:1.0. It was a 1,3- linked β-d-galactan having 61.1% degree of branching at the O-6 positions. The three branches consisting of 1,4-linked β-d-Xylp terminated with β-d-Galp, 1,5-linked α-L-Araf inserted with 1,4-α-6-O-Me-d-GalpA and 1,3,5-linked α-L-Araf terminated by α-L-Araf. Furthermore, its chain conformation on the values of weight-average molecular weight (M_w), the radius of gyration (R_g) and intrinsic viscosity ([η]) were found as following: 7.36 × 10⁴ g/mol, 12.8 nm and 17.7 mL/g, which was evidenced by AFM. The structure exponent of α (0.38) and d_f (2.17) revealed it existed as a sphere-like chain in NaNO₃ aqueous solution. In vitro Caco-2 cells assay showed that PBSS2 presented positive effect on the inhibition of glucose absorption in time-dependent manner at relatively high concentration.