Structure characterization, antioxidant and hypoglycemic activity of an arabinogalactoglucan from Scutellaria baicalensis Georgi

An arabinogalactoglucan SBP-1 was purified from Scutellaria baicalensis by DEAE-52 and Sephadex G-100 column chromatography. The structure of SBP-1 was characterized using HPLC, IR, GC-MS, 1-D and 2-D NMR. The antioxidant and hypoglycemic activity of SBP-1 was investigated by vitro evaluation. The results showed that SBP-1 was composed of arabinose, glucose and galactose in a molar ratio of 1.0:5.9:1.1 and its Mw were 91,156. The backbone of SBP-1 was mainly composed of repeating →1)-α-D-Glcp-(4 → 1)-α-D-Glcp-(3 → 1)-α-D-Galp-(4→. The braches were composed of →2)-α-L-Araf-(1→, →3)-β-D-Glcp-(1→ and α-D-Glcp-(1→, which mainly substituted at O-6 of Glc, while terminal residue was α-L-Araf-(1→ and α-D-Glcp-(1→. Vitro bioactivity showed that SBP-1 had dose-dependent antioxidant and hypoglycemic activity. The scavenging rate on ABTS, DPPH, hydroxyl and superoxide radicals was all beyond 60% as SBP-1 concentration reached 4 mg/mL, and the inhibition rate on α-glucosidase and α-amylase was both more than 80%, which was closely to that of acarbose.