Preliminary structural characterization and hypoglycemic effects of an acidic polysaccharide SERP1 from the residue of Sarcandra glabra

An acidic polysaccharide (SERP1) was isolated from the residue of Sarcandra glabra (Thunb.) Nakai by water extraction and purified by decoloration and ion exchange chromatography. The structure of SERP1 was determined by HPLC, HPSEC-MALLS, FT-IR, and NMR. The results indicated that SERP1 was a homogeneous heteropolysaccharide with the absolute molecular weight of 4.208 × 104 Da in the aqueous phase. 1,4-linked α-d-galacturonic acid, methyl esterified 1,4-linked α-d-galacturonic acid, 1,4-linked α-d-glucuronic acid, 1,5-linked α-l-arabinose, 1,3-linked β-d-galactose 1,4-linked α-d-glucose, 1,4,6-linked β-d-glucose, 1,6-linked β-d-glucose, and 1,2-linked rhamnose existed in SERP1. In vitro α-glucosidase inhibition assay indicated that SERP1 had a low IC50 value of 49.01 μg/mL, which exhibited stronger α-glucosidase enzyme inhibitory activity than acarbose at the same concentration. The treatment of SERP1 to type 2 diabetes mellitus mice alleviated the hyperglycemia, increased glucose utilization of peripheral tissues of the liver and inhibited the liver injury. This study provides a possible exploration to use valuable industrial waste.