Preparation, characterization, and α-glycosidase inhibition activity of a carboxymethylated polysaccharide from the residue of Sarcandra glabra (Thunb.) Nakai

A carboxymethylated polysaccharide (CMSERP) was prepared from the residue of Sarcandra glabra (Thunb.) Nakai. CMSERP was mainly composed of galacturonic acid (GalA), glucose (Glc), galactose (Gal), glucuronic acid (GlcA), arabinose (Ara), rhamnose (Rha), xylose (Xyl), ribose (Rib), and fucose (Fuc) at the ratio of 29.79:19.30:11.92:6.32:4.68:3.95:3.39:2.31:1.00. The primary structure features of CMSERP were determined to be a pectin like polysaccharide according to FT-IR, NMR, and HPAEC-PAD. The results of HPSEC-MALLS-RID and DLS indicated the Mw, Mn, Mz, and S 2 Z 1/2 $\mathrm{S}^{\mathrm{2}}{}_{\mathrm{Z}}{}^{\mathrm{1/2}}$ of CMSERP were 5.515   ×   10 4   g/mol, 1.566   ×   10 4   g/mol, 1.510   ×   10 6   g/mol, and 62.8 (±1.2%) nm, respectively. TEM and AFM revealed CMSERP was dispersed in 0.05   M sodium sulfate but aggregated in water. Moreover, a high α-glucosidase inhibition activity (83.38%   ±   2.30% at 1000   μg/mL) of CMSERP which is higher than that of acarbose was observed. The results proved the effects of carboxymethylation on poor water-soluble polysaccharides and explore a potential α-glucosidase inhibitor which from abandoned extracted residue for the functional foods and pharmaceutical industries.