Novel polysaccharide from Chaenomeles speciosa seeds: Structural characterization, α-amylase and α-glucosidase inhibitory activity evaluation

Purification and structural characterization of a novel polysaccharide fraction from Chaenomeles speciosa seeds were investigated. After hot water extraction and ethanol precipitation, the crude polysaccharide was sequentially purified with Cellulose DEAE-52 and gel-filtration chromatography, and a highly purified polysaccharide fraction (F3) was obtained. The structure of F3 was characterized by high-performance gel permeation chromatography (HPGPC), high performance liquid chromatography (HPLC), ultraviolet-visible (UV), Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectrum, together with methylation, scanning electron microscopy (SEM), atomic force microscope (AFM), and Congo-red test analysis. The results indicated that F3 was a homogeneous polysaccharide fraction with a molecular weight of 8.65 x 10(6) Da, and it was composed of Rha, GlcA, Gal, and Ara in a molar ratio of 6.34:5.73:47.14:40.13. The backbone of F3 was consisted of -> 3,6)-Galp-(1 ->, and the side chains of F3 were composed of Araf-(1 ->, -> 4)-GlcpA-(1 ->, -> 4)-Galp-(1 -> and -> 3)-Rhap-(1 ->. The hypoglycemic assays demonstrated F3 had good alpha-amylase and alpha-glucosidase inhibition activities, and their IC50 values were 6.24 mg/mL and 4.59 mg/mL respectively. Thus, the polysaccharide from Chaenomeles speciose could be applied as a potential natural source in retarding postprandial hyperglycemia effects. (C) 2020 Elsevier B.V. All rights reserved.