Characterization and inhibitory activities on α-amylase and α-glucosidase of the polysaccharide from blue honeysuckle berries

An acidic heteropolysaccharide HEP-2 was obtained from blue honeysuckle berry extracts after purification using Sepharose 6B and Sephadex G-200 column chromatography. The molecular weight of HEP-2, determined with high-performance gel permeation chromatography, was 3.01 × 106 Da. Fourier transform infrared spectroscopy, gas chromatography and nuclear magnetic resonance analyses revealed the presence of α-, β-pyranose ring and six sugar residues in HEP-2. Amorphous aggregates of HEP-2 with irregular shape and lacking the triple helical structure were detected using the Congo red test, scanning electron and atomic force microscopy, and X-ray diffraction studies. Rheological characterization showed typical shear-thinning behavior and viscoelastic property of the polysaccharide. HEP-2 exerted significant inhibitory effects on α-amylase and α-glucosidase and displayed competitive inhibition kinetics. The collective results support the potential utility of HEP-2 as a hypoglycemic agent for enzyme-targeted treatment of diabetes or functional food.