Degradation of blue honeysuckle polysaccharides, structural characteristics and antiglycation and hypoglycemic activities of degraded products

In this study, H2O2-Vc (hydrogen peroxide-ascorbic acid) oxidation system under 50 and 70 °C was developed to degrade blue honeysuckle polysaccharides. The results suggested that viscosity-average molecular weight was decreased and reducing sugar content was raised with the rise of time or temperature. The degradation was fitted to the second-order reaction kinetics. The gas chromatography revealed two degraded polysaccharides were consisted of six monosaccharides (Gal A, Rha, Ala, Gal, Glu, Man) with different ratios, and eight types of sugar residues were confirmed using nuclear magnetic resonance. Based on the linearity (R1), branching (R2), branch size (R3) calculation, PD70 (purified degraded polysaccharide at 70 °C) had a more linear structure and longer side chains comparing to PD50 (purified degraded polysaccharide at 50 °C). The absence of triple helical structure and sheet-like aggregation with rough surface were confirmed by the Congo red test and scanning electron. Rheological characterization proved the two degraded polysaccharides exhibited shear-thinning behavior and viscoelastic property. Besides, the two degraded polysaccharides displayed strong antiglycation activities, inhibitory effects against α-amylase and α-glucosidase, and exhibited competitive inhibitory kinetics. These findings support the potential application of blue honeysuckle polysaccharides as the treatment of diabetes.