Enzymatic Hydrolysis of Polysaccharide from Houttuynia cordata and Structure Characterization of the Degradation Products and Their α-Glucosidase Inhibitory Activity

This study aimed to enhance the α-glucosidase inhibitory activity of Houttuynia cordata polysaccharide (HCP) and investigate the structure of derivatives. Under optimal conditions (amylase derived from Aspergillus oryzae loading of 15 U/mL, 60 °C, and pH 6.1), the enzymatic hydrolysates of HCP (EHCP) demonstrated significantly higher α-glucosidase inhibition than non-enzymatically treated HCP (NEHCP). At a 6 mg/mL concentration, the α-glucosidase inhibition rates of EHCP and NEHCP were 77.32% and 52.92%, respectively. Molecular weight analysis revealed that EHCP was a homogeneous polysaccharide of 338.7 kDa, lower than that of NEHCP (504.6 kDa). The monosaccharide composition was Galacturonic acid/Glucuronic acid/Galactose/Rhamnose/Mannose/Fucose/Xylose/Arabinose/Glucose = 77.42:3.78:8.04:2.12:3.16:2.48:0.75:0.17:2.08 molar ratio. Infrared and nuclear magnetic resonance analyses confirmed pyranose rings and both α- and β-glycosidic linkages. Compared with NEHCP, EHCP demonstrated improved solubility, decreased crystallinity, and morphological changes from dense rod-like to loose flaky structures.