Effect of ultrasonic degradation on the physicochemical property, structure characterization, and bioactivity of Houttuynia cordata polysaccharide

This study aimed to evaluate the influence of ultrasonic degradation on Houttuynia cordata polysaccharide (HCP) physicochemical properties, structure characterization, and bioactivities. The results indicated that the ultrasonic degradation could significantly decrease HCP's molecular weight (MW). Total polysaccharide, uronic acid content, solubility, and thermal stability of HCP increased gradually with the increase in ultrasonication power. Fourier transform infrared (FTIR) and Nuclear magnetic resonance spectroscopy (NMR) spectra proved that the primary structure of HCP had not been changed via ultrasonic degradation. Antioxidant and hypoglycemic activity results confirmed that ultrasonication enhanced the ability to scavenge free radicals (DPPH, ABTS, and OH) and improved α-glycosidase and α-amylase inhibition with the increase of ultrasonic power, which was increased in order HCP <U200 < U400 < U600. The degraded HCP produced via 600 W presented the best physicochemical properties and bioactivities. U600, α-amylase and α-glycosidase inhibition activities were 43.80 ± 0.68 and 83.28 ± 2.56 %, which were higher than those of native HCP 38.40 ± 0.53 and 65.67 ± 0.54 %, respectively, at a concentration of 10 mg/mL HCP solution. These results suggested that ultrasonication could be used as a green method for polysaccharide degradation and showed potential application for enhancing polysaccharide bioactivities for functional foods and pharmaceutical applications.