Ultrasonic degradation ofPolysaccharides from Auricularia auricula and the antioxidant activity of their degradation products

Auricularia auricula polysaccharide (AAP) were purified and degraded using ultrasonic wave with the degradation kinetics model fitted to 1/M-t - 1/M-0 = k . t. Followed that the morphology, intrinsic viscosity, viscosity-average molecular weight, antioxidant activity of AAP and their degradation products were in vitro investigated. Results showed the intrinsic viscosity and viscosity-average molecular weight of AAP decreased significantly (p < 0.05) with increasing ultrasonic time and their microscopic sizes were reduced after degradation. In addition, ultrasonic wave destroyed the helix structure and changed the monosaccharide proportion of AAP. SEM analysis displayed some morphological difference existing in polysaccharides before and after degradation. More importantly, the antioxidant activities in vitro of AAP after degradation were significantly increased (p < 0.05) and AAP(UD12h), displayed the strongest antioxidant activity. These results indicate that ultrasonic degradation may be a suitable way to improve the antioxidant activity of natural polysaccharides.