Ultrasound-assisted modified pectin from unripe fruit pomace of raspberry (Rubus chingii Hu): Structural characterization and antioxidant activities

With the aim of making full use of the resource of Rubus Chingii Hu, this work comparatively investigated the structural characterization and antioxidant activities of pectin (RP) from unripe fruit pomaces of Rubus chingii Hu and ultrasonic-modified pectin (URP) from unripe fruit pomaces of Rubus Chingii Hu. Compared with the original RP, ultrasound treated RP (URP) significantly changed the chemical composition. The scanning electron microscopy (SEM) results suggested that the conformation of RP was filiform, smooth and slim and a large number of spherical pectins were produced by ultrasonic modification. Both RP and URP exhibited the potential antioxidant activity and α-glucosidase inhibitory activity. Moreover, RP and URP effectively attenuated the oxidative damage induced by H2O2 and reduced intracellular reactive oxygen species (ROS) levels in human hepatic L02 cells and URP showed higher activity than RP. These results suggested that the unripe fruit pomace of Rubus chingii Hu could be used as a potential resource to obtain the antioxidant pectin and the ultrasound-assisted modification could significantly change the physical structure of pectin and effectively improve its antioxidant activities.