Effect of Ultrasonic Degradation on In Vitro Antioxidant Activity of Polysaccharides from Porphyra yezoensis (Rhodophyta)

This article aims to study the effect of ultrasonic degradation on antioxidant activity of polysaccharides from Porphyra yezoensis (Rhodophyta) (PSPY), and to look for the relationship between molecular structure of fractions (F1, F2, and F3) from ultrasonic-degraded PSPY (UDPSPY) and their activities of scavenging hydroxyl and superoxide anion radicals, chelating ability of iron ion and reducing power. Results of antioxidant assays indicated that the UDPSPY had higher antioxidant activity of scavenging superoxide anion radical and hydroxyl radical than that of the PSPY. As antioxidant activities of the fractions are concerned, this result might suggest that decreasing molecular weight and increasing sulfate group content in the molecule were vital and necessary factors for improving antioxidant activity of PSPY. Decrease of molecular weight was the dominant reason for increasing activities of scavenging non-site and site specific hydroxyl radical and reducing power of F1, F2, and F3, and increase of sulfate group content in the molecule was the dominant reason for increasing activities of scavenging superoxide anion radical and chelating ferrous ions of F1, F2, and F3. It was possible that ultrasonic treatment could be a new and effective method for enhancing PSPY's antioxidant activity.