Chemical modification and influence of function groups on the in vitro-antioxidant activities of porphyran from Porphyra haitanensis

Porphyran extracted from Porphyra haitanensis is a sulfated polysaccharide, which possesses excellent antioxidant activities. In this study, we prepared porphyran and alkali-treated porphyran and their derivatives, sulfated porphyran and acetylated porphyran. Their antioxidant activities including scavenging effect on superoxide radical, 1,1-diphenyl-2-picrylhydrazyl radical and reducing power were investigated. The results of chemical analysis and FT-IR spectrums indicated that the modification was successful. And in addition, we found that certain derivative exhibited stronger antioxidant activity than raw material porphyran. The sulfated derivative with certain DS showed stronger antioxidant activity. The acetylated derivative showed the most excellent antioxidant activity in three assays we made, and so this derivative needs to be attended to.