Abstract: In order to explore the antioxidant functional group in phycocyanin, the antioxidant activities of five different phycocyanins were determined by ferric ion reducing antioxidant power (FRAP), 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging, pyrogallol autooxidation and oxygen radical absorbance capacity (ORAC) assays, and their relationship with protein content, chromophore content and phycocyanin purity was analyzed. The results showed that in the FRAP and ABTS radical cation systems, the antioxidant activity of phycocyanins, dominated by electron transfer, was positively correlated with protein content, indicating that the protein components are mainly responsible for the antioxidant effect of phycocyanins. In the pyrogallol autooxidation system, the antioxidant activity of phycocyanins was positively correlated with protein content but negatively correlated with chromophore content, indicating that the antioxidant activity of phycocyanins is attributed to the protein components. In the ORAC system, the antioxidant activity of phycocyanins was positively correlated with chromophore content and phycocyanin purity, indicating that the chromophore plays a principal role in the antioxidant effect of phycocyanins.

Key words: phycocyanin; purity; chromophore; antioxidant effect