Antioxidative and Chelating Properties of Anthocyanins in Azolla imbricata Induced by Cadmium

To investigate the biological activities of anthocyanins, which are induced by cadmium in A. imbricata, the antioxidant properties of anthocyanins were investigated using various antioxidant assays, namely 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, 2,2'-azinobis-(3-ethylbenzthiazoline-6sulfonic acid) (ABTS) radical scavenging activity, reducing power, and β-carotene bleaching assay. Results showed that anthocyanins exhibited excellent antioxidant activities in all assays and the EC50 values of DPPH radicals scavenging, ABTS radicals scavenging, reducing power and β-carotene bleaching assay were 19.08, 10.69, 40.93, and 44.19 μg·mL, respectively. The Cd chelation potency of anthocyanins was also investigated in vitro. Under given conditions, Cd chelating ability of anthocyanins increased significantly with increase in contact time, anthocyanins concentration in dialysis tubing and Cd concentration in solution. Based on these results, anthocyanins inducibly synthesized by Cd treatment was a powerful antioxidant, as well as Cd chelator, might play a role in detoxification of Cd in A. imbricata.