Determination of antioxidant
The activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) were measured using enzymatic activity assay kits (Comin Biotechnology, Suzhou, China). The whole procedure was conducted following the instructions of the manufacturer. The SOD, POD, CAT, and APX activities were measured with an EPOCH ultraviolet spectrophotometer (BioTek, Vermont, U.S.A) at OD560, OD470, OD240 and OD290, respectively.