There are two types of antioxidant systems in the body, one is the enzymatic antioxidant system, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px). The other is a non-enzymatic antioxidant system, including uric acid, vitamin C, vitamin E, glutathione, bilirubin, α-lipoic acid and carotenoids. Antioxidant capacity is thought to be the cumulative effect of all antioxidants in blood and body fluids

Fe3+-TPTZ can be reduced by antioxidants and produce blue Fe2+-TPTZ under acid condition. The antioxidant capacity of sample can be calculated by detection the absorbance value at 593 nm.

1. Preparation of standard

Dilute 100 mmol/L FeSO4 solution with distilled water (See Note b) to a serial concentration. The recommended dilution gradient is as follows: 0, 0.3, 0.6, 0.9, 1.2, 1.8, 2.1, 2.5 mmol/L.

2. Operation table

Note: a. A standard curve is required for every batch of experiments.

b. For serum, plasma, saliva, urine and other liquid samples, it is recommended to use distilled water or 1×PBS to prepare the standard solution. For cell or tissue samples, it is recommended to use homogenate medium to prepare the standard solution.