2.2.3. Metal Ion Chelation Activity Assay

Fe2+ chelation activities were determined according to the methods described by Zhang [15] with some modifications. First, 0.05 mL of 2 mM FeCl2 was mixed with 0.1 mL of 5 mM ferrozine. After the addition of samples solutions, the final volume was increased up to 3 mL with ultrapure water. The absorbance change was measured at 562 nm after being incubated for 10 min at room temperature. The metal ion chelation activity was calculated by Equation (3).

$$\text{Metal ion calculation activity} \%= (1 - A\_{\text{sample}}/A\_{\text{blank}}) \times 100\tag{3}$$

where A means absorbance value of samples (Asample) and blank (Ablank) at 562 nm.
