2.5. Determination of chelating activity The chelating activity of samples on Fe was measured as pre- viously described (Carter, 1971). The samples (0.2-1 mg/ml. 0.5 ml) thus prepared were reacted with Feci2 (2 mM, 0.25 ml) and ferrozine (5 mM, 0.25 ml) for 10 min, and the absorbance at 562 nm was determined. A lower level of absorbance indicated a higher chelating activity of samples.