50 µL of sample extracts were added to 1.5 mL of the FRAP reagent and mixed well. The absorbance was measured at 593 nm using a microplate reader spectrophotometer (EPOCH Microplate Spectrophotometer, Vermont, USA) after 4 min. The standard curve of iron (II) sulfate solutions (200, 400, 600, 800 and 1000 mg L−1) was prepared using the similar procedure and all samples were measured in three replicates. Results were expressed as µmol Fe (II)/100 g dry weight.