Ferrous ions play an important role as catalysts in oxidative process, leading to the formation of hydroxyl radicals and hydroperoxide decomposition by Fenton reaction. The chelating ability assayed is the ability of extracts to inhibit the complex formation of
ferrozine with ferrous ions. Aqueous extracts were 16.8-22.9-fold more effective in chelating abilities on ferrous ions than ethanolic extracts for both ginger rhizomes as evidence by their lower EC50 values (Table 4). In addition, EC50 values of CG were lower than those of GG for both extracts. However, EDTA was much more effective with its EC50 value being 0.14 mg/mL.