The Cu2+-chelating properties of aqueous garlic extracts were assessed using an approach based upon restoring the activity of xanthine oxidase which has been inhibited in the presence of 0.050 mM CuSO4. The activity of xanthine oxidase can be assessed by monitoring either the production of superoxide anion (measuring the reduction of NBT at 560 nm) or the formation of uric acid (following absorbance at 295 nm). Xanthine oxidase activity would be restored if the garlic extracts were able to chelate Cu2+. Panel A shows xanthine oxidase activity measuring uric acid production at 295 nm. ap < 0.0001 vs. CT (-Cu2+), bp < 0.0001 vs. CT (+Cu2+), cp < 0.0001 vs. its respective group without Cu2+. Panel B shows xanthine oxidase activity measuring superoxide production by NBT reduction at 560 nm. ap < 0.0001 vs. CT (-Cu2+); bp < 0.0001 and cp < 0.05 vs. CT (+Cu2+); dp < 0.05 vs. its respective group without Cu2+. CT = Control (-Cu2+, +Cu2+), GP = aqueous extracts of garlic powder, HGP = heated aqueous extracts of garlic powder, RG = aqueous extracts of raw garlic, HRG = heated aqueous extracts of raw garlic, BG = aqueous extracts of boiled garlic, MG = aqueous extracts of microwave-treated garlic, and PG = aqueous extracts of pickled garlic. GP and HGP = 0.1 mg/mL, RG, HRG, BG, MG, and PG = 0.5 mg/mL. Data are mean ± SEM of 3 determinations, except for both CT groups and EDTA group in which n = 7.