AA generates H₂O₂ in a cell-free system that is dependent on the presence of free transition metal ions. (A) Different concentrations of AA (○) and DHA (•) were incubated in IMDM for 1 hour at 37°C and H₂O₂ was determined by Amplex red. (B) The generation of H₂O₂ by 1 mM AA in IMDM in the presence or absence of 500 U/mL catalase. (C) Generation of H₂O₂ by 100 μM of AA or 10 μM CuCl₂ in IMDM and increasing concentrations of DMP. (D) Generation of H₂O₂ by 50 μM of AA and increasing concentrations of As₂O₃ or 10 μM CuCl₂ in 50 mM sodium phosphate buffer (pH 7.4). (A-D) Experiments were performed in triplicate and are expressed as the mean ± SD of 2 independent experiments.