We investigated the antioxidant properties of two synthetic diarylamines, MJQ1 and MJQ2. For one of them (MJQ1) the synthesis procedure is herein described. The compounds showed maximal protection of ADP/Fe(2+) induced mitochondrial lipid peroxidation for 50nM (MJQ1) and 60muM (MJQ2) concentrations. Both compounds were also effective in the prevention of mitochondrial DeltaPsi collapse. The effective antioxidant dose of MJQ1 in mitochondria (50nM) also proved to protect lipid peroxidation in PC12 cells and the effect seems not to be related with the compound's iron chelating ability. The modified structure of MJQ1 clearly resulted in an improvement of its antioxidant and toxic profile, evaluated in mitochondria and whole cells. This study demonstrates a high potential of these diarylamines, as radical scavengers, whose chemical structures can be manipulated if a specific target is well characterized.