Twenty-nine arylisopropylamines, substituted at the β-position of their side chain by an oxo, hydroxy, or methoxy group, were evaluated in vitro as MAO-A and MAO-B inhibitors. The oxo derivatives (cathinones') were in general less active as MAO-A inhibitors than the corresponding arylisopropylamines, but exhibited an interesting MAO-B inhibiting activity, which was absent in the hydroxy, methoxy, and β-unsubstituted analogues. These results ...