Abstract In the present study, a series of 3, 4-dihydro-2 (1H)-quinolinone derivatives were synthesized and evaluated as inhibitors of recombinant human monoamine oxidase (MAO) A and B. The 3, 4-dihydro-2 (1H)-quinolinone derivatives are structurally related to a series of coumarin (1-benzopyran-2-one) derivatives which have been reported to act as MAO-B inhibitors. The results document that the quinolinones are highly potent and selective ...