A series of (2E, 4E)-1-(2-hydroxyphenyl)-5-phenylpenta-2, 4-dien-1-ones (3a–r) and (2Z, 4E)-3-hydroxy-1-(2-hydroxyphenyl)-5-phenylpenta-2, 4-dien-1-ones (6a–l) were synthesized and evaluated in vitro as inhibitors of the two human Monoamine oxidase (hMAO) isoforms, MAO-A and MAO-B. Most of the compounds showed a selective MAO-B inhibitory activity in the nanomolar or low micromolar range.(2E, 4E)-5-(4-Chlorophenyl)-1 ...