Quinolone alkaloids from evodiae fructus and their inhibitory effects on monoamine oxidase.

1-Methyl-2-undecyl-4(1H)-quinolone (1) was previously isolated as a selective MAO-B inhibitor from the Evodiae Fructus. Further bioassay-guided purification led to the identification of five known quinolone alkaloids, 1-methyl-2-nonyl-4(1H)-quinolone (2), 1-methyl-2-[(Z)-6-undecenyl]-4(1H)-quinolone (3), evocarpine (4), 1-methyl-2-[(6Z,9Z)-6,9-pentadecadienyl]-4(1H)-quinolone (5), and dihydroevocarpine (6). All the isolates showed more potent inhibitory effects against MAO-B compared to MAO-A. The most MAO-B selective compound 5 among the isolates inhibited MAO-B in a competitive manner, according to kinetic analyses by Lineweaver-Burk reciprocal plots.