New halogenated 3-phenylcoumarins as potent and selective MAO-B inhibitors

With the aim to find out the structural features for the MAO inhibitory activity and selectivity, in the present communication we report the synthesis and pharmacological evaluation of a new series of bromo-6-methyl-3-phenylcoumarin derivatives (with bromo atom in both different benzene rings of the skeleton) with and without different number of methoxy substituent at the 3-phenyl ring. The methoxy substituents were introduced, in this new scaffold, in the meta and/or para positions of the 3-phenyl ring. The synthesized compounds 3-7 were evaluated as MAO-A and B inhibitors using R-(-)-deprenyl (selegiline) and iproniazide as reference inhibitors, showing, most of them, MAO-B inhibitory activities in the low nanomolar range. Compounds 4 (IC(50)=11.05 nM), 5 (IC(50)=3.23 nM) and 6 (IC(50)=7.12 nM) show higher activity than selegiline (IC(50)=19.60 nM) and higher MAO-B selectivity, with more than 9050-fold, 30,960-fold and 14,045-fold inhibition levels, with respect to the MAO-A isoform.