A number of unsubstituted aromatic hydrocarbons, azaheterocycles, oxaheterocycles and cyclic ketones were screened for their inhibitory potency towards monoamine oxidases (MAO; EC 1.4.3.4.) A and B. Fair activities (IC50 10-100 microM) and selectivities were found for, e.g. naphthalene, anthracene, phenanthrene, isoquinoline and acridine. The most active inhibitors are oxygen-containing compounds (e.g. coumarin, flavone, dibenzofuran, xanthene, thioxanthone and acridone), with xanthone emerging as a potent (IC50 0.8 microM) and reversible MAO-A inhibitor. All tested inhibitors seem to act in a reversible and time-independent manner.
