MAO-B-IN-9 is a monoamine oxidase B MAO-B inhibitor (IC50: 0.18 µM) that crosses the blood-brain barrier with potency, selectivity and time-dependence. MAO-B-IN-9 has neuroprotective effects against Abeta1-42-induced neuronal cell death, which may be related to the anti-aggregation effect of Abeta1-42.