Monoamine Oxidase B inhibitor 5 (Compound 16d) is a selective and reversible inhibitor for monoamine oxidase B ( hMAO-B ) with an IC 50 of 67.3 nM and a K i of 82.5 nM. Monoamine Oxidase B inhibitor 5 exhibits good pharmacokinetic characters and weak toxicity in rats model. Monoamine Oxidase B inhibitor 5 alleviates MPTP-induced motor impairment in Parkinson’s mouse model. Monoamine Oxidase B inhibitor 5 is blood-brain barrier (BBB) penetrate.