Renealmia alpinia (Zingiberaceae), a medicinal plant of tropical rainforests, is used to treat snakebites, as a febrifuge, analgesic, antiemetic, antiulcer, and anticonvulsant. The dichloromethane extract of R. alpinia leaves showed potent inhibition of recombinant human MAO-A and -B. Phytochemical studies yielded six known compounds including, pinostrobin, pinostrobin chalcone, sakuretin, sakuretin-4'-methyl, yashabushidiol, and desmethoxyyangonin. Desmethoxyyangonin displayed strong inhibition of MAO-A and -B (Ki values 0.922 and 0.031µM, respectively), with about 30 fold more selectivity against MAO-B. The kinetic analysis of the inhibition and equilibrium dialysis dissociation assay of the enzyme-inhibitor complex showed reversible binding of desmethoxyyangonin with MAO-A and -B. Selective reversible inhibitors of MAO-B have important therapeutic value for treatment of neurodegenerative disorders and Parkinson's Disease.