Monoamine oxidase B (MAO-B) inhibitors were isolated from the bark of a Brazilian plant, Himatanthus sucuuba (SPR.). Assignments of the ¹H-and ¹³C-NMR data using two dimensional (2D)-NMR techniques showed the active components to be known lichen depsides, confluentic acid (1) and 2'-O-methylperlatolic acid (2). The depside (1) showed selective inhibition of MAO-B with IC₅₀ value of 0.22μM.