Bioassay-guided fractionation monitored by mushroom tyrosinase (EC 1.1
4.18.1) activity, afforded six inhibitors from three Bolivian medicina
l plants, Buddleia coriacea, Gnaphalium cheiranthifolium, and Scheelea
princeps. These inhibitors, which are all known phenolic compounds, i
nhibited the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) mediat
ed by a mushroom tyrosinase.