Multidrug resistance (MDR) is a preocupying phenomenon which originates cells with high resistance to several chemotherapeutic drugs, with distinct structures and functions. It may occcur due to the overexpression of transporters belonging to the ABC superfamily. Pdr5p, from Saccharomyces cerevisiae, belongs to this family. One of the strategies used in the fight to overcome this problem is the search for new substances, which could act as inhibitors for these transporters. The phytochemical study of different plant species may take to the discovery of new drugs from natural origin. In this work, we have studied the inhibitory effects of the crude extract (as well as its fractions) of Cabralea canjerana, a plant species found in the Atlantic forest, on Pdr5p catalytic activity. The IC₅₀ result obtainded was of approximately 5 mg/ml for the crude ethanolic extract. This extract was partitioned against solvents of growing polarities (hexane, dichloromethane, ehtyl acetate and butanol) and the new partitions were tested against Pdr5p ATPase activity in a fixed concentration of 10 mg/ml. We observed that some partitions were able to exhibit a similar ihibition profile than the original ethanolic extract. The best result was obtained with the dichloromethane partition, which was submitted to counter-current chromatography, in order to isolate the active compounds, which are being identified through spectroscopic methods.