The fate of xenobiotics in the organism and their toxic or therapeutic influence have been under intensive investigation in recent years. The compounds are searched for which affect as preventive agents cancerogenesis and other disorders caused by procancerogens and pro-mutagens from the environment. The main focus is on the compounds able to modulate the activity of enzymes of the Ist and IInd phase of xenobiotic detoxication or compounds with antioxidative activity. In the following review,comopunds of natural origin are presented which possess an ability tomodulate the processes connected with detoxication of xenobiotics. These compounds. could be usable as preventive agents against some diseases or as supportive pharmaceuticals during chemotherapy.

        Key words: chemoprotective activity – cytochrome P450 – natural compounds