Open Access

Simone Fulda, Thomas Efferth

• Secondary plant metabolites reveal numerous biological activities making them attractive as resource for drug development of human diseases. As the majority of cancer drugs clinically established during the past half century is derived from nature, cancer researchers worldwide try to identify novel natural products as lead compounds for cancer therapy. Natural products are considered as promising cancer therapeutics, either as single agents or in combination protocols, to enhance the antitumor activity of additional therapeutic modalities. Most natural compounds exert pleotrophic effects and modulate various signal transduction pathways. A better understanding of the complex mechanisms of action of natural products is expected to open new perspectives in coming years for their use alone or in combination therapies in oncology. Two major strategies to identify novel drug candidates from nature are the bioactivity-guided fractionation of medicinal plant extracts to isolate cytotoxic chemicals and the identification of small molecules inhibiting specific targets in cancer cells. In the present review, we report on our own efforts to unravel the molecular modes of action of phytochemicals in cancer cells and focus on resveratrol, betulinic acid, artesunate, dicentrine and camptothecin derivatives.