The role of weeds as sources of pharmaceuticals.

Primary tropical forest is generally considered to be the most likely habitat to discover new pharmaceuticals, due to high biodiversity and endemism. However, many indigenous groups rely on non-forested disturbed environments for medicinal plants. An ethnobotanical approach to drug discovery suggests that these disturbed environments may also harbor potentially useful medicinal compounds. Despite the neglect by current researchers to conduct drug discovery in disturbed environments, many source plants for modern pharmaceuticals thrive in disturbed areas. An analysis of the 101 plant species from which 119 contemporary pharmaceuticals are derived shows that at least 36 of these plants are considered weeds (Chi 2 = 343.34, P<0.0001). These results are an order of magnitude higher than what would be predicted by random occurrence of weeds in the modern pharmacopeia. Biochemical evidence based on literature is presented to explain this occurrence. This finding suggests that disturbed habitats may be important areas to search for novel compounds in drug discovery.