CHAPTER 9
SCREENING PLANTS FOR NEW MEDICINES

NORMAN R.FARNSWORTH

Research Professor of Pharmacognosy, Program for Collaborative Research in the Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, Illinois

The U.S. pharmaceutical industry spent a record $4.1 billion on research and development in 1985, an increase of 11.6% from 1984 (Anonymous, 1986). In the same year, the American consumer purchased in excess of $8 billion in community pharmacies for prescriptions whose active constituents are still extracted from higher plants (Farnsworth and Soejarto, 1985). For the past 25 years, 25% of all prescriptions dispensed from community pharmacies in the United States contained active principles that are still extracted from higher plants, and this percentage has not varied more than 1.0% during that period (Farnsworth and Morris, 1976). Despite these data, not a single pharmaceutical firm in the United States currently has an active research program designed to discover new drugs from higher plants.

THE GLOBAL IMPORTANCE OF PLANT-DERIVED DRUGS

Approximately 119 pure chemical substances extracted from higher plants are used in medicine throughout the world (Farnsworth et al., 1985) (see Table 9–1). At least 46 of these drugs have never been used in the United States. For the most part, the discovery of the drugs stems from knowledge that their extracts are used to treat one or more diseases in humans. The more interesting of the extracts are then subjected to pharmacological and chemical tests to determine the nature of the active components. Therefore, it should be of interest to ascertain just how important plant drugs are throughout the world when used in the form of crude extracts. The World Health Organization estimates that 80% of the people in



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