constituent species contain potentially useful drugs. This is a sad commentary when one considers that interest in plants as a source of drugs started at the beginning of the nineteenth century and that technology and science have grown dramatically since that time.
As shown in Table 9–1, the 119 plant-derived drugs in use throughout the world today are obtained from less than 90 species of plants (Farnsworth et al., 1985). How many more can be reasonably predicted to occur in the more than 250,000 species of plants on Earth?
It is possible to present certain types of data showing the relative interest in studying natural products as a source of drugs by means of the NAPRALERT data base that we maintain at the University of Illinois at Chicago (Farnsworth et al., 1981, 1983; Loub et al., 1985). This specialized computer data base of information on natural products was derived from a systematic search of the world literature. Data that can be retrieved from the system include folkloric medicinal claims for plants, the chemical constituents contained in plants (and other living organisms), the pharmacological effects of naturally occurring substances, or the pharmacological effects of crude extracts prepared from plants. More than 80,000 articles have been entered into the data base since 1975, and about 6,000 new articles are added each year. The system contains folkloric, chemical, or pharmacological information on about 25,000 species of higher plants alone.
To give some idea as to the interest (or lack thereof) in studying the pharmacological effects of natural products, we can cite the following data from NAPRALERT. In 1985, approximately 3,500 new chemical structures from natural sources were reported. Of these, 2,618 were obtained from higher plants, 512 from lower plants (lichens, filamentous fungi, and bacteria), and 372 from other sources (marine organisms, protozoa, arthropods, and chordates) (Table 9–2). A significant 56.6% of the new chemicals obtained from lower plants (primarily antibiotics produced in industrial laboratories) were reported to have been tested for biological effects. About 23.9% of those obtained from marine sources, protozoa, arthropods, and chordates were studied for biological effects, but only 9.5% of the new structures obtained from higher plants were tested for pharmacological effects. The probable reasons for the low, 9.5% figure are that a majority of these discoveries were reported from university laboratories where the interest is mainly on chemistry, where there is less interdisciplinary research (i.e., botanists, chemists, and biologists working in collaboration), and where routine testing services for pharmacological activity are not readily available.
Why is there so little interest and activity in plant-derived drug development in the United States? An attempt will be made to answer this question, but first it is important to describe briefly some of the more fruitful approaches to drug discovery from higher plants.