TABLE 9–2 New Chemical Structures of Natural Origin Reported in 1985a

Source

Pharmacological Evaluation

Tested

Not Tested

Higher Plants

Gymnosperms

2

48

Dicots

238

2,144

Monocots

10

112

Pteridophytes

0

40

Bryophytes

0

24

 

250 (9.5%)

2,368

Lower Plants

Lichen

0

0

Fungi

74

106

Schizomycetes

216

114

 

290 (56.6%)

220

Other

Marine organisms

82

280

Protozoa

4

0

Arthropods

4

0

Chordates

0

2

 

90 (23.9%)

282

aFrom NAPRALERT data base at the University of Illinois at Chicago.

Approaches to Drug Discovery from Plants

There are many approaches to the search for new biologically active principles in higher plants (Farnsworth and Loub, 1983). One can simply look for new chemical constituents and hope to find a biologist who is willing to test each substance with whatever pharmacological test is available. This is not considered to be a very valid approach. A second approach is simply to collect every readily available plant, prepare extracts, and test each extract for one or more types of pharmacological activity. This random collection, broad screening method is a reasonable approach that eventually should produce useful drugs, but it is contingent on the availability of adequate funding and appropriate predictable bioassay systems. The last major useful drugs to have reached the marketplace based on this approach are the so-called vinca alkaloids, vincristine sulfate (leurocristine) and vinblastine sulfate (vincaleukoblastine). Vincristine is the drug of choice for the treatment of childhood leukemia; vinblastine is a secondary drug for the treatment of Hodgkin’s disease and other neoplasms.

Vincristine was discovered by Gordon H.Svoboda at the Lilly Research Laboratories. In January 1958, Svoboda submitted an extract of the Madagascan periwinkle plant [Catharanthus roseus (L.) G. Don] to a pharmacological screening program at Lilly (Farnsworth, 1982). This was the fortieth plant that he selected for inclusion in the program. Vincristine was marketed in the United States in 1963, less than 5 years after a crude extract of C. roseus was observed to have antitumor activity. In 1985, total domestic and international sales of vincristine



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement