Discovery of new medicines from plants
(Nutraceutical use versus drug development)
Little work was carried out by the pharmaceutical industry during 1950–1980s; however, during the 1980–1990s, massive growth has occurred.
This has resulted in new developments in the area of combinatorial chemistry, new advances in the analysis and assaying of plant materials and a heightened awareness of the potential plant materials as drug leads by conservationists.
New plant drug development programmes are traditionally undertaken by either random screening or an ethnobotanical approach, a method based on the historical medicinal/food use of the plant.
Tropical forests have produced only 47 major pharmaceutical drugs of world-wide importance.
It is estimated that a lot more, say about 300 potential drugs of major importance may need to be discovered.
These new drugs would be worth $147 billion.
It is thought that 125,000 flowering plant species are of pharmacological relevance in the tropical forests.
It takes 50,000 to 100,000 screening tests to discover one profitable drug.
Even in developed countries there is a huge potential for the development of nutraceuticals and pharmaceuticals from herbal materials.
For example the UK herbal materia medica contains around 300 species, whereas the Chinese herbal materia medica contains around 7,000 species.
Even up to the beginning of twentieth century, pharmacognosy was more of a descriptive subject akin mainly to botanical science, and it consisted of identification of drugs both in entire and powdered conditions and concerned with their history, commerce, collection, preparation and storage.
The development of modern pharmacognosy took place later during the period 1934–1960 by simultaneous application of disciplines like organic chemistry, biochemistry, biosynthesis, pharmacology and modern methods and techniques of analytic chemistry, including paper, thin layer, and gas chromatography and spectrophotometry
The substances from the plants were isolated like
Quinine and caffeine (1820)
Their structures were elucidated and pharmacological active constituents studied.
The development was mainly due to the following four events:
1. Isolation of penicillin in 1928 by William Fleming and large-scale production in 1941 by Florey and Chain.
2. Isolation of resperpine from rauwolfia roots and con-firming its hypotensive and tranquilizing properties.
3. Isolation of vinca alkaloids, especially vincristine and vinblastine. Vincristine was found useful in the treatment of leukaemia. These alkaloids also have anticancer properties.
4. Steroid hormones like progesterone were isolated by partial synthesis from diosgenin and other steroid saponins by Marker’s method. Cortisone and hydro-cortisone are obtained from progesterone by chemical and microbial reaction.
This period can also be termed antibiotic age, as besides penicillin, active antibiotics like streptomycin, chloramphenicol, tetracycline and several hundred antibiotics have been isolated and studied extensively.