Pharmaceutical drugs
Many pharmaceutical drugs used in western medicine are made from plants or the properties of plants have inspired their development (Sheldon et al., 1997). Among the early isolates were morphine from Papaver somniferum (1803), strychnine from Strychnos nux-vomica (1818), quinine from Cinchona (1821) and codeine from Papaver somniferum (1837).
Yew Taxus bacatta
©Alan Hamilton
In the USA, 25% of all prescriptions dispensed from community pharmacies between 1959 and 1980 contained plant extracts or active principles prepared from higher plants (Farnsworth et al., 1985).
A study of the top 150 proprietary drugs used in the USA in 1993 found that 57% of all prescriptions contained at least one major active compound that was either derived from or patterned after compounds from biological diversity (Grifo & Rosenthal 1997).
In some cases, chemicals extracted from plants are used directly as medicines, for example reserpine (lowers blood pressure, extracted from serpent-root Rauvolfia serpentina), ephedrin (a decongestant, from the shrub Ephedra), digitalin (used to treat irregularities in heart rhythm, from Foxglove Digitalis sp.), and vinblastine and vincristine (for treating childhood leukaemia and Hodgkin's disease, from the rosy periwinkle Catharanthus roseus).
In other cases, chemicals are extracted from plants and used as chemical building-blocks to create new compounds which are then used as drugs. The drugs etoposide and teniposide (used for treating skin cancers and warts) are manufactured from epipodophyllotoxin, a chemical found in May apple Podophyllum sp. Progesterone (used as an oral contraceptive) is manufactured from diosgenin, found in certain species of yam Dioscorea sp.
Some drugs, including some that are synthesised today from inorganic sources, were inspired in their historical development by the physiological activities of chemicals found in plants. Aspirin, which is today synthesized inorganically, was inspired in its development by folk uses of the bark of willow Salix to treat fever.
Although drugs extracted from or inspired by plants are used very extensively, the actual number of plant species that has contributed to western medicine is rather few - only 95 vascular plant species, as reported in 1991 (Farnsworth & Soejarto, 1991). Apart from plants sensu stricto, fungi play major roles in western medicine, notably through the use of genera such as Penicillium and Streptomyces as sources of antibiotics (developed in the 1940s).
Farnsworth, N.R., Akerele, & Bingel, A.S. (1985) Medicinal plants in therapy. Bull. World Health Organisation, 63, 965-981.
Farnsworth, N.R. & Soejarto, D.D. (1991). Global importance of medicinal plants. In The conservation of medicinal plants (eds O. Akerele, V. Heywood & H. Synge), pp. 25-51. Cambridge University Press, Cambridge, UK.
Grifo, F. & Rosenthal, J., eds. (1997) Biodiversity and human health. Island Press, Washington D.C., USA.
Sheldon, J.W., Balick, M.J., & Laird, S.A. (1997) Medicinal plants: can utilization and conservation coexist? Advances in Economic Botany, 12, 1-104.
