Abstract:
Plants have been used successfully for centuries by herbalists all over the world and
especially in Africa, Asia and Latin America for the treatment of various human diseases.
It has been estimated that 80% of people living in developing countries are almost completely
dependent on traditional medical practices for their primary health care needs (Farnsworth
1990; Nwosu and Okafor 1995). Higher plants are known to be the main source of drug
therapy in traditional medicine.
Out of the 250 000 species of higher plants known to exist on earth, only a relative handful
have been thoroughly investigated for their therapeutic values. Yet, in terms of the quantity
consumed, the plant kingdom has yielded more than 25 % of the drugs used in prescriptive
medicines today (Farnsworth 1988; Balick 1990). On the basis of global survey data it has
been discovered that about 119 plant-derived chemical compounds of known structure are
currently used as drugs or as biodynamic agents that affect human health. Less than a dozen
of these are produced- commercially by synthesis or by simple chemical modification of the
extracted active compounds; the remainder are extracted and purified directly from plants.
These 119 useful drugs are obtained from only about 90 species of plants (Farnsworth et al.
1985; Farnsworth 1990).
Considering the current rate of deforestation and concurrent loss of biodiversity throughout
the world, there is an urgent need to examine the rest of the plant kingdom for new
pharmaceutical compounds.
