2. Importance of plants as a source of new drugs
The development of traditional medicinal systems incorporating
plants as means of therapy can be traced back to the Middle
Paleolithic age some 60,000 years ago as found from fossil
studies [7]. In recent times, developed countries are turning to
the use of traditional medicinal systems that involve the use of
herbal drugs and remedies18 and according to the World Health
Organization (WHO), almost 65% of the world’s population
has incorporated the value of plants as a methodology of
medicinal agents into their primary modality of health care . It is
often noted that 25% of all drugs prescribed today come from
plants [8], [9]
.
This estimate suggests that plant-derived drugs make up a
significant segment of natural product– based pharmaceuticals. Out
of many families of secondary metabolites, or compounds on
which the growth of a plant is not dependent, nitrogencontaining
alkaloids have contributed the largest number of
drugs to the modern pharmacopoeia, ranging in effects from
anticholinergics (atropine) to analgesics (opium alkaloids) and
from antiparasitics (quinine) to anticholinesterases
(galantamine) to antineoplastics (vinblastine/vincristine) [10]
.
Although not as plentiful as alkaloids in the modern
pharmacopoeia, terpenoids (including steroids) have made an
equally important contribution to human health. They range from
Na+/K+ Na+ K+ pump- inhibiting cardiac glycosides from
Digitalis spp [11]
, antineoplastic paclitaxel to antimalarial
artemisinin. To anti-inflammatory triptolide