Plants
have the ability to synthesize a wide variety of chemical compounds that are
used to perform important biological functions, and to defend against attack
from predators such as insects, fungi and herbivorous mammals. Many of these phytochemicals have beneficial effects on long-term health when
consumed by humans, and can be used to effectively treat human diseases. At
least 12,000 such compounds have been isolated so far; a number estimated to be
less than 10% of the total.[1][2] These phytochemicals are divided into (1) primary metabolites such as sugars and fats, which are found in all plants; and (2) secondary metabolites – compounds which are found in a smaller range of plants, serving
a more specific function.[3] For example, some secondary metabolites are toxins used to deter predation and others are pheromones used to attract insects for pollination. It is these secondary metabolites and pigments
that can have therapeutic actions in humans and which can be refined to produce
drugs—examples are inulinfrom the roots of dahlias, quinine from the cinchona, morphine and codeine from the poppy, and digoxin from the foxglove.[3] Chemical compounds in plants mediate their
effects on the human body through processes identical to those already well
understood for the chemical compounds in conventional drugs; thus herbal
medicines do not differ greatly from conventional drugs in terms of how they
work. This enables herbal medicines to be as effective as conventional
medicines, but also gives them the same potential to cause harmful side
effects.[1][2]
Most
cultures have a tradition of using plants medicinally. In Europe, apothecaries stocked herbal ingredients for their medicines.
In the Latin names for plants created by Linnaeus,
the word officinalis indicates that a plant was used in this way. For
example, the marsh mallow has the classificationAlthaea
officinalis, as it was traditionally used as an emollient to soothe ulcers.[4] Ayurvedic
medicine, herbal medicine and traditional Chinese medicine are other examples of medical practices that incorporate medical
uses of plants. Pharmacognosy is the branch of modern medicine about medicines
from plant sources. Plants included here are those that have been or are being
used medicinally, in at least one such medicinal tradition.
Modern
medicine now
tends to use the active ingredients of plants rather than the whole plants. The phytochemicals may be synthesized,
compounded or otherwise transformed to makepharmaceuticals. Examples of such
derivatives include Digoxin,
from digitalis; capsaicine,
from chili; and aspirin, which is chemically
related to the salicylic
acid found
in white
willow. The opium poppy continues to be a major industrial source of opiates,
including morphine. Few traditional remedies,
however, have translated into modern drugs, although there is continuing
research into the efficacy and possible adaptation of traditional herbal
treatments