Herbalism is a
traditional medicinal or folk medicine practice based on the use of
plants and plant extracts. Herbalism is also known as botanical
medicine, medical herbalism, herbal medicine, herbology, herblore,
and phytotherapy. The scope of herbal medicine is sometimes extended
to include fungal and bee products, as well as minerals, shells and
certain animal parts. Pharmacognosy is the study of medicines
derived from natural sources.
Traditional use of medicines is recognized as a way to learn about
potential future medicines. In 2001, researchers identified 122
compounds used in mainstream medicine which were derived from "ethnomedical"
plant sources; 80% of these compounds were used in the same or
related manner as the traditional ethnomedical use.
Plants have evolved the ability to synthesize chemical compounds
that help them defend against attack from a wide variety of
predators such as insects, fungi and herbivorous mammals. By chance,
some of these compounds, whilst being toxic to plant predators, turn
out to have beneficial effects when used to treat human diseases.
Such secondary metabolites are highly varied in structure, many are
aromatic substances, most of which are phenols or their
oxygen-substituted derivatives. At least 12,000 have been isolated
so far; a number estimated to be less than 10% of the total.
Chemical compounds in
plants mediate their effects on the human body by binding to
receptor molecules present in the body; such processes are identical
to those already well understood for conventional drugs and as such
herbal medicines do not differ greatly from conventional drugs in
terms of how they work. This enables herbal medicines to be in
principle just as effective as conventional medicines but also gives
them the same potential to cause harmful side effects. Many of the
herbs and spices used by humans to season food yield useful
Similarly to prescription drugs, a number of herbs are thought to be
likely to cause adverse effects. Furthermore, "adulteration,
inappropriate formulation, or lack of understanding of plant and
drug interactions have led to adverse reactions that are sometimes
life threatening or lethal.