Medicinal plants (реферат)

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Medicinal plants

Herbalism, also known as phytotherapy, is folk and traditional
medicinalpractice based on the use of plantsand plant extracts.

Finding healing powers in plants is an ancient idea. People in all
continents have long used hundreds, if not thousands, of indigenous
plants, for treatment of various ailments dating back to prehistory.
There is evidence that Neanderthals living 60,000 years ago in
present-day Iraq used plants for medicinal purposes. These plants are
still widely used in ethnomedicine around the world.

Plants have an almost limitless ability to synthesize aromatic
substances, most of which are phenols or their oxygen-substituted
derivatives such as tannins. Most are secondary metabolites, of which at
least 12,000 have been isolated, a number estimated to be less than 10%
of the total. In many cases, these substances serve as plant defense
mechanisms against predation by microorganisms, insects, and herbivores.
Many of the herbs and spices used by humans to season food yield useful
medicinal compounds.

The use and search for drugs and dietary supplements derived from plants
have accelerated in recent years. Pharmacologists, microbiologists,
botanists, and natural-products chemists are combing the Earth for
phytochemicals and leads that could be developed for treatment of
various diseases.–Dr M Tariq Salman 19:06, 30 January 2006 (UTC)

The use of herbsto treat diseaseis almost universal among
non-industrialized societies. A number of traditions came to dominate
the practise of herbal medicine in the Western worldat the end of the
twentieth century:

The Western, based on Greekand Romansources,

The Ayurvedicfrom India, and

Chinese herbal medicine(Chinese herbology).

Many of the pharmaceuticalscurrently available to Western physicians
have a long history of use as herbal remedies, including opium, aspirin,
digitalis, and quinine.

Biological background

All plants produce chemical compoundsas part of their normal
metabolicactivities. These can be split into primary metabolites, such
as sugarsand fats, found in all plants, and secondary metabolites found
in a smaller range of plants, some only in a particular genusor species.

The autologousfunctions of secondary metabolites are varied. For
example, as toxinsto deter predation, or to attract insects for
pollination. It is these secondary metabolites which can have
therapeutic actions in humans and which can be refined to produce drugs.
Some examples are inulinfrom the roots of dahlias, quininefrom the
cinchona, morphineand codeinefrom the poppy, and digoxinfrom the

As of 2004, the National Center for Complementary and Alternative
Medicine started to fund clinical trialsinto the effectiveness of herbal

Some surveys of scientific herbal medicine can be found in
Evidence-based herbal medicine edited by Michael Rotblatt, Irwin Ziment;
Philadelphia: Hanley & Belfus, 2002, and Herbal and traditional
medicine: molecular aspects of health, edited by Lester Packer, Choon
Nam Ong, Barry Halliwell; New York: Marcel Dekker, 2004.


A survey released in May 2004 by the National Center for Complementary
and Alternative Medicinefocused on who used complementary and
alternative medicines(CAM), what was used, and why it was used. The
survey was limited to adults age 18 years and over during 2002 living in
the United States. According to this recent survey, herbal therapy, or
use of natural products other than vitaminsand minerals, was the most
commonly used CAM therapy (18.9%)when all use of prayerwas excluded.


Examples of some commonly used herbal medicines:

Artichokeand several other plants reduced total serum cholesterollevels
in preliminary studies.

Black cohoshand other plants that contain phytoestrogens(plant molecules
with estrogenactivity) have some benefits for treatment of symptoms
resulting from menopause.

Echinaceaextracts limit the length of coldsin some clinical trials,
although some studies have found it to have no effect.

Garliclowers total cholesterol levels, mildly reduces blood pressure,
reduces platelet aggregation, and has antibacterialproperties.

St John’s wortis more effective than a placebofor the treatment of mild
to moderate depressionin some clinical trials.

Peppermint teafor problems with the digestive tract, including irritable
bowel syndromeand nausea.

Nigella sativa(Black cumin)is a generalist medicinal plant used for
diverse ailments such as cough, pulmonary infections, asthma, influenza,
allergy, hypertension and stomach ache. The seeds are considered
carminative, stimulant, diuretic and galactogogue. It is often taken
with honey. Seed powder or oil is externally applied for eruptions of


A common misconception about herbalism and the use of ‘natural’ products
in general, is that ‘natural’ equals safe. Nature, however, is not
benign, and many plants have chemical defence mechanisms against
predators that can have adverse effects on humans. Examples are poison
hemlockand nightshade, which can be deadly. Herbs can also have
undesirable side-effects just as pharmaceutical products can. These
problems are exacerbated by lack of control over dosage and purity.

Name confusion

The common names of herbs may be shared with others with different
effects. For example, in one case in Belgiumin a TCM-remedy for losing
weight, one herb was swapped for another resulting in kidneydamage. One
variety of the herb causes elevated blood pressure and increased heart
rate, versus another variety for the weight-loss remedy, the varieties
are differentiated by the suffix in the Latinnames.

International standards

The legal status of herbal ingredients varies by country. For example,
Ayurvedicherbal products often contain levels of heavy metals that are
considered unsafe in the US, but heavy metals are considered therapeutic
in Ayurvedic medicine.

Medical interaction

Those wishing to use herbal remedies should first consult with a
physician, as some herbal remedies have the potential to cause adverse
drug interactions when used in combination with various prescription and
over-the-counterpharmaceuticals. Dangerously low blood pressure may
result from the combination of an herbal remedy that lowers blood
pressure together with prescription medicine that has the same effect.
Physicians may not be the best sources of information because most have
no knowledge of herbal medicine. There is little known about
interactions of herbal remedies with pharmaceuticals because, contrary
to pharmaceutical medicine, there is no official system, database, or
hotline to report and publish adverse interactions, so even herbalists
may not be aware of adverse interactions.

To put the safety issue in perspective, an editorial in the British
Medical Journalpointed out, “Even though herbal medicines are not devoid
of risk, they could still be safer than synthetic drugs. Between 1968and
1997, the World Health Organization’s monitoring center collected 8985
reports of adverse events associated with herbal medicines from 55
countries. Although this number may seem impressively high, it amounts
to only a tiny fraction of adverse events associated with conventional
drugs held in the same database.” (BMJ, October 18, 2003; 327:881-882).

A meta-analysis published in the Journal of the American Medical
Association(JAMA) reported the following: “The overall incidence of
serious adverse drug reactions (ADRs) was 6.7% (95% confidence interval
[CI], 5.2%-8.2%) and of fatal ADRs was 0.32% (95% CI, 0.23%-0.41%) of
hospitalized patients. We estimated that in 1994overall 2,216,000
(1,721,000-2,711,000) hospitalized patients had serious ADRs and 106,000
(76,000-137,000) had fatal ADRs, making these reactions between the
fourth and sixth leading cause of death.” (JAMA. 1998;279:1200-1205)


NIH Institute and Center Resources, National Institute of Health.

More Than One-Third of U.S. Adults Use Complementary and Alternative
Medicine, National Center for Complementary and Alternative Medicine
Press release. May 27, 2004.

Herbs for serum cholesterol reduction: a systematic view, Thompson Coon

L –







Natural Products Discussion GroupInternet discussion group on the
science and folklore of herbal medicines and natural

Retrieved from “http://en.wikipedia.org/Herbalism”

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