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Drugs from plants:
* Medicinal plants have been used as a major source of drugs
for thousands of years in human history, and even today they are
basis of the systematic traditional medicine practices in many
countries all over the world.
* The first recorded literature on medicinal plants can be traced back
to an earlier age of human history, such as the Ayurveda (2000 BC) in
India, the Divine Farmer’s Herb- Root Classic (3000 BC) in China, and the
Ebers Papyrus (1550 BC) in Egypt.
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It is evident that the modern drug industry has been
developed to a considerable degree as a result of plant-based
traditional medicines.
A review published in 2001 indicated that 88 active
compounds isolated from 72 medicinal plants have been
introduced into modern drug therapy, with many of them being
considered as the active principle responsible for their ethno
pharmacological use.
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Bases of plant Selection:
* Biodiversity Prospective:
The number and variety of plants found within a specified geographic region.
* Screening as much samples as possible for specified biological activities.
* Collect as much as possible. About 5- 15% from plant species were screened.
Estimated 300,000 to 500,000 are present.
* Ethnobotany (Ethnopharmacology) Prospective:
In this approach drug discovery is guided by the impressive quantity and
quality of information of indigenous cultures that have used plants and animal
products to control disease and injury.
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This information is passed from generation to generation
through oral history and it is necessary to record and
validate the knowledge of the shaman before it is lost
forever.
•Collection based on Folk uses of samples.
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Examples of drugs derived from plants:
•
Morphine.
Morphine was first isolated in 1806 and manufacturing of an
analgesic drug was realized by E. Merck , Germany in 1826.
Morphine
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Papaver somniferum
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Some of these plant-derived therapeutic agents, such as
atropine (anticholinergic) from Atropa belladonna, codeine (cough
suppressant) from papaver somniferum, colchicine (antigout),
ephedrine (bronchodilator), morphine (analgesic).
Codeine
Atropine
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Quinine.
Quinine was isolated as pure active principle as antimalaria in 1820,
representing the only active antimalaria medicine until the introduction of
the synthetic drug pamaquine, the later with severe side effects.
CH3
CH3
N
HN
N
H3CO
Quinine
Pamaquine
CH3
•
Acetylsalicylic acid.
• The bark of Willow-tree was known for its analgesic and
antipyretic properties for more than 2000 years by Greeks and
the Roman.
• In 1850’s Salicin was isolated as the active principle of the bark,
salicin ( beta glucoside of salicylic alcohol).
• Degradation of Salicin led to the discovery of Salicylic acid as
analgesic and antipyretic. It was commercialized in 1859.
•
Due to the gastric disorders of salicylic acid, efforts to reduce
the side effects resulted in acetylsalicylic acid which was
introduced to the market under the trade name Aspirin in 1899 by
Bayer.
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HO
H3C
O
O
HOOC
HOOC
Salicin
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salicylic acid
Acetylsalicylic acid
(Aspirin )
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Anticancer drugs from plants:
The example of anticancer drugs taxol was discovered at the
US National Center Institute in the late 1960s in the course of an in
vitro antitumor drug discovery program using human tumor cell
lines.
Screening of more than 110,000 samples derived from more
than 35,000 plant genera collected worldwide resulted in the isolation
and structure elucidation of taxol from the bark of the North
American yew tree Taxus brevifolia.
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Taxus brevifolia
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Semisynthetic Derivative:
Docetaxel (trade name Taxotere) is a clinically well established
anti-mitotic chemotherapy medication used mainly for the treatment
of breast, ovarian, and non-small cell lung cancer.
Docetaxel has an approved claim for treatment of patients, who
have locally advanced, or metastatic breast or non small-cell lung
cancer who have undergone anthracycline-based chemotherapy and
failed to stop cancer progression or relapsed.
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Administered as a one-hour infusion every three weeks
generally over a ten cycle course, docetaxel is considered as or
more effective than doxorubicin, paclitaxel and fluorouracil as a
cytotoxic antimicrotubule agent.
Docetaxel is marketed worldwide under the name Taxotere
by Sanofi-Aventis. Annual sales approx $2bn. Patent expires in
2010.
Taxol
Taxotere
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References:
1- Cutler, Stephen J.; Cutler, Horace G. (2000). Biologically active natural
products: pharmaceuticals. CRC Press. p. 5. ISBN 9780849318870.
2- Newman DJ, Cragg GM Natural products as sources of new drugs over the
last 25 years. Journal of Natural Products 70, 461-477 (2007).
3- Dan Bensky, Steven Clavey, Erich Stoger, and Andrew Gamble Chinese Herbal
Medicine: Materia Medica, Third Edition 2004
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