Introduction to Pharmacognosy

Definition, history, scope,  Sources of Drugs,

Organized, unorganized

As per PCI Syllabus
(S. Y. B. Pharm Sem –VI)  Unit-I

Introduction


Pharmacognosy is concerned with the knowledge of crude drugs obtained from natural origin. Pharmacognosy has a long history i.e. 3500 B.C.
Most of the world's population relies upon natural plants for cure of ailments. Phytoconstituents present in the medicinal plants are responsible for the pharmacological activity.
These phytoconstituents can be classified on the basis of their chemical moiety.The phytoconstituents are extracted through extraction method.

The word Pharmacognosy is derived from two Greek words “Pharmakon” means drug and “Gignosis” means to acquire knowledge of.
The term Pharmacognosy was introduced by C.A. Seydler, a medical student in Halle Salle, Germany in the year 1815.

Number of definitions for the term Pharmacognosy are used

i) Pharmacognosy is defined as scientific and systematic study of structural, physical, chemical and biological characters of crude drugs along with their history, method of cultivation and collection and preparation for market.

ii) Pharmacognosy may be defined as an applied science that deals with the biological, biochemical and economic features of natural drugs and their constituents.

iii) Pharmacognosy is the study of drugs that originate from the plants and animal kingdom

iv. Pharmacognosy is the study of medicinal drugs derived from plants or other natural sources.
The American Society of Pharmacognosy defines pharmacognosy as "the study of the physical, chemical, biochemical and biological properties of drugs, drug substances or potential drugs or drug substances of natural origin as well as the search for new drugs from natural sources".
It is also defined as the study of crude drugs.

Crude drugs: It is used for those natural products such as plants or part of plants, extracts and exudates which are not pure compounds.

Ethnobotany: It is a broad term referring to the study of plants by humans.

Ethnomedicine: It refers to the use of plants by humans as medicine.

Traditional medicine: It is the sum total of all non-mainstream medical practices, usually excluding so called “western” medicine.

—Natural products: they can be
Entire organism (plant, animal, organism)
Part of an organism (a leaf or flower of a plant, an isolated gland or other organ
of an animal)
An extract or an exudate of an organism
Isolated pure compounds


History of Pharmacognosy


The history of herbal medicines is as old as human civilization. Indian history of medicinal plants is taken back from 3500 B.C. A large portion of Indian population depends upon Indian system of medicine.
i.e. Ayurveda which have well known treatise in Charaka Samhita and Sushrutha Samhita.



Father of  medicines : Hippocrats (460-360 B.C.)
Study of Animal Kingdom: Aristottle  (384-322  B.C.)
Study on Plant  Kingdom : Theophrastus (372-287 B.C.)
Compiled 37 volumes of  natural history.: Pliny Elder (23-70 A.D.)
Introduced Galenical Pharmacy: Galen (131 - 200 A.D.)
Discovered the term ‘Pharmacognosy’: Seydler  (1815)
Published medicinal properties of fox glove: William Withering (1785)
Gave a number of extraction procedures: Stass and Otto (1852) 

Modern Age

The earliest books containing descriptions of drugs related to as "Materia Medica" were called "Herbals“

e.g. "Ortis Sanitatis" 1485, meaning garden of health written in Latin and Published in 1491 in Mainz and containing items from mineral, animal and vegetable origin arranged alphabetically.

Before the study of drugs was systematized, they were commonly described as independent units and for case of reference were arranged alphabetically under the great divisions of minerals, plants & animals. 

Scope of Pharmacognosy

Pharmacognosy as an applied science which played a crucial role in the development of different disciplines of science.
The knowledge of plant taxonomy, breeding, pathology and plant genetics is helpful in the development of different disciplines of science. The technology involving extraction, purification, and characterization of pharmaceuticals from natural resources has signified contribution to the advancement of natural and physical sciences.

Pharmacognosy is the infrastructure on which depends evolution of noble medicines. Further, crude drugs also provide essential intermediates for final synthesis of active compounds. India is the richest source of medicinal plants which are distributed in almost all parts of the country.

To scope up with the demand of constant supply for the phytochemical industries, the domestication and cultivation of some of the important plants are necessary. There are many drugs which are imported to India like Balsam of Tolu, Benzoin, Asafoetida etc.

If the cultivation is carried out in India, sufficient amount of foreign exchange can be saved. There are number of diseases for which modern medicine have no cure like stress, genetic diseases, arthritic diseases, liver disorder, cancer and AIDS etc.

In such cases, only symptoms are treated to provide relief to the patients. But plant drugs from pharmacognosy have answers to such questions i.e. by use of plant drugs, we can treat incurable diseases.
In this way, pharmacognosy has a wide scope in different areas to save mankind.

Pharmacognosy is important branch of pharmacy which is playing key role in new drug discovery and development by using natural products.
Pharmacognosy has given many leads for new drug discovery and development.

It is an important link between modern medicine systems (allopathy) and traditional system of medicine.
It is part medicinal system which is affordable as well as accessible to common man, As part of integrative system of medicine, pharmacognosy can help to increase effectiveness of modem medicine system.

It is acting as bridge between pharmacology, medicinal chemistry and pharmacotherapeutics and also pharmaceutics. It also bridges pharmaceutics with other pharmacy subjects.
More than 60 percent of world population is still using natural product for their primary healthcare needs. Pharmacognosy can provide safe and effective drugs in combination with modern medicine system.


1. Plant Sources

The use of plants as medicines has a long history in the treatment of various diseases.
The plant-derived compounds have a long history of clinical use, better patient tolerance and acceptance.
Plant source is the oldest source of drugs.
Most of the drugs in ancient times were derived from plants. Almost all parts of the plants are used i.e. leaves, stem, bark, fruits and roots.

i. Leaves

a.The leaves of Digitalis Purpurea are the source of Digitoxin and Digoxin, which
are cardiac glycosides
b.Leaves of Eucalyptus give oil of Eucalyptus, which is important component of
cough syrup.
c.Tobacco leaves give nicotine.
d.Atropa belladonna gives atropine

ii. Flowers

Poppy Papaver somniferum gives morphine (opoid).
Vinca rosea gives vincristine and vinblastine.
Rose gives rose water used as tonic.

iii. Fruits
Senna pod gives anthracine, which is a purgative (used in constipation).
Calabar beans gives physostigmine, which is cholinomimetic agent.

iv. Seeds
Seeds of Nux Vomica give strychnine, which is a CNS stimulant.
Castor oil seeds give castor oil.
Calabar beans give Physostigmine, which is a cholinomimetic drug.

v. Roots
Ipecacuanha root gives Emetine, used to induce vomiting as in accidental poisoning. It also has amoebicidal properties.
Rauwolfia serpentina gives rescrpine, a hypotensive agent.
Reserpine was used for hypertesion treatment.

vi. Bark
Cinchona bark gives quinine and quinidine, which are antimalarial drugs. Quinidine also has antiarrythmic properties.
Atropa belladonna gives atropine, which is anticholinergic.
Hyoscyamus Niger gives Hyosine, which is also anticholinergic.

vii. Stem
Chondrodendron tomentosum gives tuboqurarine, which is skeletal muscle relaxant used in general anesthesia.

2. Animal Sources

Pancreas is a source of Insulin, used in treatment of Diabetes.
Urine of pregnant women gives human chorionic gonadotropin (hCG) used for the treatment of infertility.

Sheep thyroid is a source of thyroxin, used in hypertension.
Cod liver is used as a source of vitamin A and D.

Anterior pituitary is a source of pituitary gonadotropins, used in treatment of infertility.
Blood of animals is used in preparation of vaccines.

Stomach tissue contains pepsin and trypsin, which are digestive juices used in treatment of peptic diseases in the past. Nowadays better drugs have replaced them.

3. Mineral Sources

i. Metallic and Non Metallic Sources

Iron is used in treatment of iron deficiency anemia.
Mercurial salts are used in Syphilis.
Zinc is used as zinc supplement. Zinc oxide paste is used in wounds and in eczema.
Iodine is antiseptic. Iodine supplements are also used.
Gold salts are used in the treatment of rheumatoid arthritis.

ii. Miscellaneous Sources

Fluorine has antiseptic properties.
Borax has antiseptic properties as well.
Selenium as selenium sulphide is used in anti dandruff shampoos.
Petroleum is used in preparation of liquid paraffin.
Shilajeet, calamine clay are some of the examples of mineral origin drugs.

4. Synthetic/ Semi synthetic Sources

i. Synthetic Sources: When the nucleus of the drug from natural source as well as its chemical structure is altered it synthetic.

Examples include Emetine Bismuth Iodide.

ii. Semi Synthetic Source: When the nucleus of drug obtained from natural source is retained but the chemical structure altered, we call it semi-synthetic.

Examples include Apomorphine, Diacetyl morphinc, Ethinyl Estradiol. Homatropinc, Ampicillin and Methyl testosterone.
Most of the drugs used nowadays (such as antianxiety drugs, anti convulsants) are synthetic forms.

5. Microbiological Sources

Penicillium notatum is a fungus which gives penicillin.
Actinobacteria give Streptomycin.
Aminoglycosides such as gentamicin and tobramycin are obtained from streptomycis and micro-monosporas.

6. Recombinant DNA Technology
Recombinant DNA technology involves cleavage of DNA by enzyme restriction endo-nuclcases.
The desired gene is coupled to rapidly replicating DNA (viral, bacterial or plasmid).
The new genetic combination is inserted into the bacterial cultures which allow production of vast amount of genetic material.

Advantages

1. Huge amounts of drugs can be produced.
2. Drug can be obtained in pure form.
3. It is less antigenic.

Disadvantages

1. Well equipped lab is required.
2. Highly trained staff is required.
3. It is a complex and complicated technique.

CRUDE DRUG

i.Organised drug
ii.Unorganised drug
i. Organised drugs

The crude drug are grouped as organized and unorganized drugs. Organised drugs are the drug having the crude drug material which represent plant parts and having cellular structure.


ii. Unorganised drugs

Unorganised drugs are materials having a structure that is fairly uniform throughout and are not composed of cells.
They are usually derived from parts of plants of animals by some process of extraction, such as incision.

e.g. opium, decoction e.g., agar, expression eg. olive oil, or natural secretions such as beeswax and myrrh.


Classification of Unorganized Drugs


based upon their origin and nature:

a) Latex e.g., opium.
b) Dried juice e g., Aloes
c) Extracts e.g., catechu.
d) Saccharine substances e.g., Honey.
e) Oil and fats e.g., castor oil and lard.
f) Gums e.g., gum Acacia.
g) Resins e.g., colophony.
h) Waxes e.g., beeswax.
i) Volatile oils e.g., cinnamon oil.