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UNIT-I Introduction to Pharmacognosy:

  • The word 'pharmacognosy' had its introduced in the early 19th century to designate the discipline related to medicinal plants.
  • It is derived from the Greek word pharmakon, a drug, and gignosco. "to acquire a knowledge of and as recorded by Dr K. Ganzinger.
  • The terms 'pharmacognosy and pharmacodynamics were probably first coined by Johann Adam Schmidt (1759-1809) in his hand-written manuscript Lehrbuch der Materia Medica, which was posthumously published in Vienna in 1811.

Definition :- 

Pharmacognosy is the study of medicines derived from natural sources. The American Society of Pharmacognosy defines it as 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.

History:-

ANCIENT INDIA

  • In India knowledge of medicinal plants is very old, and medicinal properties of plants are described in Rigveda and in Atharvaveda (3500-1500 B.C.) from which Ayurveda has developed.
  • The basic medicinal texts in this world region. The Ayurvedic writings can be divided in three main ones (Charaka Samhita. Susruta Samhita, Astanga Hrdayam Samhita) and three minor ones (Sarngadhara Samhita, Bhava Prakasa Samhita, Madhava Nidanam Samhitai.
  • Ayurveda is the term for the traditional medicine of ancient India. "Ayur" means life and "veda" means the study of which is the origin of the term.

ANCIENT EGYPT

  • The most complete medical documents existing are the Ebers Papyrus (1550 B.C.), a collection of 800 prescriptions, mentioning 700 drugs.
  • The Edwin Smith Papyrus (1600 B.C.), which contains surgical instructions and formulas for cosmetics.
  • The Kahun Medical Papyrus is the oldest-it comes from 1900 B.C. and deals with the health of women, including birthing instructions.

ANCIENT CHINA

  • The most important clinical manual of traditional Chinese medicine is the Shang Hang Lun (Treatise an the Treatment of Acute Diseases Caused by Cold) written by Chàng Chung-Chúng 142220). The fame and reputation of the Shang Han Lun as well as its companion book. Chin Kuei Yao Luch (Prescriptions from the Golden Chamber), is the historical origin of the most important classical herbal formulas that have become the basis of Chinese and Japanese Chinese herbalism (called Kampo)
  • Shen Nung (about 2700 B.C.) has written the first Pen T-Sao, or Native Herhal, recording 365 drugs.
  • These were subdivided as follows: 120 emperor herbs of high, food grade quality which are non-toxic and can be taken in large quantities to maintain health over a long period of time, 120 minister herbs, some mildly toxic and some not, having stronger therapeutic action to heal diseases and finally 125 servant herbs that having specific action to treat disease and eliminate stagnation.

ANCIENT GREECE AND ROME

  • Hippocrates (460-370 B.C.) is referred to as father of medicine.
  • Dioscorides, a physician who lived in the first century A.D., described medicinal plants, some of which like belladonna, ergot, opium, and colchicum are used even today.
  • Pliny wrote 37 volumes of natural history and Galen (131-A.D. 200) devised methods of preparations of plant and animal drugs, known as 'galenicals' in his honour.


SCOPE OF PHARMACOGNOSY

The scope of Pharmacognosy is described in the following areas:

1. Medical ethnobotany: the study of the traditional use of plants for medicinal purposes.

2. Ethnopharmacology: the study of the pharmacological qualities of traditional medicinal substances.

3. The study of phytotherapy (the medicinal use of plant extracts); and Phytochemistry, the study of chemicals derived from plants (including the identification of new drug candidates derived from plant sources).

4. Zoopharmacognosy: the process by which animals self-medicate, by selecting and using plants, soils. and insects to treat and prevent disease.

5. Marine pharmacognosy: the study of chemicals derived from marine organisms.


DEVELOPMENT IN PHARMACOGNOSY

1. Le'mery (1645-1715) Importance of Extraction method.

2. William Withering (1785) Medicinal properties of Foxglove leaves.

3. Derosne (1803) Isolated narcotin from opium.

4. Stass and Otto (1852) new extraction process for Alkaloids.

5. Posselt & Reimann (1828) Nicotine from tobacco.

6. Neumann (1860) Cocaine.


Source of Drugs:-

(A). Plant source

These are oldest known sources of drugs. All plant contains some therapeutically active constituents in their different specific parts and used as a source of drug i.e.

• Leaf: Belladona

• Root: Rauwolfia

• Flower: Saffron

• Bark: Cinchona

• Seed: Nux-vomica

• Stem: Ephedra

Plant source contains many phytoconstituents, which are responsible for therapeutic activity.i.e.

  • Alkaloids: Pilocorpin, Quinine.
  • Glycoside: Digoxin, Sennoside.
  • Fixed oil: Castor oil. Olive oil.
  • Volatile oil: Rose oil, Lemon grass oil.
  • Carbohydrates: Glucose, Starch.
  • Gums/Mucilage: Acacia, Guar gum. Tragacanth.

(B). Animal Sources

  • Many therapeutically active lead compounds obtained from animals i.e.
  • In older days dried toad skin was used to treat toothache and bleeding of gum.
  • In recent time insulin is prepared from animal sources i.e. Bovine insulin from cow and buffalo, porcine insulin from pork.
  • Venoms and toxins have been used as lead compounds in the development of novel drugs Eg.: Teprotide, a peptide isolated from the venom of the Brazilian viper, was the lead compound for the development of the antihypertensive agent's captopril.

(C). Microbiological Sources

Some microbes are used to produce therapeutically active lead compounds or antibiotics. Fungi are mainly used to produce antibiotics.

  • Penicillin from Penicillium notatum.
  • Streptomycin from Streptomyces griseus.

(D). MARINE SOURCES

70% of the world is surrounded by water but the useful drugs from marine sources are not that much explored. Some marine drugs are given below:

• Cod liver oil, Shark liver oil, Sodium alginate.

• Many novel drugs are obtained from marine sources which give antiviral, antibacterial, antihypertensive or antitubercular effect.

(E). MINERAL SOURCES

Some natural drugs obtained from minerals and few minerals are used for treatment of many diseased conditions.

e.g. Shilajit, calamine, aluminium hydroxide, bentonite, prepared chalk, barium sulphate, kieselguhr (diatomaceous earth), iron, gold etc.

(F). PLANT TISSUE CULTURE

• It is a technique by which plant cells, tissues or organs are grown on artificial nutrient medium, either static or liquid, under aseptic and controlled conditions.

• Since last 20 years researchers are doing their research on biosynthetic methods for production of secondary metabolites for some plants. It is very beneficial to increase the percentage of phytoconstituents i.e. Diosgenin from Dioscorea deltoidea.

• Diosgenin is highly useful for synthesis of steroids. When diosgenin is isolated from naturally occurring plants, it will take 5 to 6 year for complete maturation of plant.

• When diosgenin is produced by plant tissue culture method it will take very less time and yield value of diosgenin is increased (i.e-7-8%).



Classification of Drugs of Natural Origin

  • Crude drugs can be regarded as the substances either used directly or indirectly as a drug which have not been changed or modified in its chemical composition.
  • The crude drugs of natural origin can be divided into two main categories as organized crude drugs and unorganized crude drugs.

1. Organized drugs:-

Organized drugs consist of the cellular organization in the form of anatomical features. These are mostly the crude drugs from plant sources. Almost all of the morphological plant parts or the entire plant itself can be called as an organized drug.

Examples: Cinchona bark. Sandalwood. Quassia wood. Senna, Digitalis leaves. Nux vomica seeds. Rauwolfia roots.

2. Unorganized drugs 

The unorganized drugs do not have the morphological or anatomical organization as such. These are the products which come directly in the market but their ultimate source remains the plants. animals or minerals Microscopical studies are not required for such crude drugs. 

Examples: Plant exudates as dried latex, dried juices, dried extracts, gums and mucilages, oleoresins and oleo- gum -resins.



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