Sources of Drugs

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Drugs are substances that are used or intended to be used in the diagnosis, prevention, treatment or cure of diseases. In early times, these substances were derived from natural sources, of which plants took up the major share. With the introduction of technology, most drugs today are manufactured synthetically in the laboratory. The major sources of drugs can be grouped into the following

Drugs are obtained from six major sources:

  1. Plant sources
  2. Animal sources
  3. Mineral/ Earth sources
  4. Microbiological sources
  5. Semi synthetic sources/ Synthetic sources
  6. Recombinant DNA technology.

1. Plant Sources:

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.

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.

Flowers:
  1. Poppy papaver somniferum gives morphine (opoid)
  2. Vinca rosea gives vincristine and vinblastine
  3. Rose gives rose water used as tonic.

Photo of Papaver somniferum by Evelyn Simak

Fruits:
  1. Senna pod gives anthracine, which is a purgative (used in constipation)
  2. Calabar beans give physostigmine, which is cholinomimetic agent.
Seeds:
  1. Seeds of Nux Vomica give strychnine, which is a CNS stimulant.
  2. Castor oil seeds give castor oil.
  3. Calabar beans give Physostigmine, which is a cholinomimetic drug.
Roots:
  1. Ipecacuanha root gives Emetine, used to induce vomiting as in accidental poisoning. It also has amoebicidal properties.
  2. Rauwolfia serpentina gives reserpine, a hypotensive agent.
  3. Reserpine was used for hypertension treatment.
Bark:
  1. Cinchona bark gives quinine and quinidine, which are antimalarial drugs. Quinidine also has antiarrythmic properties.
  2. Atropa belladonna gives atropine, which is anticholinergic.
  3. Hyoscyamus Niger gives Hyosine, which is also anticholinergic.
Stem:

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

2. Animal Sources:

  1. Pancreas is a source of Insulin, used in treatment of Diabetes.
  2. Urine of pregnant women gives human chorionic gonadotropin (hCG) used for the treatment of infertility.
  3. Sheep thyroid is a source of thyroxin, used in hypertension.
  4. Cod liver is used as a source of vitamin A and D.
  5. Anterior pituitary is a source of pituitary gonadotropins, used in treatment of infertility.
  6. Blood of animals is used in preparation of vaccines.
  7. 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:
  1. Iron is used in treatment of iron deficiency anemia.
  2. Mercurial salts are used in Syphilis.
  3. Zinc is used as zinc supplement. Zinc oxide paste is used in wounds and in eczema.
  4. Iodine is antiseptic. Iodine supplements are also used.
  5. Gold salts are used in the treatment of rheumatoid arthritis.
ii. Miscellaneous Sources:
  1. Fluorine has antiseptic properties.
  2. Borax has antiseptic properties as well.
  3. Selenium as selenium sulphide is used in anti dandruff shampoos.
  4. Petroleum is used in preparation of liquid paraffin.

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, we call 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 is altered, we call it semi-synthetic.
Examples include Apomorphine, Diacetyl morphine, Ethinyl Estradiol, Homatropine, Ampicillin and Methyl testosterone.
Most of the drugs used nowadays (such as antianxiety drugs, anti convulsants) are synthetic forms.

5. Microbiological Sources:

  1. Penicillium notatum is a fungus which gives penicillin.
  2. Actinobacteria give Streptomycin.
  3. Aminoglycosides such as gentamicin and tobramycin are obtained from streptomycis and micromonosporas.

6. Recombinant DNA technology:

Recombinant DNA technology involves cleavage of DNA by enzyme restriction endonucleases. 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.
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