Sources of Drugs: Natural Origins

Study Notes

Natural sources are the oldest, including plants, animals, microorganisms, and minerals.

Various parts of plants provide important drugs:
- Leaves:
  - Digitalis purpurea yields cardiac glycosides (digoxin, digitoxin).
  - Eucalyptus oil essential for cough syrups.
  - Tobacco leaves contain nicotine.
  - Atropa belladonna provides atropine.
- Flowers:
  - Poppy (Papaver somniferum) produces morphine (opioid).
  - Vinca rosea produces vincristine and vinblastine (anti-neoplastic).
  - Rose petals are used for rose water tonic.
- Fruits:
  - Senna pod contains anthracine, used as a purgative.
  - Calabar beans yield physostigmine, which acts as a cholinomimetic.
- Seeds:
  - Nux vomica seeds produce strychnine, a CNS stimulant.
  - Castor oil seeds provide castor oil.
- Roots:
  - Ipecacuanha induces vomiting and is amoebicidal.
  - Rauwolfia serpentina yields reserpine, a hypotensive agent.
- Bark:
  - Cinchona bark delivers quinine and quinidine (antimalarial and antiarrhythmic).
  - Anticholinergic agents from Atropa belladonna and Hyoscyamus niger.
Forms of plant drugs include extracts, infusions, decoctions, and powders; they contain chemicals like alkaloids, glycosides, oils, resins, and tannins.

Antibiotics derived from fungi and bacteria emerged after the discovery of penicillin in 1928.
Common antibiotics: penicillin, streptomycin, tetracycline, chloramphenicol, erythromycin.

Comprises metals, metalloids, non-metal substances, and compounds.
Minerals like iron and zinc serve specific medical purposes, such as treating anemia and enhancing immune functions.

Semi-Synthetic Drugs:
- Retain the nucleus of a natural source while altering its structure.
- Complex and costly.
- Examples include 6-aminopenicillanic acid and semi-synthetic human insulin.
Synthetic Drugs:
- Created in laboratories from organic/inorganic compounds.
- Examples include chloroform, ether, nitrous oxide, and various classes such as antihistamines and anticonvulsants.

Involves gene cloning through DNA cleavage using restriction endonucleases.
New genetic combinations are inserted into bacterial cultures to produce drugs.
Products include human insulin, growth hormones, vaccines, and granulocyte-colony stimulating factors.

Advantages:
- Significant quantities of drugs can be produced.
- Purity of drugs obtained is high.
- Less antigenic response in subjects.
Disadvantages:
- Requires well-equipped laboratories.
- Needs highly trained personnel.
- Technique is complex and intricate.