Sources of drugs are of various types and these drugs can be obtained from various sources such as:
1. Animal, e.g. antitoxic sera, gonadotrophines, heparin, insulin and thyroid extract.
2. Drugs produced by genetic engineering (i.e. by DNA recombinant technology), e.g. human growth hormone and human insulin.
3. Mineral, e.g. zinc, aluminum hydroxide, liquid paraffin, lithium, magnesium trisilicate can also be good Sources of drugs.
4. Micro-organisms: Important sources of antibacterial substances (e.g. penicillin and other antibiotics) are fungi and bacteria which are isolated from soil.
5. Synthetic Sources of drugs: In clinical practice, majority of the drugs used are synthetic such as diazepam, paracetamol, clonidine, corticosteroids, etc.
6. Plant: For example atropine, emetine, quinine, morphine, digoxin and reserpine. There are a number of pharmacologically active principles in plants such as:
i. Oils: They are of following types:
a. Fixed oils: Chemically, the fixed oils are glycosides of palmitic, oleic and stearic acids. They are fats. Castor oil is pharmacologically active and is used as a laxative.
b. Volatile oils are volatile, essential or flavoring oils. Chemically, they consist of hydrocarbon terpene or some polymer of it. They are not fats. They are useful Sources of drugs as:
• Antiseptic, e.g. used in mouth- washes and pastes.
• Carminative, e.g. ginger and oil of eucalyptus.
• Flavouring agents, e.g. oil of peppermint.
• Counter irritants, e.g. turpentine oil.
• Analgesic, e.g. oil of clove in toothache.
c. Mineral oil, e.g. liquid paraffin. It is a hydrocarbon. It is derived from petroleum and is used as a lubricant laxative. It is devoid of food value and is one of the common Sources of drugs.
ii. Alkaloids: Alkaloids contain cyclic nitrogen. They are insoluble in water. They are basic substances. So they combine with acids to form well-defined water soluble salts, e.g., atropine, emetine and morphine.
iii. Glycosides are Sources of drugs: Chemically, these are ether like combination of sugars with other organic structures. They are hydrolyzed to a sugar and non-sugar moiety (aglycon or genin) on heating with mineral acid, e.g. digoxin hydrolyses into digitoxose and digoxigenin. When a glycoside produces glucose on acid hydrolysis, it is called a glucoside, e.g. strophanthin.
iv. Gums: These are secretory products of plants, e.g. agar, gum acacia and gum tragacanth. Agar is employed as a bulk laxative while the other two are used in pharmacy as suspending and emulsifying agents.
v. Resins: They are formed in plants by oxidation or polymerization of volatile oils. They are insoluble in water but soluble in alcohol.
vi. Oleoresins are mixtures of volatile oil and resins, e.g. male fern extract.
vii. Tannins are also common Sources of drugs: These are non-nitrogenous constituents of plants. They have astringent action upon mucous membrane and thus exert a protective action. For example, tincture catechu releases tannic acid in the small intestine and soit is used in the treatment of diarrhea.
7. Antibacterial substances also form the Sources of drugs: These are derived from fungi and moulds, e.g. penicillin, kanamycin, tobramycin.
[Source: Principles of Pharmacology for Dental Studies]