Nature and Sources of Drugs

PHARMACOLOGY - INTRO - Nature & Source of DRUGS

1. Nature and Sources of Drugs PHARMACOLOGY

2. Synthetic Source Vegetable Source Animal Source Microbiological Source Mineral Source Genetically Engineered / Biotechnology – Based Drugs / Biopharmaceuticals / Biological Agents The drugs can be obtained from either of the following sources

3. Presently, the majority of drugs are obtained synthetically or semi-synthetically. Some of the drugs which were earlier obtained from plant or animal source are today synthesized in the laboratories, the advantages being: 1. Their quality can be better controlled. 2. The process is easier and cheaper. 3. The chemical structure of the prototype be modified in search of better, more potent and safer drug because the pharmacological activity of a drug is a function of its chemical structure and physical properties. Such examples : Aspirin, paracetamol, phenytoin, chlorpromazine, amphetamine, chloroquine and various sulfa drugs belong to this class of drugs 1. SYNTHETIC SOURCE :

4. 2. VEGETABLE SOURCE : Drugs belonging to the following categories are usually obtained from vegetable source. Alkaloids Glycosides Oils Gums Tannins Resins

5. Alkaloids These are nitrogenous heterocyclic bases derived from plants. Alkaloids as such are insoluble in water but being alkali-like, they form salts with acids which are water soluble. Alkaloids are pharmacologically active principle of plants. Examples: atropine from Atropa belladona , quinine from Cinchona bark, morphine from Papaverum somniferum  (poppy), reserpine from Rauwolfia serpentina and nicotine from tobacco leaves. The names of all alkaloids usually end with 'ne".

6. Glycosides are those plant products, where a sugar moiety is joined to a non-sugar moiety with a ether linkage (-O-). However, if the sugar moiety is glucose, the glycoside is called a glucoside and if it is an amino-sugar then it is called aminoglycoside. Glycosides

7. On hydrolysis with mineral acids, all glycosides split up into the sugar and the non-sugar residues. The pharmacological activity of a glycoside resides in its non-sugar molecule which is called an 'aglycon" (or genin ). The sugar portion, however, governs the pharmacokinetic characteristics of the glycoside. Some important examples of glycosides are cardiac glycosides used in the treatment of CHF, e.g., digitoxin, digoxin which are obtained from foxglove leaves (Digitalis purpurea) and ouabain obtained from Stropanthus gratus . Aminoglycosides are, rather, obtained from microorganisms (and not from plants source) and are used as antimicrobial agents.

8. Oils These are obtained from leaves or flower petals by steam distillation. These are steam volatile, have aroma, have no caloric or food value, do not form soaps with alkalis and do not become rancid (foul smell) on prolonged stay. These are mainly used as carminatives, astringents in mouth washes, or as flavouring agents, e.g. , eucalyptus oil, clove oil, peppermint oil and ginger oil. Some of them may be solid at room temperature and sublimate on heating. e.g .. menthol and camphor. Essential Oils (or volatile oils)

9. These are non-volatile, have caloric or food value, form soaps with alkalis and become rancid after prolonged stay. These are obtained by solvent extraction of crushed seeds. Examples are groundnut oil, coconut oil and olive oil. Fixed oils have little pharmacological use except for castor oil (purgative) or arachis oil (demulcent). Fixed Oils

10. Gums These are the colloidal exudates of the plants. They either swell, or dissolve or form adhesive mucilage in water. These are used as emulsifying or suspending agents, e.g ., gum acacia and gum tragacanth. Tannins These are non-nitrogenous phenolic derivatives from plant source and are soluble in water. They are mainly used as astringents, e.g. , tinct. catechu and tinct. rhubarb.

11. Resins These are polymers of volatile oil and are insoluble in water, e.g., benzoin (used as inhalation in common cold), tinct, benzoin (as antiseptic protective sealing over bruises), colophony (which is an oleoresin used as an ingredient in various plasters) and shellac (from Lucifer lacca , used for enteric coating of tablets). Balsams are also a type of resin (a mixture of resin, benzoic acid and volatile oil), e.g.. Tolu balsam which is used as an expectorant in cough mixtures.

12. 3. ANIMAL SOURCE : Many drugs are obtained from animal source and these comprise hormones, vitamins, vaccines and sera, eg , insulin from pancreas, vitamin B, from liver extract and thyroxine from thyroid; it also includes cholera, BCG, TAB, smallpox, polio and antirabies vaccines, antidiphtheria and antitetanus sera.

13. 4. MICROBIOLOGICAL SOURCE : Some of the fungi, moulds and bacteria are important sources of many life-saving drugs, e.g., penicillin from - Penicillium notatum, chloramphenicol from Streptomyces venezuelae , griseofulvin (an antifungal drug) from Penicillium griseofulvum and - aminoglycoside group of antibiotics, like streptomycin from Streptomyces griseus and neomycin from Streptomyces  frudiae .

14. 5. MINERAL SOURCE : Many pharmacotherapeutic agents are obtained from the mineral source. These agents are solid or liquid and mineral preparations. Solid/Powder and Liquid Preparations The solid and powder preparations dispensed for medical use are: ferrous sulphate (in anaemia), magnesium sulphate (as purgative), aluminium hydroxide, calcium carbonate, sodium bicarbonate (as antacids) and kaolin (aluminium silicate) as adsorbent in antidiarrhoeal preparations. Tincture iodine and povidone iodine solutions used as antisepties are some examples of liquid mineral preparations. Radioactive isotopes are a relatively newer source of mineral drugs, eg , for the diagnosis and treatment of thyrotoxicosis and thyroid malignancy. ii) Mineral Preparations These are mostly petroleum products and are obtained by dry distillation of wood. These have no food value and do not become rancid. These are mainly used as vehicles for preparation of ointments, e.g., hard and soft paraffin and also as purgative-laxative, e.g.. liquid paraffin.

15. 6. GENETICALLY ENGINEERED / BIOTECHNOLOGY-BASED DRUGS / BIOPHARMACEUTICALS / BIOLOGICAL AGENTS: Biotechnology-based drugs are prepared by genetic engineering which means the manipulation of genetic material using recombinant DNA technology. In this method a desired gene is inserted into a very fast multiplying non-pathogenic strain of some bacteria, e.g., E. coli-K12. This host cell will now produce large amounts of the gene-directed proteins which are required. E. coli, otherwise, does not synthesise these proteins. Examples: Humulin (hu- man insulin by inserting proinsulin gene); Recombinax -HB (a hepatitis B vaccine) and Human erythropoietin (a hormone that stimulates the production of RBC).

16. T H A N K Y O U