Source and Composition of Drugs

Sources and composition of drugs


Most drugs currently used in veterinary practice are synthesized by the organic chemist, screened and tested by the pharmacologist &toxicologist, prepared in suitable dosage form by the pharmaceutical chemist, evaluated by the clinical investigator, and marketed by pharmaceutical company.

Classification of drugs:

1. Drugs classification basing on source (source of drugs).
A. Natural Sources: I. Vegetable/ plant drugs.
II. Animal drugs. .
III. Microbial drugs.
IV. Mineral drugs.
B. Synthetic & semi synthetic drugs.
Vegetable Drugs

Plate kingdom offers a variety of pharmacologically active principles. The ancient Hindu literature and the oldest system of medicine “Ayurveda” recognized the medicinal value of several plant preparations. Important drugs like Digitalis, reserpine, morphine, quinine, atropine, curare, etc., all were originally obtained from plants. Even today, plants continue to remain as one of the major source of drugs. The medicinal value resides in all parts of plant;, however, the concentration of the active principle varies in different parts—seeds, flowers, leaves, bark, roots, rhizomes and bulbs forms important sources of several drugs. Active principles obtained from plants are,

(1) Alkaloids: Basic nitrogenous substances, which are insoluble in water, but form, water soluble salts with acids. Higher concentrations found in seeds & roots, Alkaline in reaction, intensely bitter to taste. Potent poisons leaving no post mortem changes. Salts of heavy metals, Iodine, and tannic acid precipitate these. Name of the alkaloid ends with “ine”, like, Morphine, Atropine, Emetine, Nicotine, strychnine, and reserpine.

(2) Glycosides: are various sugars combined with organic structures through an ether- like linkage. Sugar part is called Glycon and the enzyme hydolysis these two will breakout. Pharmacological action resides in a glycon and the sugar influences the solubility and permeability of the glycosides. These compounds are neutral and will not form salts, soluble in alcohol but not in water. Eg. Digoxin, Ouabain, Linamarin. Amygdalin. Words end with letters “in”.
Some glycosides following enzyme hydrolysis produce HCN—called Cyanogentic glycocides. Jawar, Yougst. Cardiac glycosides: specific action on heart. Digitalis.

(3) Saponins: Non-nitrogenous substances soluble in water and capable of causing foam/ froth when shaken with water. Upon hydrolysis they split into a sugar part and a non-sugar part (sapogenin) quilla senega like glycosides, hence considered as a sub – class of glycosides. Used as emulsifiers (quillaria).

(4) Tannins: are non-nitrogenous substances having a characteristic astringent action upon the mucosa by precipitating the proteins (Astringent action). Tannins are soluble in water Eg. Catechu, Kino, Galls.

(5) Resins: Brittle, amorphous compounds formed from the oxidation or polymerization of terpenes, components of volatile oils. They are insoluble in water, but soluble in organic solvents.Eg., Podophyllum resin, jalap.

(6) Oleoresins: Mixtures of volatile oils and resins. Eg. Terpentine oil, male fern extract.

(7) Neutral Principles: Active principles of plants not conforming to any of above composition not known, bitter in taste. Aloin , santonin.

(8) Oils: Two types (i) Fixed oils (ii) volatile oils
(i) Fixed oils: Are gycerides of oleic, palmitic and stearic acids. These have food values. Stable will not evaporate when exposed to air. Eg. Castor oil, linseed oil, peanut oil.
(ii) Volatile oil: They will evaporate readily and have a characteristic odor. Are also called as aromatic essential, ethereal or flavoring oils. These are used for different purposes.
Carminative: eucalyptus oil, turpentine oil.
Antiseptics: peppermint oil
Counter irritants: turpentine oil,
Analgesics: oil of wintergreen, oil of clove.
Flavoring agent: peppermint oil


Fixed oils
Volatile oils
1. Extracted or expressed from fruits/ seeds
1.Distilled by steam distillation, plants, leaves, flowers are used.

2. Liquids at room temp., solidify on cooling.
2.remain liquid even on cooling. Some are solid on room temp. Camphor, menthol

3. Insoluble in water, soluble in alcohol. Chloroform, ether.

3. Slightly soluble in water, miscible in fixed oils, soluble in alcohol, chloroform.
4. Form soap with alkalis and metallic oxides.

4. No soaps
5. Decompose and becomes rancid on heating

5.no tendency to become rancid
6. Lubricant properties
6. Not
7. Leave a grease spot on paper
7. Not
8. Acts as nutrients & emollientliquid esters of higher fatty acids (oleic, palimitic & stearic and glycerin.

8. No nutrient or emollient properties. Composition of volatile oils consists mostly of liquid hydro- carbon called terpens or pinins.



9. Gums: Polysaccharides secreted by certain trees and capable of forming thick mucilaginous colloids when mixed with water. These are pharmacologically inert and used as suspending or emulsifying agents and stabilize mixtures of other active drugs in liquid dosage forms. Eg. gum acacia, gum arabic, gum tragacanth.

10. Oleo gum resins: mixture of gum, resin & volatile oil. Obtained as exudates from plants asafetida, myrrh.

11.Balsams: Resins containing Benzoic or cinnamon acid. They have agreeable odor. Balsam of Tolu: skin dressings, Balsam of Peru: used in cough.

Animal Drugs

Liver, endocrine glands and secretary organ of animals are used to extract active constituents.

i. Hormones: Posterior pituitary extract Insulin, Thyroxin, Gonadotrophins.
ii. Vitamins: Cod or shark liver oils as rich source of vitamin A&D.
iii. Ontisera: Canine distemper, antisera, antisnake venom.
iv. Others: Heparin, Liver extract.

Microbial Drugs

Bacteria and fungi isolated from soil are the important sources of antibiotics. Eg. Penicillin, streptomycin, gentamicin, neomycin. The viruses and bacteria causing infectious diseases are also valuable in the preparation of vaccines. Dried yeast is an important source of B- complex vitamins.

Mineral Drugs

Many inorganic compounds are used in the treatment of a variety of disease states. Mag. Oxide-Antacid, Mag.Sul- purgative, pot.iodide- expectorant, pot.nitrate- diuretic, Fe.Sulfate- heamatonic.

Synthetic Drugs

Majority of drugs in the present day usage are of synthetic origin. The drugs, which are exclusively included under this source, are anaesthetizes, antiprotozoan drugs, antiseptics, tranquilizers, antiarrhythmies, antiarrhythmies.

With advancement of medical chemistry and the knowledge of structure activity relationship, several drugs of natural origin are chemically altered to produce new compounds with specific pharmacological actions. Such new drugs are called semi- synthetic drugs. Eg. Morphine derivatives, antagonists, Dihydrostreptomycin, semi synthetic penicillins.


Classification of drugs basing on chemical nature (composition of drugs)


A. Inorganic Drugs: a. Acids: Benzoic acid, acetic acid, salicylic acid.
b. Bases: sod. bi.Carb., Mag.hydroxide
c. Salts: NaCl, Mgo, Fe.Sulfate, CuSo4, CoCl.
d. Metals: Cu, Iron, and Zinc.
e. Metalloids: Arsenic, Antimony, and Phosphorus.
f. Non metals: - Halogens& Sulphar, water and oxygen.

B. Organic Drugs: a. Alkaloids: Morphine, atropine, nicotine.
b. Glycosides: digitoxin, gitoxin, amgdalin.
c. Saponin: quillaria.
d. Tanins: catechu,
e. Resin: podophyllum
f. Oleoresins: turpentine oil
and, Gums, Oils, Enzymes and Hormones

Whole herb – chirrata
Root -- gention, asafoetida, aconite
Bark--- cinchona
Stem or modification---- Rhizome – Rubarb, Ginger
Squill -- bulb

Gums & Resins
Leaves—Belladona, Digitalies.
Flowers – Santonin, canmodies indica,
Seeds -- Nurvomica, castor oil.
Fruits-- Citrus, Capsicum, PIPPER.