Natural Sources of drugs in pharmacology
There are various sources of drugs available in nature such as plants, animal and minerals. in this article we will discuss about Natural and microbial source of drugs.
Plant sources of drugs
Many drugs available from plants are even today used in the treatment of pathological conditions. With the increasing tendency for the use of alternate medicine, this source has gained more importance in the recent past. The pharmacological activities of plants are attributed to certain active principles in plants. They are alkaloids, glycosides, fats, oils, tannins, saponins etc.
Alkaloids
Alkaloids are nitrogenous substances obtained from various parts of the plant. Alkaloids containing oxygen are solids and comparatively non volatile (cocaine) while those that do not contain oxygen are liquids and volatile (nicotine, lobeline and coniine). these are insoluble in water while their salts (atropine sulphate, caffeine citrate) are soluble in water.
Alkaloids are bitter to taste. They are incompatible with the alkalies, tannic acid and heavy metals. and Alkaloids represent the waste products of plant metabolism and their names end with ‘ine’.
Alkaloids should be administered in small quantities and when given in excess they may produce death without much postmortem changes for diagnosis. (Adrenaline is considered as animal alkaloid).
Glycosides
Glycosides are non-nitrogenous substances obtained from plants. On hydrolysis yield two molecules namely a sugar molecule and a ‘genine’ or ‘aglycone’ molecule. Sugar helps in the dissolution of the preparation while the pharmacological action rests with the ‘aglycone’. When the sugar molecule is glucose, the glycoside is known as glucoside.
Cardiac glycosides digitalis, strophanthus and squill play a major role in the treatment of congestive cardiac failure. Cyanogenetic glycoside is one in which hydrocyanic acid is released on glycolysis.
Oils
There are two types of oils namely fixed oils and volatile oils. Volatile oils are also known as essential oils. Castor oil, coconut oil etc. are fixed oils while turpentine oil, eucalyptus oil etc. are volatile oils.
Fixed oils are obtained by expression while volatile oils are obtained by distillation. (Mineral oils are obtained from the earth and some ae used pharmacologically. Eg: Liquid paraffin.)
Tannins
Tannins are non-nitrogenous phenol derivatives found especially in leaves and bark. They are astringent in nature and form inky solutions with ferric salts. Catechu a tannic acid is used in the control of diarrhoea.
Examples of tannins: Black catechu, Pale catechu
Saponins
Saponins are non-nitrogenous substances resembling glycosides. They are soluble in water and on shaking they give persistent foam. When the saponin is toxic it is known as sapotoxin. On hydrolysis saponins split into sugar and aglycone (sapogenin).
Example of Saponins: Fenugreek, Ginseng
Resins
Resins are solid brittle substances formed from terpenes by oxidation. They are insoluble in water. Resin can be oleo resin, gum resin or balsams.
Examples of Resins: Asafoetida, Camphor, Storax
Gums
Gums are dried exudates obtained by incision on stems of various plants. They form a jelly with water.
Example of gums: Gum acacia
Mineral source of drugs
Metallic and nonmetallic minerals provide various inorganic materials not available from plants or animals. Mineral sources are used as they occur in nature or can be combined with other ingredients.
The drugs that are included in this category include metals and their salts, non metals, metalloids, acids, alcohols and coaltar drugs etc.
Examples of Mineral source of drugs: sodium chloride, copper sulphate, magnesium sulphate, potassium permanganate, etc.
Minerals are used in the purified form as drugs.
Animal source of drugs
- The body fluids or glands of animals are also natural drug sources. The drugs obtained from animal sources include-
- hormones, such as insulin
- oils and fats (usually fixed), such as cod-liver oil
- enzymes, which are produced by living cells and act as catalysts, such as pancreatin and pepsin
- vaccines, which include suspensions of killed, modified, or attenuated microorganisms, or antigenic materials obtained from these.
Synthetic sources of drugs
A number of drugs synthesized in the laboratory are used most commonly. Even natural products such as hormones, antimicrobials etc. are also synthesized in the laboratory.
Microbial source of drugs
Microbes provide an important source of drugs especially the antibiotics. All the antibiotics used against a variety of pathogens and also cancer are obtained from fungi, bacteria or actinomycetes. Some systemic drugs like ergot alkaloids (fungal source) are also obtained from microbes.
Example of microbial drugs: Penicillin from Penicillium notatum, Streptomycin, Tetracyclines, Chloramphenicol from Streptomyces species.