Meaning of Pharmacognosy

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Chapter: Pharmacognosy and Phytochemistry : History, Definition and Scope of Pharmacognosy

Pharmacognosy, known initially as materia medica, may be defined as the study of crude drugs obtained from plants, animals and mineral kingdom and their constituents.


MEANING OF PHARMACOGNOSY

 

Pharmacognosy, known initially as materia medica, may be defined as the study of crude drugs obtained from plants, animals and mineral kingdom and their constituents. There is a historical misinformation about who created the term pharmacognosy. According to some sources, it was C. A. Seydler, a medical student at Halle, Germany, in 1815; he wrote his doctoral thesis titled Analectica Pharmacognostica. However, recent historical research has found an earlier usage of this term. 


The physician J. A. Schmidt (Vienna) used that one in his Lehrbuch der materia medica in 1811, to describe the study of medicinal plants and their properties. The word pharmacog-nosy is derived from two Latin words pharmakon, ‘a drug,’ and gignoso, ‘to acquire knowledge of’. It means ‘knowledge or science of drugs’.

Crude drugs are plants or animals, or their parts which after collec-tion are subjected only to drying or making them into transverse or lon-gitudinal slices or peeling them in some cases. Most of the crude drugs used in medicine are obtained from plants, and only a small number comes from animal and mineral kingdoms. 

Drugs obtained from plants consist of entire plants, whereas senna leaves and pods, nux vomica seeds, ginger rhizome and cinchona bark are parts of plants. Though in a few cases, as in lemon and orange peels and in colchicum corm, drugs are used in fresh condition, and most of the drugs are dried after collections. Crude drugs may also be obtained by simple physical processes like drying or extraction with water. Therefore, aloe is the dried juice of leaves of Aloe species, opium is the dried latex from poppy capsules and black catechu is the dried aqueous extract from the wood of Acacia catechu. Plant exudates such as gums, resins and balsams, volatile oils and fixed oils are also considered as crude drugs.

Further drugs used by physicians and surgeons or phar-macists, directly or indirectly, like cotton, silk, jute and nylon in surgical dressing or kaolin; diatomite used in filtration of turbid liquid or gums; wax, gelatin, agar used as pharmaceutical auxiliaries of flavouring or sweetening agents or drugs used as vehicles or insecticides are used in pharmacognosy.

Drugs obtained from animals are entire animals, as can-tharides; glandular products, like thyroid organ or extracts like liver extracts. Similarly, fish liver oils, musk, bees wax, certain hormones, enzymes and antitoxins are products obtained from animal sources.

Drugs are organized or unorganized. Organized drugs are direct parts of plants and consist of cellular tissues. Unorganized drugs, even though prepared from plants are not the direct parts of plants and are prepared by some intermediary physical processes, such as incision, drying or extraction with water and do not contain cellular tissue. Thus aloe, opium, catechu, gums, resins and other plant exudates are unorganized drugs.

Drugs from mineral sources are kaolin, chalk, diatomite and other bhasmas of Ayurveda.


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