Pharmacognostical Scheme

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

To describe drugs in a systematic manner is known as pharmacognostical scheme, which includes the following headings:



To describe drugs in a systematic manner is known as pharmacognostical scheme, which includes the following headings:


Biological Source


This includes the biological names of plants or animals yielding the drug and family to which it belongs. Botanical name includes genus and species. Often some abbrevia-tions are written after the botanical names, of the biologist responsible for the classification, for example, Acacia arabica Willd. Here Willd indicates the botanist responsible for the classification or nomenclature. According to the biennial theory, the botanical name of any plant or animal is always written in italic form, and the first letter of a genus always appears in a capital later.


Biological source also includes the family and the part of the drug used. For example, biological source of senna is, Senna consists of dried leaflets of Cassia angustifolia Delite, belonging to family Leguminosae.


Geographical Source


It includes the areas of cultivation, collection and route of transport of a drug.


Cultivation, Collection and Preparation


These are important to mention as these are responsible for quality of a drug.


Morphological Characters


In case of organized drugs, the length, breadth, thickness, surface, colour, odour, taste, shape, etc. are covered under the heading morphological characters, whereas organolep-tic properties (colour, odour, taste and surface) should be mentioned, if the drug is unorganized.


Microscopical Characters


This is one of the important aspects of pharmacognosy as it helps in establishing the correct identity of a drug. Under this heading all the detailed microscopical characters of a drug is described.


Chemical Constituents


The most important aspect which determines the intrinsic value of a drug to which it is used is generally described under this heading. It includes the chemical constituents present in the drug. These kinds of drugs are physiologi-cally active.




It includes the pharmaceutical, pharmacological and bio-logical activity of drugs or the diseases in which it is effective.




The drug which is used during non-availability of origi-nal drug is known as substituent. It has the same type of physiological active constituents; however, the percentage quantity of the drug available may be different.




With the knowledge of the diagnostic characters of drugs, the adulterants can be detected. One should have the criti-cal knowledge of substances known to be potential adul-terants. Most of the times the adulterants are completely devoid of physiologically active constituents, which leads in the deterioration of the quality. For example, mixing of buffalo milk with goat milk is substitution, whereas mixing of water in the milk is adulteration. In the first case, goat milk is substitute and in the second case water is adulterant.


Chemical Tests


The knowledge of chemical tests becomes more important in case of unorganized drugs whose morphology is not well defined.


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