The scope and practice of pharmacognosy

The scope and practice of pharmacognosy

Until relatively recently pharmacognosy was regarded, almost exclusively, as a subject in the pharmaceutical curriculum focused on those natural products employed in the allopathic system of medicine. Coincident with the increasing attractiveness of alternative (complementary) therapies and the tremendous range of herbal products now generally available to the public, regulatory requirements covering medicinal herbs are being introduced by many countries in order to control the quality ofthese products. Monographs are now available on a large number of such drugs giving descriptions, tests for identity and purity and assays of active constituents. These monographs are being compiled by a number of bodies (see below). In this respect recognition should be given to the pioneering production ofthe Brirlsh Herbal Pharmacopoeia, first produced in 1974 with subsequent editions, and a new one pending. Pharmacognosy is also important in those countries having their own systems of medicine in which plants are important components.

Although pharmacognosy is principally concerned with plant materials, there are a small number of animal products which are traditionally encompassed within the subject; these include such items as beeswax, gelatin, woolfat, vitamins, etc. Other natural products such as the antibiotics, hormones and others may or may not be involved, depending on the teaching practice of a particular institution. As is shown in Chapter 16 marine organisms, many of the animal kingdom, are receiving increasing attention. Materials having no pharmacological action which are of interest to pharmacognosists are natural fibres, flavouring and suspending agents, colourants, disintegrants, stabilizers and filtering and support media. Other areas that have natural associations with the subject are poisonous and hallucinogenic plants, allergens, herbicides, insecticides and yrolluscicides.

Vegetable drugs can be arrangetl for study under the following headings.

1 . Alphabetical. 

Either Latin or vernacular names may be used. This arrangement is employed fol dictionaries, pharmacopoeias, etc. Although suitable for quick reference it gives no indication ofinterrelationships between drugs.

2. Taxonomic. 

On the basis of an accepted system ofbotanical classification (Chapter 3), the drugs are arranged according to the plants from which they are obtained, in classes, orders, families, genera and species. It allows for a precise and ordered arrangement and accommodates any drug without ambiguity. As the basic botanical knowledge of pharmacy studentsd decreases over the years this system is becoming less popular for teaching purposes.

3. Morphological. 

The drugs are divided into groups such as the following: leaves, flowers, fruits, seeds, herbs and entire organisms, woods, barks, rhizomes and roots (known as organized drugs), and dried latices, extracts, gums, resins, oils, fats and waxes (unorganized drugs). These groupings have some advantages for the practical study of crude drugs; the identification of powdered drugs (see Chapter 44) is often based on micro-morphological characters.

4. Pharmacological or Therapeutic. 

This classification involves the grouping of drugs according to the pharmacological action of their most important constituent or their therapeutic use. R. Pratt and H. W. Youngken Jr. were, in 1956, the first to use this approach for an English language textbook and now, with so many plant materials being screened for specific pharmacological activity, this type of listing is found increasingly in the literature. Its use is illustrated in Chapters 28-32.However, it is important to appreciate that the constituents of any one drug may fall into different pharmacological groups.

5. Chemical or Biogenetic. 

The important constituents, e.g. alkaloids, glycosides, volatile oils, etc., or their biosynthetic pathways, form Until relatively recently pharmacognosyw as regarded, a lmost exclusively, as a subject  in the pharmaceutical cumrriculum focused on those natural products employed in the allopathic system of medicine. Coincident with the increasing attractiveness of alternative (complementary) therapies and the tremendous range of herbal products now generally available to the public, regulatory requirements covering medicinal herbs are being introduced by many countries in order to control the quality of these products. Monographs are now available on a large nurnber of such drugs giving descriptions, tests for identity and purity and assays of active constituents. These monographs are being compiled by a number of bodies (see below). In this respect recognition should be given to the pioneering production of the British Herbal Pharmacopoeia first producedin 1974 with subsequent editions and a new one pending. Pharmacognosy is also important in those countries having their own systems of medicine in which plants are important components.

Although pharmacognosy is principally concerned with plant materials, there are a small number of animal products which are traditionally encompassed within the subject; these include such items as beeswax, gelatin, woolfat, vitamins, etc. Other natural products such as the antibiotics, hormones and others may or may not be involved, depending on the teaching practice of a particular institution. As is shown in Chapter l6 marine organisms, many of the animal kingdom, are receiving increasing attention. Materials having no pharmacological action which are of interest to pharmacognosist are natural filbres, flavouring and suspending agents colourants, disintegrants, stabilizers and filtering and support media. Other areas that have natural association with the subject are poisonous and haliucinogenic plants, allergens, herbicides, insecticides and molluscicides.

Vegetable drugs can be arranged for study under the following headings.

l . Alphabetical. Either Latin or vernacular names may be used. This arrangement is employed for dictionaries, pharmacopoeiase, etc. Although suitable for quick reference it gives no indication of interrelationships between drugs.

2. Taronomic. On the basis of an accepted system of botanical classification (Chapter 3), the drugs are arranged according to the plants from which they are obtained, in classes, orders, families, genera and species. It allows for a precise and ordered arrangement and accommodates any drug without ambiguity. As the basic botanical knowledge of pharmacy students decrease over the years this system is becoming less popuiar for teaching purposes.

3. Morphological. The drugs are divided into groups such as the following: leaves, flowers, fruits, seeds, herbs and entire organisms, woods, barks, rhizomes and roots (known as organized drugs). And dried latices, extracts, gums, resins, oi1s, fats and waxes (unorganized drugs). These groupings have some advantages for the practical study of crude drugs; the identitlcation of powdered dugs (see Chapterz 44) is often based on micro-morphological characters.

4. Pharmacoktgical or Therapeutic. This classification involves the grouping of drugs according to the pharmacological action of their most impoftant constituent or their therapeutic use. R. Pratt and H. W Youngken Jr. were, in 1956. the first to use this approach for an English language textbook and now. with so many plant materials being screened for specitic pharmacological activity this type of listing is found increasingly in the literature. Its use is illustrateid in Chapters 28-32. However, it is important to appreciate that the constituents of any one drug may fall into different pharmacological groups.

5. Chemical or Biogenetic. The important constituents e.g. alkaloids, glycosides, volatile oils, etc., or their biosynthetic pathways. form the basis of classification of the drugs. This is a popular approach when the teaching of phrarmacognosy is phytochernically biased. Anbiguities alise when particular drugs possess a number of active principles belonging to diffrerent phytochemical groups as illustrated by liquorice, ginseng, valeriant etc. The schemeis employed in Chapters 20-27 for aranging the established pharmacopoeia drugs.