Classification of Crude Drugs in Pharmacognosy

Crude drugs are natural substances used as drugs directly or indirectly in their unmodified and unchanged chemical composition. They are obtained from plants, animals, microbes, marine organisms, or minerals. Classification of crude drugs is based on various parameters.

Types of Crude Drugs

Crude drugs are collected by drying these natural sources and later slicing them to extract the drugs. There are two types of crude drugs- organized and unorganized.

Organized Crude Drugs

Crude drugs that contain cellular parts of the source they are collected from are called organized drugs. Herbal teas, extracts, and tinctures often made from plant parts or other sources usually have their anatomical or cellular parts intact. They are called organized drugs. Sometimes, the entire plant is also considered an organized drug.

Unorganized Crude Drugs

Crude drugs that do not have cellular features of a morphological or anatomical nature are categorized under unorganized drugs. They are collected from plants, animals, or minerals, yet they do not contain cellular remnants. Plant exudates, dried extracts, essential oils, waxes, other oils, fats, etc come under this category. Unorganized crude drugs can be in any physical form.

Classification of Crude Drugs

Crude drugs have various natural sources. The organized crude drugs are organic while the unorganized crude drugs could be organic or inorganic minerals.

Due to such a wider variety of sources, a system to classify and study these crude drugs is essential. The chosen method should be simple, and easy to use without ambiguity or confusion. Therefore, for ease of study, crude drugs are classified based on various parameters.

Alphabetical classification
Taxonomical classification
Morphological Classification
Pharmacological classification
Chemical classification
Chemotaxonomical classification
Serotaxonomical classification

Alphabetical Classification

Alphabetical classification is the simplest way to classify crude drugs, where they are arranged alphabetically, according to their English and Latin names. Sometimes, vernacular names are also used. Some books that classify crude drugs are,

Indian Pharmacopoeia
British Pharmacopoeia
British Herbal Pharmacopoeia
United States Pharmacopoeia & National Formulary
British Pharmaceutical Codex
European Pharmacopeia

Advantages
- It is simple to locate or trace a drug and also easy to add one.
- No technical expertise is required to identify drugs.
Disadvantages
- Does not help identify if the drug is organized or unorganized.
- Distinguishing the source of drugs is also possible with this classification.

Taxonomical Classification

Every plant has a different kind of physiological, morphological, anatomical, and serological characteristics. So the taxonomical classification of crude drugs categorizes them as per their kingdom, subkingdom, division, class, order, family, genus, species, etc. There could also be further classification as shown here.

Class
Subclass
Superorder
Order
Family
Subfamily
Tribe
Subtribe
Genus
Species
Variety
Form
Cultivar

Advantages: Classification is easy without having to identify different parameters.
Disadvantages:
- Failed to recognize organized and unorganized drugs.
- Chemical nature and therapeutic effects cannot be identified.

Morphological Classification

This is the classification of crude drugs according to their morphological characters such as leaves, stems, roots, etc.

The drugs collected from these parts come under organized drugs as they have cellular tissues. However, when the plant parts are passed through various extraction processes and when they lose their cellular organization, they will be considered as unorganized drugs.

A few examples of such drugs are Aloe vera, honey, agar, beeswax, gelatin, etc.

ORGANIZED DRUGS	UNORGANIZED DRUGS
Wood	Dried latex
Flowers	Dried juice
Barks	Dried extracts
Flowering parts	Wax
Fruits	Gum
Seeds	Resin
Roots	Volatile oil
Rhizomes	Oil
Herbs	Fats
Hair	Animal products
Fibers	Fossils and minerals

Advantages
- Convenient for practical study when its chemical nature is unidentified.
- Can easily identify adulterants.
Disadvantages
- Biological sources and chemical nature cannot be identified by this method.
- The presence of different chemicals in each part makes it difficult to classify them.

Pharmacological Classification

Pharmacological classification categorizes crude drugs as per their pharmacological action, specifically their active constituents. Since the drugs are categorized according to their therapeutic uses, this classification is also known as therapeutic classification. Some of the categories include drugs that act on systems such as the central nervous system, cardiovascular system, respiratory system, etc.

Advantages
- Pharmacological classification is quick and easy, without any repetitions.
- Drugs can be categorized as per their therapeutic usage and chemical constitution.
Disadvantages
- Does not specify whether the drugs come under the organized or unorganized category.
- Entries are unrelated when compared to the previous ones.

Chemical Classification

Chemical classification of crude drugs is based on their active constituent such as alkaloids, tannins, resins, saponins, etc. Here, the drugs are grouped on their chemical nature, regardless of their morphological or taxonomical characters.

Advantages: Can easily identify the chemical constituents and medicinal uses.
Disadvantages: It is difficult to place the drugs due to different chemical constituents in different plants.

Chemotaxonomical Classification

Chemotaxonomical classification is based on certain chemical constituents in plants of different classes or other taxonomical parameters, that link them in a relationship. For eg., tropane alkaloids are seen in members of Solanaceae, rutin in Rutaceae, etc.

Advantages:
- Helps with product research in specific groups of plants.
- Solves many issues of taxonomical classification.
- Provide quality assessment of the drugs.

Disadvantages:
- The presence of different chemical content in different plant parts makes it difficult to classify the plant.
- The content and distribution of the chemical constituents may vary according to different factors.

Serotaxonomical Classification

Serotaxonomical classification of crude drugs is based on their serology, the study of antigen-antibody interaction. Since these are proteins that carry taxonomical information, they are used as antigens in serotaxonomy.

This helps compare the non-morphological characteristics from the taxonomical data. A single protein is chosen for study and is compared with the same from different plants. The resultant data will have similarities and differences between these plants. In taxonomy, this data will help differentiate the genus, family, subfamily, etc.

References

https://www.gputtawar.edu.in/downloads/classificationofcrudedrugs.pdf
https://www.mespharmacy.org/wp-content/uploads/2020/07/Classification-of-crude-Drugs.pdf
Shah, Biren N, Avinash Seth. (2010). Textbook of Pharmacognosy and Phytochemistry. Elsevier.