Introduction
Crude drugs are natural substances obtained from plants, animals or minerals in their raw form. They are used directly or after simple processing like drying or size reduction, without changing their chemical composition. Depending on their structure, crude drugs are divided into organized and unorganized types. Organized drugs come from cellular plant parts such as leaves, roots or bark. Unorganized drugs are plant exudates or animal products that lack cellular structure, such as latex, gums, mucilage, honey and wax.
Need for Classification
A proper classification system helps in studying, identifying, comparing and understanding crude drugs. Since thousands of medicinal plants are used in systems like Ayurveda, Siddha and Unani, a simple and systematic arrangement is essential. An ideal classification should be easy to use, logical and free from confusion.
Major Classification Systems of Crude Drugs
Crude drugs are commonly classified using the following seven methods:
- Alphabetical classification
- Morphological classification
- Taxonomical classification
- Pharmacological classification
- Chemical classification
- Chemo-taxonomical classification
- Sero-taxonomical classification
1. Alphabetical Classification
In this system, drugs are arranged alphabetically by their English or Latin names. This method is followed in major pharmacopeias like the Indian Pharmacopoeia, British Pharmacopoeia and United States Pharmacopoeia.
Examples
Acacia, Benzoin, Cinchona, Fennel, Gentian, Jalap, Liquorice, Opium, Senna, Wool fat.
Advantages
- Simple and quick reference.
- Easy to locate or add new entries.
Disadvantage
- No scientific relationship between successive drugs.
2. Morphological Classification
This method arranges drugs based on their external appearance or the plant part used. Drugs are grouped under leaves, roots, bark, flowers, fruits, seeds, etc.
Organized Drugs
These contain cellular structure. Examples: leaves, barks, stems, fruits, seeds.
Unorganized Drugs
These lack cellular structure. Examples: aloe juice, opium latex, agar, honey, beeswax, essential oils.
Advantages
- Easy to study and identify adulteration.
- Useful even when chemical nature is unknown.
Disadvantages
- Morphology may change on drying or storage.
- Does not show chemical or therapeutic relationship.
3. Taxonomical Classification
This system groups crude drugs based on botanical classification. Plants are arranged into families, genera and species based on their evolutionary relationships and structures like flowers, fruits and leaves.
Advantages
- Gives clear idea about related species and varieties.
- Useful for evolutionary studies.
Disadvantages
- No idea about chemical nature or pharmacological action.
4. Pharmacological Classification
In this system, drugs are grouped based on their therapeutic action, such as antimalarial, cardiotonic, laxative, analgesic, antitussive and others.
Examples
Digitalis, squill and strophanthus are grouped together as cardiotonics.
Advantages
- Clinically relevant and easy for therapeutic learning.
- Helps in selecting substitutes with similar action.
Disadvantages
- Some drugs have more than one action.
- No relation to botanical source or chemical nature.
5. Chemical Classification
Here drugs are grouped according to their major chemical constituents. This method is widely used in phytochemistry and research.
Examples
- Carbohydrates: Acacia, Tragacanth, starch, agar.
- Glycosides: Senna, Digitalis, Aloe.
- Tannins: Amla, Catechu.
- Volatile Oils: Cinnamon, Fennel, Mint, Clove.
- Alkaloids: Cinchona, Belladonna, Opium, Rauwolfia.
- Lipids: Castor oil, Almond oil, beeswax.
- Resins: Cannabis, Turmeric, Myrrh, Ginger.
Advantages
- Helpful for understanding therapeutic action.
- Useful for chemical and pharmacological studies.
Disadvantages
- Many drugs contain multiple chemical groups.
- Does not show source or plant morphology.
6. Chemo-Taxonomical Classification
This system combines chemistry with taxonomy. Plants producing similar chemical constituents are grouped together. It helps in understanding biosynthesis and evolutionary trends.
Examples
- Tropane alkaloids in Solanaceae family.
- Berberine in Berberis species.
- Rutin in Rutaceae members.
Advantages
- Shows relationship between chemical constituents and plant evolution.
- Useful in identifying new drug sources.
Disadvantages
- Does not indicate therapeutic activity.
- Does not distinguish organized/unorganized drugs.
7. Sero-Taxonomical Classification
This method uses antigen–antibody reactions for classifying plants. Proteins and enzymes act as antigens and help determine relationships between plant groups.
Advantages
- Helps trace evolutionary relationships using molecular information.
- Reduces errors related to environmental variations.
Disadvantages
- Difficult to trace ancient evolutionary changes.
- Hard to interpret intermediate stages between characters.
Detailed Notes:
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