Crude Drug and its Classification - Pharmacognosy

Crude Drug and its Classification :- 

Crude drugs are substances obtained from natural resources like plants, animals, and minerals, used for preventing, diagnosing, treating, or relieving symptoms of diseases or abnormal conditions. They are classified as organized (cellular) or unorganized (acellular) based on their cellular structure. Organized drugs are solid, semi-solid, or liquid, while unorganized drugs are organs of plants or animals. They are classified based on physical characteristics such as solubility, density, optical rotation, and refractive index. Crude drugs are classified alphabetically, chemically, morphologically, taxonomically, and pharmacognostically. 

What is Drug ?

A drug is any substance (other than food) that is used to prevent, diagnose, treat or relieve symptoms of a disease or abnormal condition.

Define crude drug?

Crude drug are define as the drug which are obtain from natural resources like plants, animals, minerals and they are used  as such as they occur in nature without any processing except drying and size reduction.  

Crude drugs are further grouped as organized (cellular) and unorganized (acellular), according to whether they contain a regular organized cellular structure or not.

Difference between organized drug and unorganized drug: 

Organized	Unorganized
As the name indicates, these are the organs of the plants or animals and are made up of cells or definite structure.	These are derived from plants or animals by some process of extraction, followed by purification, if necessary or may be a pathological product.
These are solid in nature.	These are solid/ semi-solid/ liquid in nature.
Botanical or zoological terminology can be used to describe these drugs.	Such terminologies are inadequate but physical characters such as solubility, density, optical rotation, refractive index are important for description.
Microscopic characters are important criteria for identification.	Chemical test and physical standards are important for their identification.
Eg: Digitalis. Cinchona, Clove, Fennel, Jalap, Ephedra etc.	Eg: Aloe, Agar, Opium, Castor oil, Beeswax, Gum Acacia etc.

 

Because of their wide distribution, the classification of drug in a particular sequence is necessary for easy understanding. For pharmacognostic study crude drugs are classified as follows -

•  Alphabetical classification.
• Chemical classification.
• Pharmacological classification.
• Morphological classification.
• Taxonomical classification.
• Chemo-taxonomical classification.  

Each of these systems of classification has its merits and demerits.

Alphabetical Classification -

 In this method, drugs are classified according to the first alphabet of their English or Latin name.-

 This classification is based on official books like:

• Indian Pharmacopoeia.
• United state Pharmacopoeia.
• British Pharmacopoeia.  

          Ex. Acacia, enzoin, Cinchona, Digitalis, Ergot, Fennel, Ginger, Hyoscyamamus, Ipecacuanha, Lalap, Kurchi, Liquorice, Mints, Nux- vomica, Opium, Quassia, Rauolfia, Senna, Tulsi, Vasaka, Wool fat, Yellow bees wax etc.

Merits: 

• Simple method.
• Easy and quick to use.
• The addition of drug entries is easy.
• If we know the name of the drug, we can study it properly.

 

Demerits:

• The nature of the crude drug is not known. i.e., Where it is organized or unorganized.
• This classification does not help in differentiating that drug obtain from plants and animals or mineral sources. 
• Difficult if there is change in name.

Chemical Classification -

The activity of crude drugs is due to the presence of certain chemical constituents in the drug. In this classification, crude drugs are classified according to their chemical constituents.

Chemical constituent	Drug
Alkaloids	Cinchona, Datura, Vinca, Ipecac, Nux- vomica.
Glycoside	Senna, Aloe, Ginseng, Glycyrrhiza, Digitalis.
Carbohydrates and derived products	Acacia, Tragacanth, Starch, Isabgol.
Volatile oil	Clove, Coriander, Fennel, Cinnamon, Cumin.
Resin and Resin combination.	Benzoin, Tolu Balsam, Balsam of Peru.
Tannins	Catechu, Tea.
Enzymes	Papain, Caesin, Trypsin.
Lipid	Bees wax, Lanolin.

Merits:

• If we Know the chemical constituents it is very easy to study the drug.
• It is a popular approach.

 Demerits:

• This method does not give any idea about the source of the drug.

• This type of classification fails in the proper placement of the drug which has more than one chemical constituent. i.e., Cinchona contains both alkaloids and glycoside. 

Pharmacological Classification - 

In this classification grouping the drugs are according to their pharmacological action. Crude drugs are classified according to the pharmacological action which is shown by their chemical constituents.

Pharmacological action	Drugs
Anticancer	Vinka, Podophyllum, Taxus
Anti- inflammatory	Colchicum, Turmeric
Anti- amoebic	Ipecac root, Kuruchi bark
Anti- asthmatic	Ephedra, lobelia
Antispasmodic	Dhatura, Hyocyamus
Astringent	Catechu
Analgesic	Opium
Bitter tonic	Quassia wood, Nux vomica
Carminattive	Coriander, Fennel, Clove, Peppermint
Purgatives	Senna, Rhubrab
Expectorant	Tulsi, Balsam of Tolu, Vasaka
Carido tonic	Digitalis, Squill

Merits:

• By this classification, it is very easy to study the drug.
• The medicinal importance of the drug is known easily.
• This classification is used for suggesting the substituents of the drug if it is nit available at a particular place or time. 

Demerits:

• If some crude drug have two different pharmacological actions then it is very difficult to classify then properly, i.e. Cinchona is tonic as well as anti- malarial and antipyretic.
• It does not give any idea where the drugs are organized or unorganized.
• It does not give any idea about the source of the drug. 

Morphological Classification -

Under this classification, the crude drugs are arranged according to the morphology or external characteristics of plants parts like roots, stems, seeds etc. The drugs which are obtained directly from the parts of the plant and contain cellular tissue are called organized drugs. A drug which is prepared from the plant by some intermediate physical process such as incision, or drying and does not contain any cellular plant tissue is called as unorganized drug. Aloe juice, Opium, Latex, gelatin, honey etc.

Part of Plants	Drugs
Leaves	Vasaka, Digitalis, Senna, Dhatura.
Barks	Cinnamon, Cinchona, Cascara, Ashoka.
Flowers	Clove, Pyrethrum, Artemisea.
seed	Linseed, Mustard, Isapgol, Nux vomica.
Fruits	Dill, Coriander.
Roots	Ipecacuanha, Rauwolfia, Aconite
Rhizomes	Rhubarb, Turmeric, Ginger.
Dried latex	Opium
Dried juice	Aloe.
Dried extracts	Agar, Catechu, Gelatin.
Gums	Tragacanth, Acacia, Guar gum.

Merits:

• A more convenient method for practical purpose.
• It gives an idea about the crude drug whether it is organized or unorganized.
• Morphological classification is more helpful to identify an detect adulteration.

Demerits:

• During collection, drying and packaging morphology of the drug changes, thus they are difficult to study by this method.
• Animals and marine drugs are difficult to classify by this method.
• Repetition of drugs and plants occurs.

Taxonomical classification - 

It is purely a botanical classification. In this system, drugs are arranged according to the plant from which they are derived in terms of phylum, family, class and species. 

                 Phylum : Spermatophyta

                   Division : Angiospermae 

                      Class : Dicotyledons 

                         Order : Rosales

                            Family : Leguminosae

                               Sub- family : Papilionaceae

Merits: 

• Drugs are easily arranged.
• Animal drugs are classified as arthropods and mammals.
• It is a more scientific method.

Demerits : 

• It does not give any idea about a chemical constituent.
• This system does not correlate with the therapeutic activity of the drug.

Chemo- Taxonomical Classification:

Chemotaxonomy establishes a relationship between position of the plant and attempts to utilize chemical facts for more understanding of the biological evolution and relationships.

                The characters more often studied in chemotaxonomy are secondary metabolites of pharmaceutical significance such as alkaloids, glycosides, flavonoids etc.

 

     Examples: 

• Plants of Umbelliferae contain volatile oil; 
• Plants of Solanaceae, Apocynaceae contain Alkaloids; 
• Sulphur containing compounds - Allium cepa, Allium sativum.
• Cardiac glycosides - Digitalis purpurea, Digitalis lanata. 

Merits :

•  It gives similarities of constituents between different plants species of same genus and same family.