Classification of Crude Drugs in Pharmacognosy

The term crude generally applies to the products from plants & animal origin found in a raw form. however, the term is also applied to inclusion of pharmaceutical products from mineral kingdom in original form and not necessarily only of organic origin such as kaolin, bentonite etc. The term crude drug is referred in relation to the natural products that has not been advanced in value or improved in condition by an any process or treatment beyond that which is essential for its proper packing and prevention from deteriorating. Crude drugs are further grouped as organised (cellular) or unorganised (cellular) according to weather they contain a regular organised cellular structure or not. Organised drugs compromises those crude drug material which represent a part of the plant and are therefore made up of cells. Unorganised drugs are diverse group of solid & liquid materials which do not consist of parts of plant and are obtained from natural sources bya variety of extraction procedures.

In Pharmacognosy, the crude drugs may be classified according to their alphabetic status, taxonomy of plants and animals from which they are derived, their morphology, chemical nature of their active constituents, chemo taxonomical status and their pharmacological actions and therapeutic applications.

It should be noted that, none of these systems give total profile of natural drugs and have their own limitations

Alphabetical Classification

The crude drugs are arranged according to the alphabetical order of their Latin & English names. Some of the pharmacopoeias and reference books which classify crude drugs according to this system are as follows:

  1. Indian Pharmacopeia
  2. British Pharmacopeia
  3. British Herbal Pharmacopeia
  4. United States Pharmacopeia & National Formulary
  5. British Pharmacopeia Codex
  6. European Pharmacopeia (Latin title)

Example: Acacia, Benzoin, Cinchona, Dill, Ergot, Fennel, Gentian Hyoscyamus, ipecacuanha, Jalap, Kurchi, Liquorice, Myrrh, Nux-Vomica, Opium, Podohyllum, Quassia, Rauwolfia, Senna, uncaria gambier, vasaka, wool fat, yellow bees-wax, zedoary.

Taxonomical (Biological) Classification

The drug are classified according to plants or animals from which they are obtained in phyla,orders, families, genera, subspecies etc. This method of classification is based on the consideration of natural relationship or phylogeny among plants or animals. The crude drugs of plant origin are classified on the basis of one of the accepted system of botanical classification. A large number of plant families have certain distinguishing characteristics that permit crude drugs from these families to be studied at one time. Thus, drugs obtained from plants having alternate leaves, cymose, flowers and fruit that are berries or capsules (hyoscyamus, datura, belladonna & stramonium) are considered with other phylogenetic types. This system of classification is criticized for its failure to recognise the organised and unorganised nature of crude drug. At first sight, this classification looks appealing, but many drugs are not entire plants and represent parts of the plants that have been processed systemically. Further, the system fails to take into an account chemical nature of active constituents and therapeutic significance of crude drugs.

The Taxonomical classification for few crude drugs derived from dicot plants is as follows:

GenusGlycyrrhiza, Astragalus, Myroxylon
SpeciesGlyxyrrhiza glabra, Astragalus gurmmifer, Myroxylon balsamum
GenusAtropa, Hyoscyamus, Datura
SpeciesHyoscyamus niger, Datura stramonium, Atropa belladonna
SpeciesClaviceps purpurea

Morphological Classification

The crude drugs are grouped according to the part of the plant or animal represented into organised and unorganised drugs. The organised drugs are divided into parts of plants like leaves, flowers, fruit, seeds, woods, barks and subterranean parts like roots and rhizomes. The unorganised drugs are dried latex, gums, extracts etc. Some of the examples of crude drugs under this type of classification are as follows.

SeedsNux-vomica, Strophanthus, Isabgol, Castor
LeavesSeena, Digitalis, Vasaka, Eucalyptus
BarksCinchona, Kurchi, Cinnamon, Quaillaia
WoodsQuassia, Sandalwood, Sassafras, Red sanders
RootsRauwolfia, Ipecacuanha, Aconite, Jalap
RhizomesTurmeric, Ginger, Valerian, Podophyllum
FlowersClove, Pyrethrum, Artemisia, Saffron
FruitsCoriander, Colocynth, Fennel, Bael
Entire DrugEphedra, Ergot, Cantharides, Belladonna
Dried laticesOpium, Gutta-percha, Papain
Resin & Resin CombinationBalsam of Tolu, Myrrh, Asafoetida, Benzoin
Dried JuicesAloes, Kino, Red gum
GumAcacia, Tragacanth, Ghatti gum, Guar gum
Dried extractsGelatin, Catechu, Agar, Curare

This system of classification is more convenient for practical study especially when the chemical nature of drug is not clearly understood.

Chemical Classification

The crude drugs are divided into different groups according to the chemical nature of thier most important constituent. Since the pharmacological activity and therapeutics significance of crude drugs are based on the nature of this chemical constituents, it would appear that chemical classification of crude drugs is the preferred method of study. The crude drugs containing alkaloids are grouped together, regardless of their morphology and taxonomical relationship. Free examples of the drugs ummey chemical classification are as follows

GlycosidesDigitalis, Senna, Cascara, Liquorice
AlkaloidsNux-Vomica, Ergot, Cinchona, Datura
TannisMyrobalan, Pale catechu, Ashoka
Volatile OilsPeppermint, Clove, Eucalyptus, Garlic
Lipids, Carbohydrate & derived productsAcacia, Agar, Guar Gum, Pectin, Honey, Ispaghula
Resins & Resin CombinationColophony, Jalap, Balsam of Tolu
Vitamins & hormonesYeast, Shark liver oil, Oxytocin, Insulin
Protein & EnzymesCasein, Gelatin, Papain, Trypsin

The crude drugs belonging to different morphological or taxonomical categories may be brought together, provided there is come similarity in the chemical nature of active principles.

Pharmacological (Therapeutics) Classification

This system of classification involves the grouping of crude drugs according to the pharmacological action is their chief active constituent or their Therapeutic uses. Regardless of morphological, taxonomical status or chemical relationship, the drugs are grouped together, provided they exhibit similar pharmacological action. Thus cascara, castor oil, senna, jalap, colocynth are grouped together as purgatives or laxative because of their common pharmacological action. Similarly gentian, cinchona, nux vomica and swertia are grouped together, eg: bulk purgatives, irritant purgatives, emollient purgatives etc. Some of drugs could be classified under your pharmacological headings since they exhibit two different actions. For example: cinchona is classified both as antimalarial and bitter tonic. An outline for pharmacological classification of crude drugs is as follows

1) Drugs acting on gastro intestinal tract

BitterGentian, Quassia, Cinchona
CarminativesDill, Mentha, Cardamom
Anti-AmoebicsKurchi, Ipecacuanha
Bulk LaxativesAgar, Ispaghula, Banana
PurgativesSenna, Castor oil
Peptic ulcer treatmentDerivatives of glycyrrhetinic acid(liquorice), Raw Bananna

2) Drugs acting on respiratory system

ExpectorantsLiquorics, ipecacuanha, Vasaka
AntiexpectorantsStramonium leaves (Atropine)
AntitussivesOpium (Codein, Noscapine)
BronchodilatorsEphedra, Tea (Theophylline)

3) Drugs acting on cardiovascular system

CardiotonicsDigitalis, Squill, Strophanthus
Cardiac DepressantsCinchona (Quinidine), Veratrum
Vasco constrictorsErgor (Ergotamine), Ephedra

4) Drugs acting on autonomic nervous system

CholinergicsPhysostigma, Pilocarpus
Anti-CholinergicsBelladonna, Datura

5) Drugs acting on Central nervous system

Central AnalgesicsOpium (Morphine)
CNS StimulantsCoffee (Caffeine)
AnalepticsNux-Vomica, Lobelia, Camphor
CNS DepressantsHyoscyamus, Belladonna, Opium (Morphine, Codeine)
HalluciogenicsCannabis, Poppy Latex

6) Antispasmodic

Smooth muscle relaxantsOpium (Papaverine), Datura, Hyoscyamus
Skeletal muscle relaxantsCurare

7) Anti-Cancer: vinca, podophyllum, camptotheca, taxus

8) Antirheumatics: aconite, colchicum, guggul

9) Antihelmintics: Quassia, male fern, vidang

10) immuno modulatory agents: Ashwagandha, Tulsi, Ginseng, Asparagus, picrorrhiza kurroa.

They modulate immune response and principally include immunosuppressive agents and also biological response modifiers which act by immuno stimulation.

11) Drugs action on skin and mucous membrane: Olive oil, wool fat, bees wax, archis oil, sesame oil, balsam of tolu, balsam of peru.

12) Astringents: myrobalan, black catechu

13) antimalarials: cinchona, Artemisia

14) immunising agents: vaccine, sera, toxoids, antitoxins.

15) Drugs acting chemotherapeutically : antibiotics

16) local anaesthetic: coca

Chemotaxonomic Classification

The expanding knowledge of phytochemical screening had revealed the exercise of close relationship between constituents of plants and their taxonomical status. The ‘chemotaxonomy’ had brought the plants chemist back to systematic botany in view of the facts that certain compounds have been found to characterise certain groupings. Chemotaxomy establishes a relationship between position of plant and attempts to utilise chemical facts for more exact understanding of biological evolution and relationships. The characters more often studied in chemotaxomy are secondary metabolites of pharmaceutical significance such as alkaloids, glycosides, flavonoids etc. The knowledge of chemotaxomy could serve as the basis for classification of crude drugs. The location of berberin alkaloids in hydrastics, berberis and argemone, distribution of rutin, ranunculaceous alkaloids and flavonoids in species of higher plants are of chemotaxomical significance. DNA hybridization, amino acid sequencing in proteins and serotaxonomy are also gaining significant in this method of Classification.