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28 Textbook of Pharmacognosy
the information on various aspects of crude drugs was pouring in different
types of classification procedures were framed. The drugs are classified in
different ways like: Alphabetical classification, morphological classification,
taxonomic classification, pharmacological classification, chemical
classification, chemotaxonomical classification and serotaxonomical
classification in addition to biochemical and geographical classifications.
ALPHABETICAL CLASSIFICATION
This is the simplest way of classification for disconnected materials. The
crude drugs are generally arranged in an alphabetical order of their Latin
and English common names or local language (vernacular) names. This
system is found in Indian Pharmacopoeia, British Pharmacopoeia (in
English – 1993), British Herbal Pharmacopoeia (1990), British Herbal
Compendium (1992), United States Pharmacopoeia and National
Formulary, British Pharmaceutical Codex, European Pharmacopoeia (in
Latin – 1980) and Encyclopedia of Common Natural Ingredients used in
Drugs and Cosmetics. The merits of this classification are: this method is
easy and very quick to use, entries are not repeated thus avoiding confusion
and location of the drug, traceability and addition of new entries becomes
easier. This system has its own demerit that it lacks relationship between
the previous and successive entries into it. This system is the most little
disputed system. This method has been adopted in some modern books of
materia medica like Reutter’s ‘Traite de Matiere Medicale et de Chimie Vegetale’
published in Paris (1923).
The alphabetical arrangement of drugs can be exemplified by: Acacia,
agar, alumina, belladonna, benzoin, cinchona, cinnamon, cod liver
oil, Colchicum, cuprum (copper), Datura, Digitalis, ergot, fennel, ferrum
(iron), gentian, henna, honey, hydragyrum (mercury), Hyoscyamus,
Ipecacuanha, jalap, kaolin (china clay), kurchi, kalium (potassium), linum,
liquorice, musk, myrrh, nux vomica, opium, ox gall, Podophyllum, Rauwolfia,
rhubarb, saffron, senna, tobacco, vasaka, white wax, wool fat, yellow bees
wax, etc.
MORPHOLOGICAL CLASSIFICATION
The crude drugs are arranged according to the external characters of the
different parts of the plants or animals which are to be used as a drug.
These may be organised or unorganised drugs. The organised drugs are the
direct parts of the plants or the animals containing the cellular tissues which
can be easily identified by their appearance, while the unorganised drugs
are of plant, animal or mineral origin without any defined cellular structure
prepared by intermediate physical processes like incision, drying or
extraction with a solvent and cannot be easily identified by their
Classification of Crude Drugs 29
morphology. The merits of this type of classification is that identification
becomes easier so also the detection of any adulteration. At the same time,
this is more convenient for the practical study. The main drawback of this
classification is that there is no correlation of the chemical constituents
with their medicinal action, and also there may be a possibility of drug
repetition. Dr. T.E. Wallis, a great exponent of this classification is of the
view that the drugs should always be classified according some inherent
or intrinsic properties.
The organised drugs include:
• Barks of cinchona, cinnamon, quaillaia and wild cherry
• Leaves of digitalis, senna, eucalyptus and vasaka
• Seeds of nux vomica, isphagul, castor and linseed
• Fruits of fennel, coriander, strychnos, colocynth and bael
• Woods of red sanders, sassafras and sandalwood
• Roots of rauwolfia, boerhavia, ipecac and aconite
• Rhizomes of ginger, turmeric, and podophyllum
• Flowers of saffron, clove, china rose and artemisia
• Entire drugs of ephedra, ergot, centella, catharanthus and belladonna,
etc.
The unorganised drugs include:
• Gums like acacia, gutty gum, guar gum, and gum tragacanth
• Extracts of agar and pectin, gelatin, honey
• Dried latex of opium, papain
• Resins of myrrh, asafoetida, balsam and benzoin
• Dried juice of kino and aloe
• Dried extracts of catechu, curare, etc.
TAXONOMICAL (BIOLOGICAL) CLASSIFICATION
This classification is purely botanical as it is based on the principles of
natural relationship and evolutionary development. The entire plant is not
used as a drug and it is only a part of the plant which is used. Hence, this
has no significance and does not help in assigning the plants into a specific
taxonomic group. This system only helps in the study of evolutionary
development. This fails to correlate between the chemical constituents of
the drugs and their biological activity. The knowledge of botany and
zoology is always necessary to classify the drugs in this way.
The drugs belong to many groups and families of plant kingdom such
as algae and fungi (thallophyta), pteridophyta, pinaceae and ephedraceae
(gymnosperms), gramineae, liliaceae, zingiberaceae, iridaceae,
dioscoriaceae, araceae and orchidaceae (monocotyledons), and over
30 Textbook of Pharmacognosy
100 families of dicotyledons. Animal drugs mainly come from many
invertebrate and vertebrate groups.
Under this system, crude drugs like liquorice can be classified as:
• Regnum: Vegetabile
• Division: Magnoliophyta
• Class: Magnoliopsida
• Subclass: Rosidae
• Order: Fabales,
• Family: Fabaceae
• Genus: Glycyrrhiza
• Species: glabra.
This classification may appear to be interesting but it fails to recognise
whether the drug is organised or unorganised and it does not give any
indication of the part from which the drug is produced. Also it fails to
denote the chemical nature of the active principle and its therapeutic
significance.
PHARMACOLOGICAL (THERAPEUTIC OR PHYSIOLOGICAL OR PHARMACODYNAMICAL) CLASSIFICATION
In this type of classification, the drugs are grouped in accordance with
their action on the body of the organism or their important constituent or
therapeutic use. The method is the most widely followed method and
appears to be more relevant. Drugs possessing a common therapeutic action
are grouped together irrespective of the morphology of the part or their
phylogenetic relationship or the nature of their constituents. This becomes
useful in suggesting the appropriate substitutes in case of their nonavailability. The most important demerit of such a classification is that the
drugs with different therapeutic action are classified into more than one
group which results in an ambiguity and confusion.
The drugs are grouped under specific headings in this type of
classification such as:
• Carminatives (mentha and cardamom)
• Emetics (ipecac)
• Antiamoebics (kurchi and ipecac)
• Laxatives (agar, ispaghul and banana)
• Purgatives (senna, plantago, cascara and castor oil)
• Expectorants (licorice, ipecac and vasaka)
• Antitussives (opium)
• Bronchodilators (ephedra and tea)
• Astringents (black catechu, tannic acid, myrobalan and ashoka bark)
• Cardiotonics (digitalis and squill)
Classification of Crude Drugs 31
• Cardiac depressants (cinchona and veratrum)
• Peripheral vasoconstrictors (ergot and ephedra)
• Antihypertensives (rauwolfia)
• anticholinergics (belladonna and Datura)
• Central nervous system stimulants (coffee)
• Central nervous system depressants (hyoscyamus, belladonna and
opium)
• Analeptics (nux vomica, camphor and lobelia)
• Hallucinogenics (latex of cannabis and poppy)
• Antispasmodics (opium and curare)
• Anticancerous (vinca, podophyllum and taxus)
• Antirheumatics (aconite, colchicum and guggul)
• Anthelmintics (quassia and male fern)
• Antimalarials (cinchona and artemisia)
• Local anaesthetics (cocoa)
• Immunizing agents (vaccines, sera, toxoids and antitoxins)
• Immune-modulatory agents (aswagandha, ginseng, asparagus and
picrorhiza), etc.
CHEMICAL CLASSIFICATION
As the pharmacological activity and the therapeutic significance of the
crude drugs are based on the nature of the chemical constituents, the drugs
are divided into different groups in accordance with their chemical
nature in this method. This system is mainly dependant on creation of the
groups with identical chemical constituents. This system is useful in the
phytochemical studies of the constituents. But, this may result in an
ambiguity when a particular drug possesses many compounds that belong
to different groups. The drugs belonging to different morphological or
taxonomic categories may be brought together provided there is some
similarity in the chemical nature of the active principles. Some of the
important chemical substances are alkaloids, glycosides, tannins, resins,
volatile oils, fixed oils, etc.
This system can be exemplified by:
• Glycosides (digitalis, senna, licorice, aloe, cascara, scilla, dioscroea,
ginseng, senega, tobacco, glycyrrhiza and rhubarb)
• Alkaloids (ergot, cinchona, Datura, rauwolfia, nicotiana, piper,
belladonna, hyoscyamus, withania, calumba, nux vomica,
catharanthus, vasaka, aconite, holarrhena, punarnava, shankhpushpi
and opium)
• Tannins (myrobalan, ashoka, pale catechu, black catechu, Behera and
Amla)
32 Textbook of Pharmacognosy
• Volatile oils (turpentine oil, peppermint oil, mentha oil, lemongrass
oil, clove oil and Eucalyptus oil)
• Lipids represented by fixed oils, fats and waxes (castor oil, sesame oil,
chalmoogra oil, almond oil, corn oil, coconut oil, palm oil, mustard
oil, soya oil, safflower oil, sunflower oil, chenopodium oil, lanolin,
bees wax, kokum butter, shark liver oil and cod liver oil)
• Ccarbohydrates (starch, sodium alginate, cellulose, pectin)
• Triterpenoids (rasna, pluchea and vanda)
• Esters (pyrethrum)
• Soluble carbohydrates (honey)
• Organic acids (tamarind)
• Gums (gum acacia, guar gum, gum tragacanth and sterculia gum)
• Mucilages (isphagul seed and bark, linseed, and agar)
• Resins (jalap, colophony, balsam of peru, storax, vidang, myrrh,
asafoetida, and ginger)
• Minerals (kaolin and tar)
• Vitamins and hormones (yeast, shark liver oil, oxytocin and insulin),
• Proteins (gelatin and yeast)
• Enzymes (casein, trypsin and papaian), etc.
CHEMOTAXONOMIC CLASSIFICATION
This classification mostly relies on the chemical similarity of a taxon and is
based on the relationship between the constituents in different plants.
Specific classes of plants show specific chemical constituents as such an
entirely new concept of chemotaxonomy that utilises the chemical
characters in understanding the taxonomical status of the individual, its
relationship with other plants and the evolution arises. This system gives
a much wider scope in understanding the interrelationship between the
chemical constituents, biosynthesis and possible action. The chemical
constituents of certain type are the characteristic of certain groups of plants
like tropane alkaloids in majority of the members of solanaceae and volatile
oils in the members of umbelliferae show that there is some definite
relationship between the chemical constituents and the taxonomical status
of the plants. The characters often studied in chemotaxonomy are the
secondary metabolites of medical significance like alkaloids, glycosides,
flavonoids, etc. The alkaloids in Hydrastis, Berberis and Argemone, and
distribution of the alkaloids in ranunculaceae and flavonoids in higher
plants are of significance in chemotaxonomy. Hybridisation of DNA,
sequencing of amino acids in proteins and serotaxonomy are gaining greater
significance in chemotaxonomic classification.
In addition to these, biochemical classification and geographical
classification are also being followed. The biochemical classification appears
Classification of Crude Drugs 33
to be more natural in modern pharmacognosy as it takes into account the
biogenetic relationship of the natural orders. The geographical classification
is based on the availability of the drugs in different parts of the world, as
all the drugs do not grow everywhere. Prof. E. Schratz of Germany, a strong
supporter of the geographical, commercial and political roles of drugs,
taught pharmacognosy through this classification under a caption
‘Wirtsschaftliche Geograsphie’.
SEROTAXONOMICAL CLASSIFICATION
Serology is defined as the unit of biology which is concerned with the nature
and interactions of the antigenic material and antibodies (the study of the
antigen-antibody reaction). It is defined as the study of origins and properties of
antisera (Smith, 1976). When the foreign cells (or particles–antigens) are
introduced into an organism, the antibodies are produced in the blood
(antiserum). The substance that is capable of stimulating the formation of
an antibody is called the antigen, and a specific protein molecule produced
by plasma cells in the immune system in response to an antigen is called
an antibody. The antibodies combine chemically with specific antigens and
such a combination elevates an immune response. The application of
serology in solving the problems in taxonomy is called serotaxonomy.
Nuttal (1901) was the first biologist to compare the immunochemical
specificity of the serum proteins for systematic purposes. Later, Dunbar
(1910) showed that theta-proteins from the pollen, seeds and the leaves
were serologically distinct. Gholke (1914) established serology school in
Germany and later Germany became the centre of serological studies in
the world.
Phytoserology deals with the immunological reactions between the serum
antibodies and the antigens, has established itself as a valid method in
taxonomy because it helps to detect the homologous proteins. It uses the
specific properties of the antisera produced by the animals against proteins
as characters to assess the plant relationships. This branch of systematics
(serotaxonomy) developed and became popular first in Germany since the
beginning of this century.
According to Serotaxonomy, the classification of very similar plants by
means of the differences in the proteins they contain. The technique is based
on the highly specific relationship between the antigens and the antibodies
produced in response to them. The protein extracted from a plant is injected
into the blood of an animal, where it behaves as an antigen. After an interval
for the production of the antibodies, a blood sample is taken, and this can
be used to compare the first plant protein (antigen) with extracts taken
from other plants.
The process of serotaxonomy involves the following steps: The antigen
(the protein extract of the plant origin) is extracted. This is injected into the
34 Textbook of Pharmacognosy
bloodstream of an experimental animal to generate the antibodies. The
experimental animal produces the specific antibodies in response to the
antigen. The serum with the antibodies is called the antiserum. This is made
to react in vitro with the antigenic protein as well as the proteins of other
taxa whose affinities are to be determined. The amount of precipitation
shows the degree of homology. For example, to know the closeness of the
taxon A with taxons B, C, D and E, the proteins from taxon A are extracted
and are injected into the experimental animal (such as rabbit or mice). The
animal in return, produces the antibodies, which are extracted from the
blood of the animal as antiserum. When this is allowed to react with the
original protein extract from taxon A, complete coagulation takes place.
When this antiserum is allowed to react with the protein extracts from the
other taxa (B, C, D and E), the degree of coagulation varies. These degrees
of coagulation are compared to know the closeness of the taxa, e.g. more
the degree of coagulation, more is the closeness of the taxa.
The initiation of an immunological reaction in plants occurs as follows:
The antiserum gives a precipitation reaction with the plant extract (antigenantibody reaction), and the similarity of other species to the first one can
be assessed by measuring the amount of coagulation it causes.
The quantitative precipitation in solution is frequently replaced by the
more convenient methods like gel diffusion method, immunoelectrophoresis, radioimmunoassay and ELISA. The absorption protein
mixtures of different plants often contain some common proteins. The
removal of the antibodies for the common proteins from the antiserum is
carried out, and the logical comparisons can be drawn from the
precipitation reactions, as the antiserum at this juncture contains only those
antibodies which can react with the specific proteins. Immunoelectrophoresis is a combination of serological and electrophoretic
procedures. Primarily, the antigens are separated by electrophoresis on a
gel and then allowed to diffuse towards the antiserum. This method is
more specific as better antigenic separations occur during the process. In
Radioimmunoassay, the antigens or the antibodies are labelled with
radioactivity which facilitates their identification, even though they are in
small concentrations. In ELISA (Enzyme-Linked-Immunosorbent Assay),
the enzymes couple their catalytic activity with a specific immunoglobulin,
which forms the basis for the estimation. In tests like ELISA which involve
the labelling of either the antigens or the antibodies and linking this with
enzymes for detecting them even in minute quantities.
The importance of serotaxonomy is as follows: The use of serological
techniques to compare the proteins extracted from different plants is
an important aid in plant taxonomy. The serological data was used in
the classification of the orders and the assignment of the families in
Apiales, Fagales, Magnoliales, Juglandales, Rubiales, Ranunculales, etc.
Classification of Crude Drugs 35
(Fairbrothers, 1983). Six species of Bromus were separated on the basis of
the serological data (Fairbrothers and Jhonson, 1959). Fairbrothers and
Jhonson on the basis of their serotaxonomic studies showed that the genera
Magnolia and Michelia show closest affinity within the family Magnoliaceae.
Simon (1971) demonstrated the close relationship between Nymphaeceae
and Nelumbonaceae on the basis of serological data. Klos applied
serotaxonomic data in the classification of Leguminosae.
REVIEW QUESTIONS
1. Essay and Short Answer Questions:
1. Write an account of systems of classification of crude drugs with
examples.
2. What are the different types of classification of crude drugs that are
in practice today? Explain any two methods with examples.
3. How are the crude drugs classified? Add a note on the merits and
demerits of different classification systems.
4. Write short notes on the chemical and chemotaxonomic systems of
classification of crude drugs with examples.
5. Write short notes on the therapeutic and biological systems of
classification of crude drugs with examples.
6. Write short notes on the alphabetical and morphological systems
of classification of crude drugs with examples.
7. Name the different types of classification of crude drugs. Bring out
the differences between the organised and unorganised drugs with
examples.
8. How are the crude drugs classified? Bring out the differences
between pharmacodynamical and chemical systems of
classification with examples.
2. Choose the Correct Alternative:
1. Alphabetical classification is followed in: [ ]
a. British herbal compendium
b. European pharmacopoeia
c. Indian pharmacopoeia
d. All these
2. Pick out an organised drug from the following: [ ]
a. Wood of Sassafras b. Gelatin
c. Juice of aloe d. Benzoin
3. Pick out an unorganised drug from the following: [ ]
a. Rhizome of turmeric b. Ergot
c. Guar gum d. Fruit of bael
36 Textbook of Pharmacognosy
4. Which one of the following is used as an emetic? [ ]
a. Datura b. Ephedra
c. Tannic acid d. Ipecac
5. Pick out the cardiac depressant: [ ]
a. Liquorice b. Cascara
c. Cinchona d. Kurchi
3. Fill in the Blanks:
1. Latex of cannabis is used as a ...............................................................
2. The drugs from tobacco are alkaloids while those from Scilla are
......................................
3. Kaolin and tar are minerals while gelatin is a .....................................
4. Kokum butter is a lipid while pectin is a .....................................
5. Asafoetida is a resin while catechu is a .....................................
4. True or False Statements:
1. The simplest classification for disconnected drugs is alphabetical
system. [True/False]
2. Barks, leaves and the seeds represent unorganised drugs.
[True/False]
3. The unorganised drugs are not represented by the gums, resins and
juices. [True/False]
4. Taxonomical classification fails to correlate between the chemical
constituents and their biological activity. [True/False]
5. Therapeutic classification is the most widely followed and a more
relevant method. [True/False]
6. Chemical classification is useful in the phytochemical studies of the
drug constituents. [True/False]
7. The secondary metabolites of medical significance are studied in
chemotaxonomy. [True/False]
5. Match the following:
1. Oxytocin [ ] a. Honey
2. Papain [ ] b. Volatile oil
3. Soluble carbohydrate [ ] c. Hormone
4. Tamarind [ ] d. Enzyme
5. Turpentine [ ] e. Organic acids
4
Cultivation, Collection,
Processing, Drying and
Storage of Medicinal Plants
INTRODUCTION
India is one of the richest countries in the world with regard to the genetic
resources of medicinal plants. The land mass of India is only 2% but it has
11% of the total known world flora and is acclaimed as one of the top
12 mega diversity nations in the world. The agroclimatic conditions of India
are very conducive for introduction and domestication of new exotic plant
varieties. The Indian systems of medicine use over 2000 medicinal plants,
about 700 in Ayurveda, about 600 in Siddha medicine and about 700 in
Unani system of medicine. At present, the demand and the supply of the
medicinal plants is mismatching, and about 90% comes from the forests
while only 10% is from cultivation. The tribes and local communities living
in and around the forests are allowed to collect the minor forest products.
A lot of herbal products go uncollected and lost due to non-identification.
The availability of medicinal plants in nature has been depleted over the
years due to unscientific, unsustainable and discriminative collection and
some of the species have become scarce due to overexploitation. The
availability of the valuable medicinal plants has been reduced due to the
rapid expansion of the area under the cultivation of food and commercial
crops, the rapid conversion of non-forest area for other use and degradation
of the forest due to fire and grazing, etc. These practices have led to the
extinction of many valuable medicinal plants and some others have become
endangered. Hence, sincere efforts are needed for the reintroduction of
medicinal plants and eco-restoration for enhancing their availability. The
species which are exposed to the threat of their existence should be properly
identified and immediate steps should be taken for their conservation by
in situ and ex situ programmes and the development of herbal sanctuaries
to safe guard the biological wealth will be very helpful and also useful.
The cultivation for the domestication of medicinal plants at present is being
dictated by the user industries and they are fixing up the price of the
commodity. The essential factor is to go in for quick disposal and for a fair
37