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Classification of drugs (pharmacognosy:- 1) Notes


The most important natural sources of drugs are higher
plant, microbes and animals and marine organisms. Some
useful products are obtained from minerals that are both
organic and inorganic in nature. In order to pursue (or
to follow) the study of the individual drugs, one must
adopt some particular sequence of arrangement, and this
is referred to a system of classification of drugs. A method
of classification should be:

(a) simple,
(b) easy to use, and
(c) free from confusion and ambiguities.
Because of their wide distribution, each arrangement of
classification has its own merits and demerits, but for the
purpose of study the drugs are classified in the following
different ways:
1. Alphabetical classification
2. Taxonomical classification
3. Morphological classification
4. Pharmacological classification
5. Chemical classification
6. Chemotaxonomical classification
7. Serotaxonomical classification
Alphabetical Classification
Alphabetical classification is the simplest way of classifica-
tion of any disconnected items. Crude drugs are arranged
in alphabetical order of their Latin and English names
(common names) or sometimes local language names (ver-
nacular names). Some of the pharmacopoeias, dictionaries
and reference books which classify crude drugs according
to this system are as follows:
1. Indian Pharmacopoeia
2. British Pharmacopoeia
3. British Herbal Pharmacopoeia
4. United States Pharmacopoeia and National Formu-
5. British Pharmaceutical Codex
6. European Pharmacopoeia
In European Pharmacopoeia these are arranged according
to their names in Latin where in United States Pharmaco-
poeia (U.S.P.) and British Pharmaceutical Codex (B.P.C.),
these are arranged in English.

It is easy and quick to use.

There is no repetition of entries and is devoid of con-

In this system location, tracing and addition of drug
entries is easy.
There is no relationship between previous and successive
drug entries.
Examples: Acacia, Benzoin, Cinchona, Dill, Ergot,
Fennel, Gentian, Hyoscyamus, Ipecacuanha, Jalap, Kurchi,
Liquorice, Mints, Nux vomica, Opium, Podophyllum,
Quassia, Rauwolfia, Senna, Vasaka, Wool fat, Yellow bees
wax, Zeodary.
Taxonomical Classification
All the plants possess different characters of morphologi-
cal, microscopical, chemical, embryological, serological and
genetics. In this classification the crude drugs are classified
according to kingdom, subkingdom, division, class, order,
family, genus and species as follows.
Class: Angiospermae (Angiosperms) are plants that produce
flowers and Gymnospermae (Gymnosperms) which don’t
produce flowers.
Subclass: Dicotyledonae (Dicotyledons, Dicots) are plants
with two seed leaves; Monocotyledonae (Monocotyledons,
Monocots) with one seed leaf.
Superorder: A group of related plant families, classified in the
order in which they are thought to have developed their dif-
ferences from a common ancestor. There are six superorders
in the Dicotyledonae (Magnoliidae, Hamamelidae, Caryophyl-
lidae, Dilleniidae, Rosidae, Asteridae), and four superorders in
the Monocotyledonae (Alismatidae, Commelinidae, Arecidae, and
Liliidae). The names of the superorders end in –idae.
Order: Each superorder is further divided into several orders.
The names of the orders end in –ales.
Family: Each order is divided into families. These are plants
with many botanical features in common, and are the highest
classification normally used. At this level, the similarity
between plants is often easily recognizable by the layman.
Modern botanical classification assigns a type plant to each
family, which has the particular characteristics that separate
this group of plants from others, and names the family after
this plant.
The number of plant families varies according to the
botanist whose classification you follow. Some botanists
recognize only 150 or so families, preferring to classify other
similar plants as subfamilies, while others recognize nearly
500 plant families. A widely accepted system is that devised
by Cronquist in 1968, which is only slightly revised today.
The names of the families end in –aceae.
Subfamily: The family may be further divided into a number
of subfamilies, which group together plants within the family
that have some significant botanical differences. The names
of the subfamilies end in –oideae.
Tribe: A further division of plants within a family, based on
smaller botanical differences, bin still usually comprising many
different plants. The names of the tribes end in –eae.
Subtribe: A further division based on even smaller botanical
differences, often only recognizable to botanists. The names
of the subtribes end in –inae.
Genus: This is the part of the plant name that is most famil-
iar; the normal name that you give a plant—Papaver (Poppy),
Aquilegia (Columbine), and so on. The plants in a genus are
often easily recognizable as belonging to the same group.
Species: This is the level that defines an individual plant.
Often, the name will describe some aspect of the plant—
the colour of the flowers, size or shape of the leaves, or it
may be named after the place where it was found. Together,
the genus and species name refer to only one plant, and
they are used to identify that particular plant. Sometimes,
the species is further divided into subspecies that contain

Subject:- Pharmacognosy 1

Semester:- Sem 3

Course:- Bachelor of pharmacy