1. ISOLATION, PURIFICATION
AND SCREENING OF PLANT
CONSTITUENT S
DR.U.SRINIVASA. M.Pharm,
Ph.D

2. INTRODUCTION
 The use of plant-derived medicinal dates back
many centuries although it is still under estimation
in modern medicine.
 Plants remain the most important source of
natural drugs. More than 30% of prescription
drugs are natural products.
 More than 60% of anticancer and anti-infective
drugs are natural products.

3. SOURCES OF DRUGS
1.Natural substances: From plants,
microorganisms, animals etc. (totally obtained
from nature).
2. Semi synthetic substances: These are
drugs that are manufactured by partial synthesis.
3. Synthetic substances: These are drugs
which are manufactured by total synthesis (i.e.
complete synthetic process or processes)

4. MEDICINAL PLANTS INFORMATION
SOURCES :
 Information, however can be obtained from one
or more of the following sources:
1- Herbals
2- Medical botany
3 - Ethnobotany
4 - Herbaria (herbarium)
5 - Field exploration
6 - Phytopharmacological surveys

5. PHYTOCHEMICAL SCREENING –
To carry phytochemical screening the following points
must be fulfilled:
1- Selection of promising plant materials.
2- Proper collection of selected plants.
3- Authentication of plant material.
4- Drying of plant materials.
5- Grinding of the dried plants.
6 - Garbling of the dried plants
7 - Packing, storage and preservation
8 - Extraction and fractionation of constituents.
9 - Methods of separation and purification.
10 - Methods of identification of isolated compounds
(Structure elucidation e.g. UV, IR, MS, H-NMR and C-NMR)

6. SELECTION OF PROMISING PLANT
MATERIALS:
 Before investing time, effort and money in
phytochemical screening it is very important to
select a promising plant.
 The choice of promising plant depends upon the
following:
1- A plant which have a biological activity.
2- A plant used in folk medicine.
3- A plant which show a particular toxicities

7. IDENTIT Y
 Identity can be achieved by macro- and
microscopical examinations. Voucher specimens
are reliable reference sources. Outbreaks of
diseases among plants may result in changes to
the physical appearance of the plant and lead to
incorrect identification. At times an incorrect
botanical quality with respect to the labeling can
be a problem.

8. PROPER COLLECTION OF SELECTED PLANTS
Drug may be collected from:
1 - Wild plants. 2 -
Cultivated plants.
Wild plant Cultivated plant
Disadvantage Advantage
Scattered in large or Present in limited area
unlimited area
Difficult to reach Easy to reach
The collector must be The collector must not be
highly skilled botanists skillful person
Deficiency may occur due Continuous supply
to continuous collection

9.  The following precautions should be
considered during stage of collection :
1 .The proper time of the day, time of the year and maturity
stage of collection is particularly important because the
nature and quantity of constituents may vary greatly in
some species according to the season and time of
collection
2.The collected plant should be free from any
contamination.
3.Collecting plants which are free from diseases (i.e. which
are not affected by viral, bacterial, fungal infection).

10. Authentication of plant material : This
may be confirmed by:
1. Establishing the identity by a taxonomy experts.
2.Collection of a common species in their expected
habitat by a field botanist.
3. By comparing the collecting plant with a voucher
specimen ( herbarium sheet).

11. Drying of plant materials
Aim of drying:
1. Ease of transport.
2. Ease of grinding
3. Inhibit the growth of microorganisms.
4. Preservative of active constituents.
Drying is done in:
Shade and in sunlight (Natural drying).
Hot air drying or by freeze-drying (Artificial drying).

12. Extraction and fractionation of
constituents :
There is no general (universal) method for the
extraction of plant materials.
The precise mode of extraction depends on:
1- The texture of the plant material.
2- The water content of the plant material.
3- The type of substances to be extracted or nature
of active constituents.

13. EXTRACTION:
Is the separation of medicinally active portion of
plants or animal tissues through the use of
selective solvent and suitable methods extraction.
The principal methods of extraction are:
1 - Macération
2 - Percolation
3 - Infusion
4 - Decoction
5 - Digestion

14. 5 - Digestion
6 - Continuous hot extraction ( Soxhlet extraction
procèss).
7 - Liquid-liquid extraction
8 - Solvent-solvent ppt.
9 - Distillation

15. MACERATION :
1.In maceration powdered drug is soaked in
organic solvent and kept for about 24 hrs ,
sometimes 3-4 days also, depending upon the
part of the plant to be extracted.
2.The solvent is decanted, filtered and
concentrated.

16. PERCOLATION :
In percolation special types of percolators are used.
These are funnel shaped. The solvent continuously
percolates through , the coarse particles of the
drug. Solvent is collected, filtered and
concentrated.

17. DECOCTION :
In case of decoction , the powdered plant material
is boiled with the solvents .It is collected and
filtered. Filtered solvent is concentrated.
Eg. Preparation of tea.

19. Continuous hot extraction technique (Soxhlet
extraction procèss )

20. Successive solvent extraction :
Petroleum ether (60-80)
Benzene
Chloroform
Acetone
Ethanol (95%)
Chloroform water