2. • Introduction:
(1) Drug evaluation may be defined as the
determination of identity, purity and quality
of a drug.
(2) Identity – identification of biological source
of the drug.
(3) Quality – the quantity of the active
constituents present.
(4) Purity – the extent of foreign organic material
present in a crude drug.
(5) It was proposed by W.H.O
3. • Methods of Drug Evaluation:
The evaluation of a drug is done by studying
its various properties.
The various types of evaluation are :
(1) Morphological evaluation
(2) Microscopical evaluation
(3) Biological evaluation
(4) Chemical evaluation
(5) Physical evaluation
(6) Toxicological evaluation.
4. 1. MARPHOLOGICAL EVALUATION (organoleptic):
This refers to the drug evaluation by means of our
sense organs like odour, taste, smell.
Study of Gross Morphology:
• It includes the visual examination of drug.
• These drugs are classified into the following
groups.
Underground structures
Leaves
Flowers
Fruits
Seeds
Herbs
5. Underground Structures:
• Rhizomes, Roots, Bulbs, Corm and Tubers are
the underground structures of the plants.
• Examples: Ginger, Turmeric.
• Underground storage roots used as drugs are:
6. Leaves:
• The shape, margin, base, apex and venation of
leaves help in the identification of the drugs.
Senna leaves Tulasi
leaves
8. (b) Study of Sensory Characters:
• Colour, Texture, Odour and Taste are useful in
the evaluation of drugs.
Colour
Odour
Taste
9. Colour:
• Some drugs are green in colour when dried in
shade.
• But they become pale and bleached when
dried in sunlight.
Terminalia chebula - Fresh and Dried
10. Odour:
• Mentha, clove are some of the examples for
the drugs which have a distinct odour.
Taste:
• The drugs may be evaluated by taste also
Ex: Ginger, capsicum
11. II. Microscopic or Anatomical Evaluation:
• This method allows a more detailed
examination of a drug and it can be used to
identify organised drugs by their known
histological characters.
12. • Microscope can also be used for a quantitative
evaluation of drugs and adulterated powders.
• This is done by counting a specific histological
feature such as,
Stomatal Number
Stomatal Index
Vein-islet Number
Palisade Ratio
Quantitative Microscopy
Refractive Index
13. Stomatal Number:
• The average number of stomata present per
square millimeter of the epidermis is known
as stomatal number.
• Example: Datura – 141 (upper epidermis)
14. Stomatal Index:
• It is the percentage proportion of the number
of stomata to the total number of epidermal
cells.
• Stomatal number varies considerably with the
age of the leaf but stomatal index is relatively
constant for a given species.
• Example: Atropa – 20.0-23.0 (lower epidermis)
15. Vein-islet Number:
• Vein-islet number is defined as the number of
vein-islets per sq.mm. of leaf surface.
• It is constant for a given species of the plant. It
is irrespective with the age factor.
• Example: Cassia senna (26).
16. Palisade ratio:
• It represents the average number of palisade
cells beneath one epidermal cell, using four
continuous epidermal cells for the count.
• It is determined from powdered drugs with
the help of camera lucida.
• Example: Atropa belladona – 06-10
17. 3. PHYSICIAL EVALUATION:
• All the physical properties are useful in detection
of constituents present in a plant or herbal drug.
• A few of them are:-
Moisture Content
Viscosity
Melting point
Optical Rotation
Refractive Index
Ash Content
Extractive values
Volatile oil Content
Foreign organic matter
18. Moisture Content:
• Loss on drying
• Azeotropic method
• Titrimetric karl fischer method .
Loss on drying: To determine LOD , place 2-5g of
the prepared air dried crude drug. The
substance is to be dried to constant mass by
heating in an oven at 100 .
19. Viscosity:
• Viscosity of a liquid is constant at a given
temperature and is an index of its
composition.
• Hence, it is used as a means of standardising
liquid drugs.
• Example:
Liquid paraffin – less than 64 centistokes.
20. Melting Point:
• It is one of the parameters to judge the purity
of crude drugs containing lipids as
constituents.
• They may of animal or plant origin and contain
fixed oils, fats and waxes.
• The purity of the following crude drugs can be
ascertained by determining their melting
points in the range shown against each of
them
• Example: Coca butter (30⁰ - 33⁰C)
21. Ash Content:
Determination of total ash
Determination of acid-insoluble ash
Determination of water soluble ash
1. place about 2-4g of air dried material . Heat it at
500 .cool in a desicator and weigh. To it add 2ml
of water and heat it on the water bath allow the
residue to cool in a desicator for 30 mins
calculate the content of total ash in mg per g of
air –dried material.
Ex : amla –not more than 5%
opium – not more than 6%
22. Extractive values:
• In crude drugs, sometimes the active chemical
constitutes cannot be determined by normal
procedures.
• In such cases, water, alcohol or ether soluble
extractive values are determined for
evaluation of such drugs.
• Example: Water soluble extracts like Aloe vera
Alcohol soluble like Ginger
23. IV. Chemical Evaluation :
chemical tests are carried out using various
chemical reagents to identify the nature and
quality of chemical constituents of crude drugs.
chemical tests may be qualitative or quantitative .
Various qualitative chemical tests :
i. Carbohydrates – molisch test
ii. Proteins – biuret test
iii. Alkaloids – mayers test
iv. Tannins – gelatin test
24. Instrumental methods:
• They make use of various instruments for
evaluation like colorimetry, flourimetry
spectrophotometry etc.
Chemical constants tests:
• These are like acid value, iodine value and
ester value etc are used for the identification
of fixed oils and fats.
25. Individual chemical tests:
• These are the tests which are used for
identifying particular drugs.
• Examples: Halpher’s test for cotton seed oil.
Microchemical tests:
• These are the tests which are carried on
slides.
• Example: Euginol in clove oil is precipitated as
potassium euginate crystals.
26. V. Biological Evaluation( pre clinical studies) : It
is employed when the drug cannot be
evaluated satisfactorily by chemical and
physical methods.
a) Determination of bitterness value
b) Determination of haemolytic activity
c) Determination of swelling index
d) Determination of foaming index
27. Determination of swelling index:
Take 1g of isapgol seeds in a measuring
cylinder and add 25 ml of water and allow it
to stand for 24 hrs and measure the
difference of intial height and the height
after 24hrs . The difference in the heigt gives
the swelling factor of isapgol seeds .
28. 6.Toxicological evaluation:
a) Determination of arsenic and heavy metals
b) Determination of pesticide residues
c) Determination of micobial contaminants
d) Radioactive contamination
Few examples and limits are
Arsenic: max 1.0 ppm
Lead : max 10.0 ppm
Cadmium : max 0.3 ppm
