This document discusses different methods for evaluating crude drugs, including their identity, quality, and purity. It describes five main evaluation methods: morphological, physical, chemical, biological, and microscopic. Morphological evaluation examines characteristics like color, odor, taste, and shape. Physical evaluation includes tests of solubility, moisture content, viscosity, melting point, and ash value. Chemical evaluation isolates and identifies active constituents. Biological evaluation examines a drug's effects on living systems. Microscopic evaluation allows detailed study of cellular structures under magnification. Together, these methods provide a comprehensive quality assessment of crude drugs.

1. Quality Control of Drugs of
Natural Origin
(Part-2)
Presented by-
Diksha Kataria
Asst. Prof.
LSCP, Sirsa

2. Evaluation of Crude Drugs
Evaluation of crude drugs means conforming its identity, determining its quality and
purity and detection of nature of adulteration.
Identity: Identification of biological source of the drug.
Quality: The quantity of the active constituents present.
Purity: The extent of foreign organic material present in a crude drug.
Quality of the drug is directly proportional to the purity of the drug.

3. Evaluation is necessary because of three main reasons:
a) Biochemical variation in the drug
b) Deterioration due to treatment and storage
c) Substitution and adulteration
There are five methods of drug evaluation-
1. Morphological or Organoleptic Evaluation
2. Physical Evaluation
3. Chemical Evaluation
4. Biological Evaluation
5. Microscopic Evaluation

4. Morphological Evaluation
It is a technique of qualitative evaluation of drugs by means of morphological and sensory profiles of
drugs.
It refers to evaluation of drugs by colour, odour, taste, touch, shape size and special features like touch,
texture etc.
There are four kinds of morphological characters:
a) Shape, size and external color
b) External markings
c) Fracture and internal colour
d) Odour and taste
Example-
Pungent taste of ginger, brown color of cinnamon, sweet taste of liquorice, aromatic odour of fennel,
globular shape of amla etc.

5. Physical Evaluation
Typical physical constants are sometimes taken into consideration to evaluate the drug.
Physical constants such as elasticity in fibres, viscosity of drugs containing gums, swelling factor for
mucilage containing materials, froth content of saponin drugs, moisture content, melting and boiling points
are some important parameters used in the evaluation of drugs.
Ultraviolet light is also used for determining the fluorescence of extracts of some drugs.
Some of the physical constants employed are:
 Solubility: It is defined as the amount of solvent required to dissolve 1g of drug. The presence of
adulterant in a drug can also be identified by solubility studies. For example, Castor oil is soluble only in
3 volumes of 90% alcohol, while the adulterated form shows better solubility in alcohol.

6.  Moisture content: It is represented by loss on drying. The moisture content of a drug should be
controlled in order to prevent its decomposition. This is determined by heating a drug at 105˚C in
an oven to a constant weight.
 Viscosity: Viscosity of a liquid is constant at a given temperature and is an index of its
composition. For example, Liquid paraffin – not less than 64 centistokes at 37.8˚C.
 Melting point: It is a parameter to judge the purity of the drug. In case of pure chemicals, the
melting points are sharp and constant. For example,
S.No. Drugs Melting Point(˚C)
1. Colophony 75-85
2. Cocoa butter 30-33
3. Bees wax 62-65

7. Refractive index: When a ray of light of different density passes from one
medium to another medium, it is bent from its original path. Thus, the ratio of
velocity of light in vacuum to its velocity in the substance is said to be the
Refractive index of the second medium. It is measured by using a
refractometer.
Ash value: The residue remaining after incineration of a known quantity of the
air dried crude drug, is known as the ash content of the drug. Ash simply
represents the inorganic salts naturally occurring in drug or adhering to it or
deliberately added to it as a form of adulteration.
Extractive value: In crude drugs, sometimes the active chemical constituents
cannot be determined by normal procedures. In such cases, water, alcohol or
ether soluble extractive values are determined for evaluation of such drugs.

8. Chemical Evaluation
 It comprises of chemical tests and assays.
 The isolation, purification and identification of active constituents are chemical
methods of evaluation.
 The purity of crude drug is ascertained by quantitative estimation of active chemical
constituents present in them.
 The method maybe useful in determining single active constituent or group of related
constituents present in the same drug.
 Qualitative chemical tests are useful in detection of adulteration.

9. Biological Evaluation
Some drugs have specific biological or pharmacological activity which is utilized
for their evaluation. Experiments can be done both on intact or isolated organs of
animals. In this method, the response produced by the test drug on a living
system is compared with that of the standard preparation. This process is known
as bioassay.
Bioassay methods are mainly of 3 types:
i. Toxic- animals are used
ii. Symptomatic- animals are used
iii. Tissue- isolated organs or tissues are used

10. Some of the important biological evaluation are following:
a) Mice are used to test the Rabies and Diphtheria vaccine
b) Domestic chickens are used to test the oxytocin injection
c) Pigeons are utilized to test the cardiotonic activity of Digitalis
d) Rabbits are employed to test the muscle relaxant activity of curane alkaloids.
e) Some bacteria such as Salmonella typhi and Staphylococcus aureus are
employed to determine the antiseptic value
f) Finally the drugs are tested on human beings, before introducing it in the
market.

11. Microscopic Evaluation
This method of evaluation allows more detailed study of drugs
It is mostly used for qualitative examination of organized crude drugs in
powdered or entire form
Microscope is used for this purpose which magnifies the image of a
minute structure into an enlarged form
Various reagents or stains are used to differentiate the cellular structures.
The characteristics of cell wall, cell contents, fibres, vessels etc. can be
studied in detail
Also, the other parameters such as stomatal number, palisade ratio, vein
islet number, length of fibres etc. can be studied