The confirmation of its identity, determination of its quality and purity and detection of the nature of adulteration present is known as evaluation of crude drugs. Identity means to determine the authenticity, or exact biological source of drug. Purity means to check the presence of foreign material, either organic or inorganic which may be present in the drug accidentally or intentionally added to the drug to earn more money. This is a readymade notes one can prepare themselves for examination. Reasons for the evaluation of Crude drug: 1. Biochemical variation in the drug, 2. Deterioration due to treatment and storage, 3. Substitution and adulteration, as a result of carelessness, ignorance or fraud.

1. Evaluation of Crude Drugs
Prepared by: Miss Pranita Sunar
Assistant Professor
Deptt. of Pharmacognosy
Mata Gujri College of Pharmacy, Kishanganj.
For D. Pharm & B. Pharm.

2.  The confirmation of its identity, determination of its quality and purity and detection of nature of
adulteration present is known as evaluation of crude drug.
 Identity means to determine the authenticity, or exact biological source of drug. Whether the drug we
are using are from same biological source or from different source.
 Quality means to determine the concentration of therapeutically active constituent present in the drug
and comparison with the standard value so that the drug produces desirable therapeutic effect.
 Purity means to check the presence of foreign material, either organic or inorganic which may be
present in the drug accidently or intentionally added to the drug to earn more money.
 Reasons for the evaluation of Crude drug:
1. Biochemical variation in the drug,
2. Deterioration due to treatment and storage,
3. Substitution and adulteration, as a result of carelessness, ignorance or fraud.

3. Methods of Evaluation of Crude drug
 There are different methods by which the crude drugs can be evaluated.
Sl.
No.
Evaluation method
Description
1. Morphological /Organoleptic
Evaluation
Drugs are evaluated with the help of sense
organs.
Example: colour, taste, texture etc.
2.
Microscopic Evaluation
Drug or its powder is examined under the
microscope to study the arrangement of tissue
and characteristics of powder.
3.
Physical Evaluation
Evaluation of Physical standards or constants
such as moisture content, ash content,
extractive value etc.
4.
Chemical Evaluation Determination of active constituent in a drug
by the chemical tests.
5.
Biological Evaluation Determination of Biological activity of drug.

4. I. Organoleptic Evaluation
Organoleptic evaluation is the simplest form of evaluation in which the study of drugs is done
using organs of senses. It includes characters like colour, odour, taste, size, shape, special
features like touch, texture etc of crude drug. Morphological and organoleptic features of
various parts of plants are very useful in identification of crude drug and also give an idea about
the presence of adulterants in crude drug.
 Examples
a. Wavy shape- Rauwolfia, Disc shape- Nuxvomica,
b. Strength of odour like musty, moldy, rancid, fruity,
c. Aromatic odour of umbelliferous fruit.
d. Sweet taste of honey and liquorice.
e. Bitter taste of gentian and chirata.
f. Brown colour of cinnamon.
g. Pungent taste of capsicum and ginger.
h. Mucilaginous taste of Ispaghula.
i. Fractured surface: Cinchona, cascara bark, quasia wood.

5. II. Microscopic Evaluation
Microscopic evaluation is essential in the initial identification of herbs, as well as in identifying small
fragments of crude drug or powdered herbs, and in detection of adulterants (e.g. animal faeces mold, fungi
etc.) as well as identifying the plant by characteristic tissue features.
 It involves the detailed examination of organized drugs in entire or its powder under the microscope to
study the arrangement of tissue (histological characters).
 The Longitudinal Section (L.S) & Transverse Section (T.S) of organized crude drug are studied under
the microscope with the help of staining agent. Special attention is given to the type of tissues, their
arrangement, presence or absence of special substances like calcium oxalate crystals, starch grains,
size and shape of starch grains, cell contents etc.
 Example:
Nux vomica have lignified trichomes, Fennel contains vascular bundles which are surrounded by
reticulated parenchyma and shows the presence of vittae (oil gland) which secrete volatile oil.
Microscopic evaluation also includes the study of constituents by application of chemicals to small
quantities of drugs in powdered form or to histological sections of the drug known as microchemistry or
chemomicroscopy. Example
a. A drop of phloroglucinol and conc. HCl give red stain with lignin.
b. Mucilage stains pink with Ruthenium red.

6.  Parameters of Microscopic evaluation
Leaf constant or diagnostic characters of Leaves
 1.a) Palisade ratio 1.c) stomatal number
 1.b) vein islet number 1.d) stomatal index
 1.e) veinlet termination number
III. Physical Evaluation
Following are the methods of physical evaluation:
a. Determination of moisture content
b. Determination of viscosity
c. Determination of melting point
d. Determination of ash content
e. Determination of Extractive
f. Determination of volatile oil content.

7. IV. Chemical Evaluation
 This method consists of isolation, purification and identification of the active chemical constituent from
the crude drug and consists of the various tests like acid value, saponification value, iodine value, ester
value, acetyl value and determination of methoxy group etc. Chemical evaluation is also helpful for
identification of crude drug.
 Example: Van urk’s test for Ergot, Halphenes test for arachis oil, Borntrager’ test for anthraquinone
glycoside. Ex. Starch gives blue colour with Iodine.
V. Biological Evaluation OR Bioassay
 Bioassay means the measurement of the sample drugs, which produce the same biological effect as that
of standard preparation.
 It is performed for those drugs which cannot be tested properly in the laboratories. They are performed
on cells, bacteria, fungi, animals etc. This method is used for antibiotics, vitamins, hormones and cardiac
glycosides.

8. NOTE: The moisture content determination, extractive value and ash value has been
uploaded separately.
Thank You.