What is evaluation of drug?
 Evaluation of drug means confirmation & comply of drug.
 The aim of the drug evaluation is to identify and determine the
quality and purity of the crude drug and detecting the nature of
adulteration.
 The evaluation of crude drug is essential because-There may be biochemical variations in the drug
-There may be deterioration due to storage
-Substitution and adulteration may be present as a
result of carelessness, ignorance etc
Evaluation includes:
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estimation of active constituent present in the crude drug
its morphological & microscopic analysis
physical evaluation of crude drug
the biological behavior of crude drug extracts
determination of pharmacological action.
Methods of crude drugs evaluation
The crude drugs can be identified on the basis of their
morphological, histological, and chemical characters. The
different techniques involved in standardization of crude drugs
are-
i) Morphological and organoleptic evaluation
ii) Microscopic evaluation
iii) Physical evaluation
iv) Chemical evaluation
v) Biological evaluation
Morphological and organoleptic evaluation
It refers to the evaluation of drugs by color, odor, taste, size, shape
and special features like texture.
 The general appearance of the lot of a crude drug indicates
whether its likely to comply with standard. e.g. fractured surface in
cinchona & cascara are important characteristics .
 Aromatic odour of fruit & sweet taste of liquorice are important in
evaluation
 Disc –shaped structure of nux-vomica ,conical shape of aconite are
important in diagnosis .
 The wave shape of rauwolfia & ginger ,brown colour of cinnamon ,
odour & taste of spice drug like black pepper ,nut meg ,caraway etc
are also important diagnostic organoleptic characteristics.
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Microscopic evaluation
 This method allows more detailed examination of a
drug and their identification by their known histological
characters.
 Microscope by the virtue of its property to magnify,
permits minute sections under study to enlarge so
that, leaf constants, stomatal index, palisade ratio can
be determined.
 Various reagents & stains can be used to distinguish
cellular structure.
 This evaluation also covers study of the constituents
by application of chemical method to small quantities
of powdered drug (called chemo microscopy).
Physical evaluation
In this evaluation, physical standards are to be determined for drugs
which is rarely constant for crude drugs but may help in evaluation.
These are :
 Moisture content- is determined by heating a drug at 1050C in the
oven to constant weight.
 Viscosity of liquid - is constant at a given temperature & is an index
of composition
 Melting point - it is one of the parameters to judge the purity of
crude drugs .
 Solubility- the presence of adulterant in a drug could be indicated by
solubility. e.g. the glycosides are extract with alcohol &water while
aglycone are soluble in non polar solvent like benzene.
 Optical rotation - is determined at 250C using sodium lamp as the
source of light .plane of polarized light may be rotated towards right
(dextrorotatory ) or towards left (levorotatory) .
Physical evaluation……
 Refractive index - is the ratio of the velocity of light in vacuum to its
velocity in the substance .It s constant for purity drugs at constant
temperature.
 Ash values - ash which is simply represents inorganic salts ,
naturally occurring in drug or adhering to it as a form of adulteration
like sand , oil , calcium oxalate ,chalk powder.
 Extractives -various solvents are used for determination of
extractives , the solvent used for extraction is in a position to
dissolve appreciable quantities of substance
 Volatile oil content ,aromatic drugs is due to their odorous i.e.
volatile oil content e.g caraway ,dill ,clove , cardamom seed .
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 Foreign organic matter ;the limit for foreign organic matter is
mentioned for natural drugs of vegetable origin
Chemical evaluation
 It consist of different chemical tests& chemical assay .The isolation,
purification & identification of active constituents are chemical
methods of evaluation.
 Quantitative chemical test like acid value, saponification value ,
sulphated ash, ester value ,acetyl value are useful in evaluation
resins,balsams &volatile oil etc.
 Qualitative chemical tests are useful in detection of adulteration
,these specific test like balsams &waxes is detected by copper
acetate murexide test for purine bases etc,
 The purity of crude drugs is detect by quantitative estimation of
active constituents present in drugs for example titrimetric estimation
to estimate of alkaloid in crude drugs ,ester& aldehyde content of
volatile oils etc
 The method may be useful in determining single active constituent
or the group of related constituents present in the same drug.
Biological evaluation
When the estimation of potency of crude drug or its
preparations are done by means of measuring its effect on
living organisms like bacteria, fungal growth, or animal
tissue, it is known as biological effect of the drug, compared
to the standard drug.
By these methods a crude drug can be assessed and further
clinical trial can be recommended. It is known also as
bioassay.
Biological evaluation…
The activity is represented in units known international unit
(I.U). i:e the specific biological activity contained in each I.U
e.g Digitalis contained 76mg of standard preparation in
one I.U.
Bioassay methods are mainly three type:
a-toxic
b-symptomatic &
c-tissue methods.
- In toxic & symptomatic- the animals are used
- In tissue method- isolated organ or tissue is used