1. Drug evaluation may be defined as the determination of identity,
purity and quality of a crude drug.
Identity – identification of biological source of the drug.
Quality – the quantity of the active constituents
present.
To maintain quality of the crude drugs, it is necessary to;
Select proper source of crude drugs (either wild or cultivated)
Collect the crude drugs at appropriate time
Collect the required parts of the plants
Preparation of collected drugs by proper cleaning and drying
Properly preserve the crude drugs in order to avoid contamination due to
microbes and against moisture, heat, air and light.
Purity – the extent of foreign organic material present
in a crude drug.
CRUDE DRUG EVALUATION
2. • Importance of evaluation of crude drugs:
Determination of Biochemical variation in the
drugs
Identification of deterioration due treatment
and storage
Substitution and adulteration, as result of
carelessness, ignorance and fraud
4. 1. Organoleptic (Morphological) Evaluation
• This refers to drug evaluation by means of organs of sense
and includes other sensory organs like color, odour, taste, size ,
shape and texture
• It includes the study of morphology and other sensory
characters.
• It also includes the visual examination of crude drugs using
lens or dissection microscope
6. Shape and size
Flowers:
Floral parts: stigmas, corollas, anther, ovary, receptacle.
Saffron extracted from the flowers which is used as an essence in the food.
Leaves and leaflets: Length, width, apex, margin, base, venation, the texture of the leaf and the
hairs in upper and lower surface. The feel of the surface described as soft, hairy smooth.
7. Bark: The barks occur in three shapes:
Flat or curved pieces.
Single quill.
Double quills.
Barks have two surfaces, an outer and inner. iii- The inner surface is usually
lighter in color than the outer surface
8. Seeds :
Seeds are developed form the ovules in the carpel of the flowers. They are
characterized by the hilum, micropyle etc.
9. Odor of crude drugs
The crude drugs may be odorless or pose an odor which may be;
• Distinct
• Indistinct
General terms for describing odor are;
Aromatic
Balsamic
Alliaceous
Fishy
Spicy
Fruity
Pungent etc…
10. Taste of crude drugs:
• The crude drugs may posses a characteristic taste or may be
tasteless.
General terms used in describing taste are:
Acid (sour)
Saccharine ( sweet)
Saline (salty)
Alkaline
Bitter
Tasteless
12. • Fractures and internal color:
Fractures and internal color of crude drugs refer
to the external markings that are characteristics
of a particular drug and color after breaking the
crude drug.
e.g. Liquorice- Fibrous fracture
Aconite- Horny fracture
Internal color of a crude drug is usually lighter
compared to the external colour.
e.g.. Turmeric, ginger
13. MicroscopicalEvaluation
Microscopy is useful for the study of the internal structure,
constitution, and inclusions of plant and animal cells or other
objects in detail.
It is necessary for the detection of adulterants and contaminants
of the herbal preparations and thus provides means for assessing
the authenticity and quality of herbal drugs.
Size, shape, relative position of different cells and tissues as
well as the chemical nature of the cell walls, and the form and
nature of cell contents are considered during microscopic analysis
14. 1. By cutting thin sections of various parts of drug
Identification of crude drug using qualitative microscopy:
Every plant possess a characteristic tissue structure that can be demonstrated through
study of;
Tissue arrangement
Cell walls structure
Cell contents (calcium oxalate crystals, fibers, parenchyma etc.)
Reagents
Lignin stains red or pink with a drop of phloroglucinol and concentrated hydrochloric
acid;
Mucilage are stained pink with ruthenium red;
Starches stained blue with iodine solutions
15. 1. By cutting thin sections of various parts of drug
Identification of crude drug using qualitative microscopy:
16. Microscopic linear measurements:
These include identification of crude drug by measurements like;
Size of starch grains
(e.g. diameter of starch grain in cassia bark distinguishes from
cinnamon)
Size of the stomata
Diameter of phloem fibers (e.g. detection of cassia in cinnamon)
Width of the vessel (e.g. detection of clove stalks in powdered
cloves)
Length and width of fibres
17. • Determination of leaf constants:
• Stomatal Number: The average number of stomata present per square millimeter of
the epidermis is known as stomatal number. Stomatal number is relatively constant for
a particular species of same age and hence, it is taken into consideration as a diagnostic
character for identification of a leaf drug. Example: Datura– 141 (upper epidermis)
Stomatal index:
• It is the percentage which the numbers of stomata form to the total number of
epidermal cells (each stomata being counted as one cell).
S.I= S/E+S *100
• Here; S = Number of stomata per unit area E = Number of epidermal cells in the same
unit area.
Example:Datura
18. • Vein-islet number:
It is defined as the number of vein islets per square mm of leaf surface
midway between the midrib and the margin. This value is constant for a
given specie of a plant and used as a characteristic for the identification of
allied specie.
Vein let termination number:
• It is defined as the number of veinlet termination per square mm of leaf
surface midway between the midrib and the margin
crude drug Vein islet number Vein termination
Senna 19.5-22.5 24.2-31.4
Digitalis 2-5.5 2.5-4.3
19. Palisade ratio:
Palisade ratio is defined as the average number of palisade cell
beneath each epidermal cell of leaf.
Species Palisade ratio
Atropa belladona 6-11
Digitalis purpurea 3.7-4.2
20. Physical evaluation of crude drugs
• Moisture Content
• Specific Gravity
• Density
• Optic Rotation
• Refractive Index
• Melting Point
• Viscosity
• Foreign Organic Matter
• Ash Value
• Extractive Value
21. Moisture content
• Moisture content is responsible for
the decomposition of crude drug due
to chemical change or microbial
attack.
• It is necessary to determine and
control the moisture content of
crude drug .
• It is determined by heating the drug
at 105°C in an oven to a constant
weight.
• Moisture content of Digitalis is 5%
w/w.
22. Viscosity
• Resistance of the fluid to flow .
• Viscosity of a liquid is constant at given
temperature . Hence it is used as a means of
standardizing liquid drugs.
• LIQUID PARAFFIN kinematic viscosity is 64
centistokes at 37.8 °C.
23. Melting point
• It is one of the parameter to judge
the purity of crude drug.
• In case of pure chemical or
phytochemicals , melting point are
very sharp and constant . Since the
crude drug from animals and plants
origin contain the mixed chemicals .
• Purity of crude drug can be
determined by their melting points.
• COLOPHONY 75-85°C
24. UV Light
• Certain drugs fluoresce when the cut surface or
the powder is exposed to ultraviolet radiation ,
And it is useful in the identification of those drugs
• Indian and Chinese Rhubarb are very difficult to
distinguish and is very difficult form , but
examination in ultraviolet light gives such marked
differences in florescence that the varieties can
be easily distinguish from each other .
25. Solubility
• The number of ml of solvent required to
dissolve 1g of drug .
• The presence of adulteration in a drug could
be indicated by solubility studies.
• Balsam of peru is soluble in chloral hydrate
solution.
• Colophony is freely soluble in light petroleum.
Asafoetida is soluble in carbon disulphide.
Alkaloidal bases are soluble in chloroform.
26. Specific gravity
• It is also referred to as “RELATIVE DENSITY’’
• It is the ratio of the mass of a liquid or solid to
the mass of an equal volume of distilled water
at 4°C.
• Its measure gives the idea of the floatability
of drug. If specific gravity is greater than 1 the
substance sinks. If specific gravity is less than 1
the substance floats. Cotton seed oil 0.88-0.93
• Coconut oil 0.925 Castor oil 0.95
27. Melting point
• Melting point of a solid is the
temperature at which it changes
states from solid to liquid
• Crude drugs contains number of
chemicals, therefore their M.P is
not sharp but it is in range
• Bee wax 62-65 °C
Wool fat 34-44 °C
Agar melts at 85 °C
28. Refractive index
• When a ray of light passes from one medium to
another medium of different density, it is bent from its
original path. Thus, the ratio of velocity of light in
vaccum to its velocity in the substance is said to the
Refractive index of the second medium.
• It is measured by means of refractometer.
• R1 of a compound varies with the wavelength of the
incident light, temperature and pressure.
• Castor oil – 1.4758-1.527
• Clove oil- 1.527-1.535
29. Optical rotation
• Certain drugs can rotate plan
of polarized light to right
(dextrorotatory) or to the left
( Laevorotatory)
• Polarimeter
• It is determined by using
sodium vapor lamp at 25 °C
30. Foreign organic matter
• The parts of the organ or organs other than
those parts of drugs mentioned in the
definition and description of the drug are
known as Foreign organic matter
• Insect, moulds, earthy matters, animal excreta
etc
• Garlic not ore than 2%
• Saffron not more than 2%
31. Ash value
• The residue remaining after
incineration is the ash content of
the drug (inorganic salts of
carbonates , phosphates ,
silicates of sodium , potassium,
calcium and magnesium ) is
known as ash content.
• Ash value is the criterion to judge
the identity and purity of crude
drug.
• Useful for detecting low grade
products, exhausted drug and
drugs from earthy matter .
32. Types of ash value
• Total ash value
• Acid insoluble ash value
• Sulphated ash value
• Water soluble ash value
33. Total ash
• It is used for detecting crude drug that are
mixed with minerals like sand , soil , calcium
oxalate chalk powder or drugs with different
organic contents to improve appearance .
• Example GINGER 6% w/w
• Temperature should be less than 450◦ C
because at high temp. alkali chlorides maybe
lost
34. Acid insoluble ash
• Means total ash insoluble in dilute hydrochloric
acid
• It is used for the determination of earthy matter
present on roots , rhizomes and also on leaves .
• It is useful for drugs in which soil contamination is
very common Crude drug contains calcium
oxalate crystals , the amount may varies
depending on the environmental conditions.
• Cannabis – not more than 5%
35. Water soluble ash
• It is used to detect the presence of material
exhausted by water.
• tea leaves, Ginger
36. Extractive value
• The extract obtained by exhausting crude drugs with
different solvents are approximate measures of their
chemical constituents . Various solvents are used
according to the type of the constituents to be analyzed .
• SIGNIFICANCE
• Useful for the evaluation especially when the
constituents of the drugs can not be readily estimated by
any other means .
• Helps to identify the nature of chemical constituents
• Identification of adulterants
37. Types of extractive value
• Water soluble extractive value
• Alcohol soluble extractive value
• Ether soluble extractive value
38. 1. Water soluble extractive value is applied for the drugs
which contain water soluble constituents such as
tannins, sugars, plant acids and mucilage.
Aloe not less than 25%
2. Alcohol soluble extractive value is applied for the drugs
which contain alcohol soluble constituents such as
tannins, resins and alkaloids . Asafoetida not less than
50%
3. Ether soluble extractive value is applied for the extraction
of volatile oils, fixed oils and resins.
Linseed not less than 25%
Capsicum not less than 12%
39. Chemical evaluation
• Determination of the active constituent in a
drug by chemical tests is referred to as
chemical evaluation. Isolation, purification
and identification of chemical constituents
40. • QUALITATIVE CHEMICAL TEST
• QUANTITATIVE CHEMICAL TESTS
• CHEMICAL ASSAYS
• INSTRUMENTAL ANALYSIS
41. QUALITATIVE CHEMICAL TEST
• It includes the identification of various phytoconstituents
• Extract obtained using petroleum ether, chloroform,
ethanol and water was prepared using the respective
solvent.
• These extracts along with positive and negative controls
were tested for the presence of active phytochemicals viz:
tannins, alkaloids, phytosterols, triterpenoids, falvonoids,
cardiac glycosides, anthroquinone glycosides, saponins,
carbohydrates, proteins, amino acids and fixed oils & fats
following standard methods
42. Tannins : Ferric chloride Test: Added a few drops
of 5% ferric chloride solution to 2 ml of the test
solution. Formation of blue color indicated the
presence of hydrolysable tannins.
Alkaloids: Dragendorff’s Test:
Phytosterols : Liebermann-Burchard’s Test
Micro chemical tests:
These are the tests which are carried on slides.
Example: Eugenol in clove oil is precipitated as
potassium euginate crystals.
43. Quantitative chemical test
• Acid value ( resins, balsams)
• Saponification value ( balsams)
• Ester value (balsams, volatile oils)
• Acetyl value ( volatile oils)
44. Chemical assays
• Chemical assays include assay for alkaloid,
resin, volatile oil, glycosides, vitamins, or
other constituents (gravimetric or colorimetric
or titrimetric )
• Total alkaloid content in belladonna herb
• Alkaloid strychnine in nuxvomica
• Resin in jalap
• Vitamin in cod-liver oil
47. Spectrophptometric methods
There are several instruments that are used to perform spectroscopic
analysis.
spectroscopy requires an energy source and a device for measuring
the change in the energy source after it has interacted with the
sample (spectrophotometer)
Electromagnetic radiation: electromagnetic waves
The EM spectrum is generally divided into seven regions, in order of
decreasing wavelength and increasing energy and frequency. The
common designations are: radio waves, microwaves, infrared (IR),
visible light, ultraviolet (UV), X-rays and gamma rays.
Wavelength of light absorbed tells the nature of the compound while
the intensity of absorbed light tells the concentration.
51. Infra Red spectroscopy
IR spectroscopy is concerned with the study of absorption of infrared
radiation, which causes vibrational transition in the molecule. Hence, IR
spectroscopy also known as Vibrational spectroscopy.
Most of the analytical applications are confined to the middle IR region
because absorption of organic molecules are high in this region.
Different functional groups absorb characteristic frequencies of IR radiation
Hence gives the characteristic peak value.
52. Applications:
Identification of functional group and structure elucidation
Infra red spectroscopy is used to establish the structure of an unknown compound.
Infra red spectroscopy is also useful in the detection of the impurity in a compound by
comparing its spectrum with the spectrum of the authentic sample of the compound.
A pure sample always consists of sharp peaks and bands while the impure sample will
have poor bands with some additional bands.
53. Nuclear magnetic resonance spectroscopy
Nuclear Magnetic Resonance (NMR) is a spectroscopy technique which is
based on the absorption of electromagnetic radiation in the radio
frequency region 4 to 900 MHz by nuclei of the atoms.
54. • Proton NMR –Proton Nuclear magnetic resonance spectroscopy is one of
the most powerful tools for elucidating the number of hydrogen or proton
in the compound
C 13 NMR- carbon Skelton of the compound
55.
56. Mass spectroscopy
• Organic molecules are bombarded with electron
converted into Highly energetic positively charged
ions (Molecular ions or Parent ions)
• Further break up into smaller ions (Fragment ions or
Daughter ions)
• The formed ions are separated by Deflection in
Magnetic field according to their Mass and Charge
57. Mass spectroscopy
• Mass spectrometry is an instrumental technique in
which sample is converted to rapidly moving positive
ions by electron bombardment and charged particles
are separated according to their masses.
• Determination of molecular weight of compounds
• mass spectroscopy along with chromatography is the
most effective method for identification of
phytoconstituents
58.
59. BIOLOGICAL EVALUATION
• The plant or extract can be evaluated by various
biological methods to determine the
pharmacological activity, potency, and toxicity.
• The biological evaluation would serve better than the
physical and chemical evaluation for drugs could not
be satisfactorily assayed by these methods.
• Conclude biological activity of crude drug
60. • The assays are conducted by determine the
amount of drug of known potency required to
produce a definite effect on suitable test
animals or organs under standard conditions
reference std are used to minimize the error.
• Toxicity studies are determined in suitable
animal model to decide the lethal dose and
effective dose of crude drugs.
61. • Microbial assay
Determine the effect of drugs in various
microorganism. helps in the identification of
antimicrobial drugs
