WHO & ICH GUIDELINES FOR ASSESSMENT OF HERBAL DRUGS (PART - 3)
PHYSICAL EVALUATION OF CRUDE DRUGS
PHYSICAL EVALUATION OF CRUDE DRUGS:-
Physical method of
evaluation is determined wherever possible these are rarely
constant for
crude drugs. But may help in evaluation.
PARAMETERS:-
1. Foreign organic matter
2. Moisture content
3. Ash value
4.
Extractive value
5. Swelling factor
6. Viscosity
7. Melting point
8. Solubility
9. Optical rotation
10. Refractive
index
11. Volatile oil content.
1.FOREIGN ORGANIC
MATTER:-
The parts of the
organs or organs other than those named in the definition and
description
of the drugs. these may include insects, moulds, earthy
material etc.
Medicinal plant
material should be entirely free from them which is difficult so
pharmacopeias provide the limit for the
presence of other parts of the
plants. Each crude
drugs has its own limits for presence of FOM.
E.g. Garlic and saffron should not
contain more than 2 %.
2.
Moisture content:-
An excess amount of water in medicinal
plants material encourage microbial growth and
the presence of fungi and
insects cause deterioration. Moisture content of crude drug
responsible for
decomposition of crude drug due to chemical change or microbial attack.
Hence
it is necessary to determine and control the moisture content of crude drugs.
Some important physical and chemical
methods used to determine the
moisture content in drugs are…..
A.
Loss on drying
B. Karl Fischer
method (chemical method).
C.
Azeotropic distillation method
D.
Spectroscopic method.
A] LOSS ON DRYING:-
Loss in the weight of
the sample is mainly due to the presence of water but also due to
the
presence of small amount of volatile material contribute
to the weight loss LOD is
determined by heating a drug at 105. c
in an oven to a constant weight and
calculate the loss
of weight.
E.g. Digitalis – Not more than 5%w/w
Ergot – NMT 8%w/w.
B] KARL FISCHER METHOD:-
This
is chemical method extensively used for the determination of
very small amount of
moisture.
E.g. The crude
drugs like Digitalis, Ipecacuhna.
The
powdered material is exhausted of water with anhydrous solvents
like Dioxan and
aliquot is taken for titration. The
karl Fischer reagent
contain solution So2 and pyridine in
dry methanol.
Iodine is reduced by So2 in the presence of water causing
loss dark brown
color of the reagent.
C] AZEOTROPIC DISTILLATION METHOD:-
Water forms a
heterogeneous azeotrope with the solvents
like toluene, benzene and
xylene
such types of binary mixtures can be distilled up to the
azeotropic composition. Dean stark
apparatus
is used for the determination of moisture content,. Organic
solvent forms a
azeotropic mixture with water Present in the crude
drug. When the drug is
heated the
organic solvent and water is distilled Together which is
collected in a graduated tube of the
apparatus.Water forms a bottom
layer being heavier which can be directly
read after complete
distillation.
D] SPECTROSCOPIC METHOD:-
Water will absorb
energy at various wavelengths in electromagnetic Spectrum, this factor is
considered as the quantitative determination of
moisture, which is done by IR and UV
spectroscopic
methods. . This method ideal for
substances that contain very less quantity of
water.
3. ASH VALUE:- :-
The residue remaining after incineration is called ash (Ash is a inorganic salts of carbonates,
phosphates, Silicates, of sodium, potassium, calcium and magnesium)
- Physiological ash:- The ash derived from the plant tissue itself .
- Non Physiological ash:- The residue of extraneous matter adhering to the plant
surface (sand, oil, etc).
Ash value is used to determine quality & purity of a crude drugs. The maximum temperature
used for total ash is not more than 4500c.
TYPES OF ASH VALUES:
A] TOTAL ASH VALUE:-
It is used for detecting low grade products, exhausted drugs, & excess of sandy & earthy
materials.
Procedure:-
Accurately weighed 2 gm of the powdered drug was taken in a tarred silica dish and it was
incinerated at a temperature not exceeding 450°C until free from carbon. The sample was
cooled and weighed. The percentage of ash was calculated with reference to the air dried
drug.
B] ACID INSOLUBLE ASH VALUE:-
Used for the determination of earthy matter present on roots, rhizomes, & also on the leaves.
Procedure:-
The ash obtained described as total ash was boiled for 5 min. with 25 ml of dilute
hydrochloric acid. The insoluble matter was collected on an ash-less filter paper and washed
with hot water and ignited to constant weight. The percentage of acid insoluble ash was
calculated with reference to the air dried drug.
The majority of crude drugs contain calcium oxalate whose quantity varies frequently.
Therefore Total ash of a crude drugs vary within wide limits for specimen of genuine drug.
E.g. for Rhubarb, Total ash ranges from 8-40% and in these case determination of acid
insoluble content is more preferable.
C] WATER SOLUBLE ASH VALUE:-
Used to detect either material exhausted by water or not.
E.g. Tea leaves, Ginger rhizomes etc.
Procedure:-
To the ash obtained as total ash 25 ml water was added and boiled for 5 minutes. The
insoluble matter was collected on an ash less filter paper, washed with hot water and ignited
in a crucible for 15 minutes at a temperature not exceeding 450оC. The weight of this
residue was subtracted from the weight of total ash. The content of water-soluble ash with
reference to dried drug was calculated.
D] SULPHATED ASH:-
Used for the detection of low grade products. This ash is produced after treating the drug
with sulphuric acid to get sulphate salts. Temp- more than 6000c.
4. Extractive values:-
It gives an idea about the nature of the chemical constituents present in a crude drug.
Useful for estimation of constituents extracted with the solvent used for extraction.
Employed for material for which as yet no suitable chemical or biological assay exists.
It can be done by following methods: Cold maceration, hot extraction and ethanol.
A] DETERMINATION OF ALCOHOL SOLUBLE EXTRACTIVE:-
5 g of macerated and air-dried coarse powder of drug was mixed with 100 ml of 95% alcohol
in a closed flask and kept for 24 hours, shaking frequently during the first 6 hours and then
allowed to stand for 18 hours. Thereafter, it was filtered rapidly taking precautions against
loss of the solvent. About 25 ml of the filtrate was evaporated to dryness in a tared flat
bottomed shallow dish, dried at 105 deg C and weighed. The percentage of alcohol-soluble
extractive was calculated with reference to the air-dried drug.
B] DETERMINATION OF WATER SOLUBLE EXTRACTIVE:-
Proceeded as directed for the determination of alcohol soluble extractive, using chloroform
water I.P. as a solvent.
C] DETERMINATION OF CHLOROFORM SOLUBLE EXTRACTIVE:-
Proceeded as directed for the determination of alcohol soluble extractive, using chloroform
as solvent.
D] DETERMINATION OF PETROLEUM ETHER SOLUBLE EXTRACTIVE:
Proceeded as directed for the determination of alcohol soluble extractive, using petroleum
ether as a solvent.
5. SWELLING FACTOR:-
Useful in the evaluation of crude drugs containing mucilage.
Useful for the detection of purity of the crude drug determination.
Procedure:-
1. Transfer 1 gm of the seeds to a 25ml of stoppered cylinder.
2. Fill up to the 20ml mark on the cylinder with water.
3. Agitate gently and occasionally during 24 hrs & allowed to stand.
4. Measure the volume occupied by the swollen seeds.
6. VISCOSITY:-
Viscosity of a liquid is constant at a given temperature and is an index of its composition. So
it can be used as a means of liquid drugs standardization.
Examples:-
Liquid paraffin – Kinematic viscosity not less 64-centistokes at 37.8 deg.
Pyroxylin – Kinematic viscosity 1100 – 2450 centistokes.
7. 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 oil, 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.
Examples:-
3. ASH VALUE:- :-
The residue remaining after incineration is called ash (Ash is a inorganic salts of carbonates,
phosphates, Silicates, of sodium, potassium, calcium and magnesium)
- Physiological ash:- The ash derived from the plant tissue itself .
- Non Physiological ash:- The residue of extraneous matter adhering to the plant
surface (sand, oil, etc).
Ash value is used to determine quality & purity of a crude drugs. The maximum temperature
used for total ash is not more than 4500c.
TYPES OF ASH VALUES:
A] TOTAL ASH VALUE:-
It is used for detecting low grade products, exhausted drugs, & excess of sandy & earthy
materials.
Procedure:-
Accurately weighed 2 gm of the powdered drug was taken in a tarred silica dish and it was
incinerated at a temperature not exceeding 450°C until free from carbon. The sample was
cooled and weighed. The percentage of ash was calculated with reference to the air dried
drug.
B] ACID INSOLUBLE ASH VALUE:-
Used for the determination of earthy matter present on roots, rhizomes, & also on the leaves.
Procedure:-
The ash obtained described as total ash was boiled for 5 min. with 25 ml of dilute
hydrochloric acid. The insoluble matter was collected on an ash-less filter paper and washed
with hot water and ignited to constant weight. The percentage of acid insoluble ash was
calculated with reference to the air dried drug.
The majority of crude drugs contain calcium oxalate whose quantity varies frequently.
Therefore Total ash of a crude drugs vary within wide limits for specimen of genuine drug.
E.g. for Rhubarb, Total ash ranges from 8-40% and in these case determination of acid
insoluble content is more preferable.
C] WATER SOLUBLE ASH VALUE:-
Used to detect either material exhausted by water or not.
E.g. Tea leaves, Ginger rhizomes etc.
Procedure:-
To the ash obtained as total ash 25 ml water was added and boiled for 5 minutes. The
insoluble matter was collected on an ash less filter paper, washed with hot water and ignited
in a crucible for 15 minutes at a temperature not exceeding 450оC. The weight of this
residue was subtracted from the weight of total ash. The content of water-soluble ash with
reference to dried drug was calculated.
D] SULPHATED ASH:-
Used for the detection of low grade products. This ash is produced after treating the drug
with sulphuric acid to get sulphate salts. Temp- more than 6000c.
4. Extractive values:-
It gives an idea about the nature of the chemical constituents present in a crude drug.
Useful for estimation of constituents extracted with the solvent used for extraction.
Employed for material for which as yet no suitable chemical or biological assay exists.
It can be done by following methods: Cold maceration, hot extraction and ethanol.
A] DETERMINATION OF ALCOHOL SOLUBLE EXTRACTIVE:-
5 g of macerated and air-dried coarse powder of drug was mixed with 100 ml of 95% alcohol
in a closed flask and kept for 24 hours, shaking frequently during the first 6 hours and then
allowed to stand for 18 hours. Thereafter, it was filtered rapidly taking precautions against
loss of the solvent. About 25 ml of the filtrate was evaporated to dryness in a tared flat
bottomed shallow dish, dried at 105 deg C and weighed. The percentage of alcohol-soluble
extractive was calculated with reference to the air-dried drug.
B] DETERMINATION OF WATER SOLUBLE EXTRACTIVE:-
Proceeded as directed for the determination of alcohol soluble extractive, using chloroform
water I.P. as a solvent.
C] DETERMINATION OF CHLOROFORM SOLUBLE EXTRACTIVE:-
Proceeded as directed for the determination of alcohol soluble extractive, using chloroform
as solvent.
D] DETERMINATION OF PETROLEUM ETHER SOLUBLE EXTRACTIVE:
Proceeded as directed for the determination of alcohol soluble extractive, using petroleum
ether as a solvent.
5. SWELLING FACTOR:-
Useful in the evaluation of crude drugs containing mucilage.
Useful for the detection of purity of the crude drug determination.
Procedure:-
1. Transfer 1 gm of the seeds to a 25ml of stoppered cylinder.
2. Fill up to the 20ml mark on the cylinder with water.
3. Agitate gently and occasionally during 24 hrs & allowed to stand.
4. Measure the volume occupied by the swollen seeds.
6. VISCOSITY:-
Viscosity of a liquid is constant at a given temperature and is an index of its composition. So
it can be used as a means of liquid drugs standardization.
Examples:-
Liquid paraffin – Kinematic viscosity not less 64-centistokes at 37.8 deg.
Pyroxylin – Kinematic viscosity 1100 – 2450 centistokes.
7. 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 oil, 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.
Examples:-
|
DRUGS
|
MELTING POINT (Deg CENT)
|
|
Wool fat
|
34 – 44
|
|
Bees wax
|
62 – 65
|
|
Colophony
|
75 - 85
|
8. SOLUBILITY:-
The presence of
adulterant in a drug could be indicated by solubility studies identify by
various solvents
1. Alcohol:-
5 gm of powdered material along with 100 ml of alcohol are shaken well occasionally for the
first 6 hours and kept undisturbed for 18 hours. The liquefied extract thus obtained was
concentrated in an vacuum oven and the percentage was calculated with the weight of
The drug powder taken.
2. Water :-
The procedure adopted for solubility percentage of alcohol is used with chloroform water
instead of alcohol to get the water solubility.
Examples:- Pure Asafoetida is soluble in carbon disulphide.
9. OPTICAL ROTATION:-
Many volatile oil and other natural products have the ability to rotate the plane of polarized
light to right or left side, like wise they are called as dextro or levorotatory. This detection of
optical rotation & its magnitude is an important criterion for the evaluation of certain drugs.
It is studied by using polarimeter at 20 deg.
10. REFRACTIVE INDEX:-
When a ray passes from a one medium to another of different density, it is bent from
original path. Thus, the ratio of velocity of light in vacuum to its velocity in a substance is
termed as refractive index of the second medium. Depending upon purity, it’s constant
for a liquid and can be consider as one of its standardization. Refractive index of a
compound varies with the wave length of the incident light, temperature and pressure.
Examples:- Ricinus communis(Castor) - 1.475-1.527 (RI).
Syzygium aromaticum (Clove) - 1.527-1.535 (RI)
11. VOLATILE OIL CONTENT:-
Pharmaceutical significance of aromatic drugs is due to their odorous principal that is
volatile oils such crude drugs are standardized on the basis of their volatile contain.
It is determined by steam distillation method by using Clevenger apparatus.
Examples:- Citrus × limon (lemon peel) - 2.5
Syzygium aromaticum (Clove) - 15
Foeniculum vulgare (fennel) - 1.4
various solvents
1. Alcohol:-
5 gm of powdered material along with 100 ml of alcohol are shaken well occasionally for the
first 6 hours and kept undisturbed for 18 hours. The liquefied extract thus obtained was
concentrated in an vacuum oven and the percentage was calculated with the weight of
The drug powder taken.
2. Water :-
The procedure adopted for solubility percentage of alcohol is used with chloroform water
instead of alcohol to get the water solubility.
Examples:- Pure Asafoetida is soluble in carbon disulphide.
9. OPTICAL ROTATION:-
Many volatile oil and other natural products have the ability to rotate the plane of polarized
light to right or left side, like wise they are called as dextro or levorotatory. This detection of
optical rotation & its magnitude is an important criterion for the evaluation of certain drugs.
It is studied by using polarimeter at 20 deg.
10. REFRACTIVE INDEX:-
When a ray passes from a one medium to another of different density, it is bent from
original path. Thus, the ratio of velocity of light in vacuum to its velocity in a substance is
termed as refractive index of the second medium. Depending upon purity, it’s constant
for a liquid and can be consider as one of its standardization. Refractive index of a
compound varies with the wave length of the incident light, temperature and pressure.
Examples:- Ricinus communis(Castor) - 1.475-1.527 (RI).
Syzygium aromaticum (Clove) - 1.527-1.535 (RI)
11. VOLATILE OIL CONTENT:-
Pharmaceutical significance of aromatic drugs is due to their odorous principal that is
volatile oils such crude drugs are standardized on the basis of their volatile contain.
It is determined by steam distillation method by using Clevenger apparatus.
Examples:- Citrus × limon (lemon peel) - 2.5
Syzygium aromaticum (Clove) - 15
Foeniculum vulgare (fennel) - 1.4
 FOR ASSESSMENT OF HERBAL DRUGS (PART - 3) T.Y B.PHARM | SEM VI | HERBAL DRUG TECHNOLOGY | PCI SYLLABUS | UNIT IV.){kind=link}
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