Physical evaluation of crude drugs in pharmacognosy

1. PHYSICAL EVALUATION OF
CRUDE DRUGS

2. • MOISTURE CONTENT
• OPTICAL ROTATION
• REFRACTIVE INDEX
• MELTING POINT
• VISCOSITY
• SOLUBILITY
• ASH VALUES
• EXTRACTIVE VALUES
• VOLATILE OIL CONTENT

3. • MOISTURE CONTENT:
• The percentage of active chemical constituents in crude drugs is
mentioned on air dried basis
• Moisture content of the crude drug is minimized in order to prevent
decomposition of crude drugs due to microbial contamination
• M.C Is determined by heating a drug at 1050C in an oven to a constant
weight
• Ex:
• Starch - 15% w/w
• Digitalis - 5% w/w
• Ergot - 8% w/w

4. • VISCOSITY:
• Viscosity of a liquid is constant at a given temperature and is an index of
its composition. Hence it can be used as a means of standardising liquid
drugs
• Ex:
• Pyroxylin – 1100 – 2450 Centistokes at 370c
• Liquid Paraffin - 64 centistokes at 37.80c

5. • MELTING POINT:
• In case of pure chemicals the melting point is sharp and constant
• Since the crude drugs contain mixed chemicals they are described with
certain range of melting point
• Kokum butter - 75-850c
• Bees wax - 62- 65 0c
• Wool fat 34 - 44 0c

6. • SOLUBILITY:
• Castor oil is soluble only in 3 volumes of 90% alcohol
• Balsom of peru is soluble in chloral hydrate solution
• Colophony is soluble in light petroleum
• Asafoetida soluble in Carbon disulphide
• Alkaloidal bases are soluble in chloroform
• Alkaloidal salts are soluble in polar solvents

7. • OPTICAL ROTATION:
• Some substances have the property of rotating the plane of polarised light
in the pure state or in the solution
• They are called as optically active
• This property is called as optical rotation
• Plane of polarised light may be rotated towards right or left
• Normally it is determined at 250c using sodium lamp as the source of light
• Ex:
• Castor oil - +75 to +80
• Honey - +3 to -15
• Eucalyptus oil - 0 to +10

8. • REFRACTIVE INDEX:
• When a ray of light is passed to one medium to another medium of
different density it bent from original path
• The ratio of velocity of light in vaccume to its velocity in the substance is
termed as refractive index
• It varies with wavelength , temperature, and pressure
• Sodium light was used at 250c
• Ex:
• Arachis oil - 1.4678 to 1.470
• Castor oil - 1.4758 to 1.527
• Clove oil - 1.527 to 1.535

9. • Ash Values:
• The residue remaining after incineration is the ash value
• It consists of in organic salts, in the form of naturally occuring or adhering
to it or deliberately added to it, as a form of adulteration
• Physiological ash: it is derived from the plant tissues
• Non physiological ash: It consists of extraneous matter like sand, soil etc
• Total ash contains carbonates, oxides, phosphates, silicates and silica

10. • Ex:
DRUG TOTAL ASH (% w/w) ACID INSOLUBLE ASH(%
w/w)
Cardamom 6.0 3.5
Cannabis 15.0 5.0
Clove 7.0 0.75

11. • EXTRACTIVE VALUES:
• The extracts obtained by crude drugs are called extractive values
• Various solvents are used to determine the extractive values
• WATER SOLUBLE EXTRACTS:
• The drugs which contains water soluble active constituents of crude drugs
such as tannins, sugars, plant acids, mucilage, glycosides etc
• Ex:
• Aloe- NLT 25%
• Glycyrrhiza - NLT 20%
• Senna Leaves - NLT 30%

12. • Alcohol soluble extractives
• Alcohol is the common solvent for the extraction of various chemicals like
tannins, resins etc
• 95% ethyl alcohol is used for the alcohol-soluble extractive
• Ex:
• Aloe - NLT 10%
• Benzoin - NLT 90%
• Asafoetida - NLT 50%

13. • VOLATILE OIL CONTENT:
• Pharmaceutical significance of aromatic drugs is due to their odourous
principles .
• Such crude drugs are standardised on the basis of their volatile oil content
DRUGS VOLATILE OIL CONTENT (%W/W)
CARAWAY 2.5
CLOVE 15
CARDAMOM SEED 4