PHYSICAL EVALUATION OF CRUDE DRUGS

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

• 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

• 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

• 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

• 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

• 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

• 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

• 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

• 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

• 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%

• 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%

• 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