Evaluation /Quality Control / assessment of crude drug

 according to WHO guidelines 

(Part-III)

(Physical evaluation)

(S.Y. B. Pharm Unit -IV ) Unit -I


(T.Y. B. Pharm Sem -VI ) -Unit - IV


(Final Yr. B. Pharm) Section -II

As per PCI Syllabus 

METHODS OF DRUG EVALUATION
The evaluation of a drug is done by following methods.


1. Organoleptic evaluation

2. Morphological evaluation

3. Microscopic evaluation

4. Physical evaluation

5. Chemical evaluation
6. Analytical evaluation
7. Biological evaluation

PHYSICAL EVALUATION
q Foreign organic matter
qMoisture Content
qViscosity
qMelting point
qSolubility
qOptical Rotation
qRefractive Index
qAsh values
qExtractive values
qVolatile oil Content
qswelling factor 

Foreign matter:


Other part of the plant or other organic matter present in the drug, which is not complying, with authentic drug may be considered as foreign matter.

Other plant parts may be present due to improper harvesting and garbling. During storage insects, moulds, animal’s excreta will add to the crude drug. Medicinal plant material should be entirely free from them,  which is difficult so pharmacopoeias provide the limit for the presence of other parts of the plants.

Moisture Content

Presence of moisture in a crude drug can lead to its deterioration due to either activation of certain enzymes or growth of microbes.
Some important physical and chemical methods used to determine the moisture content in drugs are

q Loss on drying
q Karl Fischer method (chemical method)
q Azeotropic distillation method
q Spectroscopic method

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 materials Contribute to the weight loss. LOD is determining by subjecting the crude material at 105 0C to constant weight and calculate the loss of weight. 

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, lpecacauhna. The powdered material is exhausted of water with anhydrous solvents like Dioxan and aliquot is taken for titration The Karl Fischer reagent contains solution of lodine, SO2 and Pyridine in dry methanol. Iodine  is reduced by SO2 in the presence  of water causing loss dark Brown color of the reagent.


Azeotropic 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. 

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 this method ideal for the substances ‘ that contains very less quantity of water.

ll. Viscosity (Viscometer)

Viscosity of a liquid is constant at a given temperature and is an index of its composition. Hence, it is used as a means of standardizing liquid drugs.
Liquid paraffin-kinematic viscosity not less than 64-centistokes at 37.8°.
Pyroxylin-kinematic viscosity, 1100-2450 centistokes.



III. 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 oils, 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

0ptical rotation:

Many volatile oil & other natural products have the ability to rotate the plane of the 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 0C.
Along with these above physical constants other physical parameters like Melting point, Boiling point, and Freezing point etc are applied for the constituents, which are separated. Any variation in these values or active constituents shows the presence of adulterants.

Refractive index:


 It is an important parameter in the evaluation of the volatile oil & fixed oils.

RI of a substance is the ratio between the velocity of light in the air to the velocity of light in oil or substance under test.

It is given by the sine of angle of incidence to the sine of angle of refraction. RI changes  if an oil contain some adulterants.

It is generally studied at 20 0C using Abbe’s refractometer.



VII. Ash Values

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 a criterion to judge the identity OR  purity of the Crude drug.  
Muffle furnace


Types of ash values

i.Total ash value: Useful for detecting low grade products, exhausted products, excess of sandy & earthy matter with drug. 
ii.Acid insoluble ash value: Used for the determination of earthy matter present
on roots, rhizomes, and also on the leaves, Crude drugs contain calcium oxalate
crystals the amount may vary depending on the environmental conditions.

iii.Water soluble ash value: Water soluble ash value Used to detect either
material exhausted by water or not (Tea leaves, Ginger rhizomes).

iv. Sulphated ash value: Used for the detection of low grade products.

Extractive values

Crude drugs their biological activity due to the presence of active constituents, which are soluble in polar semi polar and no polar solvents. Total soluble constituent of drug in particular solvent may be called as extractive values. 

These values give idea about the extent of polar semi polar and no polar compounds present in medicinal plant materials.

Extractive values are studied by wet weight or dry weight basis by using maceration, percolation or continuous extraction using soxhlet apparatus.

Eg Water-soluble extractive values for Gentiana liquorice, etc.
Alcohol soluble extractive values for ginger, valeriana Petroleum ether, & ether soluble extractive are determined.

Volatile Oil determination:

Many Pharmacopoeias recommends minimum standards for the % of volatile oil present in number of drugs. It is determined by steam distillation method by using clavinger apparatus.

Accurately weighed amount of drug is placed in the distillation flask with water or mixture of water & glycerin,volatile oil. content present in drug  get separated at the boiling temp. of water & gets collected as a layer On the top of water which is then  measured in the graduated receiver. 



XI. Swelling Factor

Significance
•Useful in the evaluation of crude drugs containing mucilage
•Useful for the detection of purity of the crude drug  Determination. 
•Transfer 1 gm of the seeds to a 25ml stoppered cylinder.
•Fill up to the 20ml mark on the cylinder with water.
•Agitate gently and occasionally during 24 hours and allowed to stand.
•Measure the volume occupied by the swollen seeds.