The evaluation of crude drug is essential because,
- There may be biochemical variations in the drug
- There may be detoriation due to storage
- Substitution and adulteration may be present as a result of carelessness, ignorance etc
The crude drugs can be identified on the basis of their morphological, histological, and chemical characters. The different techniques involved in standardization of crude drugs are
Morphological and organoleptic evaluation
It refers to the evaluation of drugs by color, odor, taste, size, shape and special features like texture.
This method allows more detailed examination of a drug and their identification by their known histological characters. Microscope by the virtue of its property to magnify, permits minute sections under study to enlarge so that, leaf constants, stomatal index, palisade ratio can be determined.
These are rarely constant for crude drugs, but may help in evaluation with reference to moisture content, specific gravity, density, optic rotation, refractive index, melting point, viscosity, solubility etc.
It compromises of different chemical test and assays. The isolation, purification and identification of active constituents are the methods of evaluation. Quantitative chemical test such as acid value, saponification value etc are also covered under these techniques.
When the estimation of potency of crude drug or its preparations are done by means of measuring its effect on living organisms like bacteria, fungal growth, or animal tissue, it is known as biological effect of the drug, compared to the standard drug.
By these methods a crude drug can be assessed and further clinical trial can be recommended.