Introduction
Evaluation of drug means confirmation of its identity and determination of its quality and purity and detection of nature of adulteration. Evaluation of herbal drugs is an important tool in the formulation of high quality herbal products.
Methods of Evaluation of Herbal Drugs
- Authentication
- Organoleptic evaluation
- Microscopic evaluation
- Chemical Evaluation
- Physical Evaluation
- Biological Evaluation
Other parameters include:
- Chemical constituents
Most of the drugs have definite specific chemical constituents to which their biological or pharmacological activity is attributed. Qualitative and quantitative characterization of the active ingredient should be assayed using biomarkers. Defining of the biomarker has to be very specific and a lot of insight has to go into it before declaring any distinct molecule. Selection of chemical markers is crucial for the quality control of herbal medicines, including authentication of genuine species, harvesting the best quality raw materials, evaluation of post-harvesting handling, assessment of intermediates and finished products, and detection of harmful or toxic ingredients.
Marker compounds are constituents that occurs naturally in the material and that is selected for special attention (for identification or standardization purposes). Markers are chemically defined constituents of a herbal drug which are of interest for quality control purposes independent of whether they have any therapeutic activity or not. Markers may serve to calculate the amount of active component of herbal drug or preparation in the finished product. Marker compounds are pure, single isolated compounds, secondary metabolites mostly with terpenes, steroid, alkaloid, flavonoid aromatic hetero aromatic frameworks and glycosides having alcoholic, carbonyl, olefinic, acid, ester and amide functionalities highly useful for single/ crude drugs: may or may not survive in multiherbal. For quantitative studies, use of specific markers that can be easily analyzed to distinguish between varieties, remains a preferred option.
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Adulteration
Adulteration or substitution is nothing but replacement of original plant with another plant material or intentionally adding any foreign substance to increase the weight or potency of the product or to decrease its cost. Therapeutic efficacy of medicinal plants depends upon the quality and quantity of chemical constituents. There are instances when herbal remedies have been adulterated with other plant material and conventional medicines. Reports of herbal products devoid of known active constituents have reinforced the need for adequate quality control of herbal remedies. In order to try to ensure the quality of licensed herbal medicines, it is essential not only to establish the botanical identity (mainly macroscopic and microscopic) of a herbal ingredient but also to ensure batch-to-batch reproducibility. Thus, in addition to macroscopic and microscopic evaluation, identity tests are necessary. Such tests include simple chemical tests, e.g. colour or precipitation and chromatographic tests. The standardization of herbal medicines also involve several other steps like source (cultivated or wild), quality of raw materials, good agricultural practices and good manufacturing practices. These practices play a pivotal role in guaranteeing the quality and stability of herbal preparations.
- Crude fibre:
This helps to determine the woody material component, and it is a criterion for judging purity. It is also used to determine the presence of excessive woody fibre.