Lecture ( 11 C )
Drug evaluation
Evaluation of drug means confirmation &comply of drug &determination of its quality,purity &detection of nature of adulteration.
Evaluation of crude drug is necessary because of three reasons:
1-biochemical variation in the drug.
2-deterioration due to treatment &storage
3-substitution &adulterationituent present ,as a result of carelessness, in the
Evaluation include ;method of estimating active constitutent present in the crude drug ,in addition to its morphological µscopic analysis,its possible to perform physical evaluation of crude drug ,the biological behavior of crude drug ,extracts, determine pharmacological evaluation.
The crude drugs can be identify by:
1-Morphological or organoleptic evaluation:
It refers to evaluation of drugs by colour ,odour ,taste ,size ,shape&special features like touch texture.....etc
Organoleptic evaluation means conclusion from the study of the result .
The general appearance of the lot of a crude drug indicates whether its likely to comply with standard. e.g fractured surface in cinchona &cascara are important characteristics .
Aromatic odour of fruit &sweet taste of liquorice are important in evaluation ,disc –shaped structure of nux-vomica ,conical shape of aconite are important in diagnosis .
The wave shape of rouwolfia &ginger ,brown colour of cinnamon , odour &taste of spice drug like black pepper ,nut meg ,caraway …..etc are also important diagnostic organoleptic charactorstics.
2-Microscopic evaluation (histological)
It can be used to identify the organized drug in powdered form by their histological characters,various reagents &stains can be used to distinguish cellular structure ,this evaluation also covers study of the constituents by application of chemical method to small quantities of powdered drug (called chemo microscopy).
3-chemical evaluation
It consist of different chemical tests& chemical assay .The isolation, purification & identification of active constituents are chemical methods of evaluation.
Quantitative chemical test like acid value, saponification value , sulphated ash ,ester value ,acetyl value are useful in evaluation resins,balsams &volatile oil….etc,
Qualitative chemical tests are useful in detection of adulteration ,these specific test like balsams &waxes is detected by copper acetate murexide test for purine bases……etc,
The purity of crude drugs is detect by quantitative estimation of active constituents present in drugs for example titrimetric estimation to estimate of alkaloid in crude drugs ,ester& aldhyde content of volatile oils ….etc
The method may be useful in determining single active constituent or the group of related constituents present in the same drug.