Evaluation of crude drugs

Transcription

1 Evaluation of crude drugs

2 Physical evaluation Solubility Specific gravity Melting point for solid Refractive index for liquids Water content :- by drying the substance to constant weight in an oven ex:- hematotropine Hcl when heated to 1.05c for 2 hr. in an oven it must not loss more than 1.5 %of its weight

3 Chemical evaluation A number of chemical methods are used to evaluate of main constant of drugs and include :- a) Qualitative chemical tests : b) Quantitative chemical tests

4 Qualitative chemical tests : This test depend on color reaction or production certain color when treated with certain chemical reagents Ex:- Anthraquinone glycoside (found in senna, cascara, aloe, rhubarb) +KOH = red color The intensity of the red color depend on concentration of active constituent Drug containing alkaloids such as Atropa belladonna +dragendroffs reagent (orang-red color ), mayers reagent (white precipitate) Drug containing carbohydrate (CHO) +molish reagent =violate color (molish consist of α-naphthol and concentrated H 2 SO 4 Drug containing tannins (such as pomegranate ) + ferric chloride (Fecl 3 5%) =green color

5 Note :- green color depend on structure of tannins which depend on number of hydroxyl group This molecule give blue color This molecule give green color

6 Quantitative chemical tests These tests are applied on non cellular products such as (fixed oil, volatile oil, waxes, balsam ). The most important quantitative tests are :- 1- Acid value :- it s the number of mg of KOH potassium hydroxide required to neutral 1 gm of an acid and its depend on it M.WT. and number of carboxyl group in its molecule ex:-oxalic acid about 124, acetic acid 93 2-Iodine value :- its measure of unsaturated the iodine value is the number of parts of iodine absorbed by 100 parts by weight of the substance. it s useful constants for acids, fixed oil and waxes and help to indicate the composition of complex mixture as well as pure substance

7 3-Saponification value :- in the case of fats and waxes the term saponification value is used since the fatty acids from soap. In these cases the number of milligram of potassium hydroxide (KOH) used to neutralize the free acids present in the sample plus that required for hydrolysis of the esters. 4-Aster value : (which is characteristic of each ester ) it s the number of mgs of potassium hydroxide (KOH ) required to neutralize the acids resulting from the complete hydrolysis of 1 gm of the substance.

8 5-Chemical assay :- this method applied for the evaluation of crude drugs which are similar for those applied for assays of pure chemicals (gravimetric or colorimetric or titrimetric,, etc) Ex:-in assay of belladonna or opium,the total alkaloids of belladonna or opium can be determined (quantitatively )by acid base titration or back titration. in chemical assay the drug must be obtain in very pure form.

9 Spectroscopic or spectrometric analysis Many of spectroscopic method are used to evaluate of crude drugs which based on the isolation of a certain constituent in pure form In general spectroscopic evaluation of organic compounds based on the molecules of organic compound has the ability to absorb light or energy at a certain wave length. If U.V. or I.R. is passed throw a sample of organic compound some of light is passed throw the sample and some are absorbed. If we plot the absorption of light against the wave length we can get a certain spectrum depend on the type of energy either U.V. or I.R also on certain constituents.

10 Therefore the different compound give different absorption spectrum according to their chemical structure or composition such as Quercetin have λ max (maximum absorption at wave length )=255 nm were as kaenpherol have λ max = 288nm The alkaloid Strychnine have λ max=262nm Brucine have λ max=300nm Note :- only compound have double bound can be absorbed U.V light

11 So the spectroscopic is important for identification and evaluation of purity of compound constituents which should be obtained very pure state Fluorimetric and colorimetric analysis Also used in identification or analysis of organic compound Colorimetric analysis depent on measurement of color produce by certain compound Fluorimetric analysis depend on measurement of fluorescence produced by material or substance expose to U.V light The intensity of color produce by colorimetric and intensity of fluorescence produce by flourimetric is related or proportional to the concentration of substance.