Evaluation methods of adulteration

Evaluation of drug adulteration means the determination of quality, purity, and identification of any drug. Many methods are available to determine the adulteration in an original crude drug. 

Evaluation Depends on-

1. Identity means to determine the exact biological source of drugs and to determine whether the drugs are from the same biological source or from different sources.


2. Purity means checking the presence of foreign material either organic or inorganic present in the drug.


3. Quality means to determine the concentration of therapeutic or pharmacological active constituent present in a drug in comparison with the standard values to show the desired therapeutic effect by the drug.

Methods of Evaluation

There are different methods present for the detection of adulteration in crude drug as follows-

1. Morphological /Organoleptic Evaluation
2. Microscopic Evaluations
3. Physical Evaluations
4. Chemical Evaluations
5. Biological Evaluations
6. Chromatography and Spectrophotometer

So let see them in detail with examples,

• MORPHOLOGICAL /ORGANOLEPTIC EVALUATION

  
  
               This evaluation is done with the help of sense organs. It includes characters like colour order shape taste special features like Touch, texture, etc. It is the easiest method for the evaluation of adulteration in the crude drug.
  
  
  Example:
  
  
  • Wavy shape - rauwolfia, disc shape- nux-vomica, conical shape- aconite, quills of cinnamon.
  • Strength of odour - musty, moldy, rancid, fruity.
  • Bitter taste gentine.
  • Pungent taste – capsicum ginger.
  • Fractured surface – cinchona cascara bark etc.



• MICROSCOPIC EVALUATION

  
  
               In it, the Powder drug is examined under the microscope to study the arrangement of tissues and characteristics of drugs. Some medicinal plant dealers create great adulterations which are very difficult to trace out and hence microscopic evaluation is very important for such evaluation.
  
  
  Example:
  
  
  • Glandular trichome of mint and warty trichome of senna.
  • Powdered clove stalk contains sclereids and Calcium oxalate crystals but the clove does not contain these chemicals.
  • Sclerenchyma absent in rauwolfia Serpentine root but presents rauwolfia micratha.
  • Stone cell present in frangula Bark and absent in cascara Bark.
  • Lignified trichome and plasmodesmata in nux-vomica.

        Quantitative Microscopy

             It is a technique to analyze the powdered drug. When chemical and other methods of evaluation fails to measure the accurate quality of drug then quantitative microscopy is used, it includes-

• Lycopodium spore method

           Lycopodium spores are very characteristic in shape and appearance and uniform in size. Powdered drug is evaluated by this method. % purity of a powdered drug is calculated using the following equation;
  
  
  \[\% Purity\: of\: drug = {{\left(N \times W \times 94000 \times 100\right)} \over {\left(S \times M \times P\right)} } \]
  
  Where,
  N- No. of characteristic structure in 26 fields.
  W-weight in mg of Lycopodium taken
  S –No. Of Lycopodium spores in 25 fields
  M- Weight in mg of sample. Dried at 105° Celsius.
  P- no. of grains in powders.
  

• Stomatal number

          It is the average number of stomata per square millimeter of the epidermis of the leaf.

• Stomatal index

           It is defined as a portion of stomata against the total number of cells in the epidermis. (Epidermal cell plus the stomata) reduced to percentage.
  
  
  \[ Stomatal \: Index = {{S \times 100} \over {E + S}} \]

• Palisade Ratio

           Palisade ratio is the average number of palisade cells below each epidermal cell in leaf.

• Vein-islet number 

           The number of vein-islets per square millimeter of the leaf surface Midway between the midrib and the margin.

• Vein-islet terminations 

           The number of Vein-islet terminations per sq. mm of leaf surface mid-way between the midrib and the margin.



• CHEMICAL EVALUATION

               It is the determination of chemical constituents in crude drug; in this method, specific chemical tests are applied to check the purity and quality of drugs.
  It involves,

  • Qualitative chemical test

                 It is the identification test for various phytochemical constituents like alkaloids, tannins.

  • Quantitative chemical

                 This test includes quantities like acid value; saponification value; Easter value; acetyl value.

  • Chemical assays

                 It includes assay of alkaloids, resins, volatile oils, glycoside, vitamins, or other constituents present in the drug.

  • Chromatography and Instrumental Analysis

                 It includes the determination of phytoconstituents using chromatography and spectroscopic methods like PC TLC HPTLC HPLC GC UV-visible IR MS.

• BIOLOGICAL EVALUATION

               When physical or chemical methods are not able to produce a satisfactory result the drugs are evaluated by biological methods of evaluation. It includes evaluation methods like bioassay, biological assay in which plant or extracted product are evaluated by various biological methods, in it pharmacological activities of the drug is evaluated, for example hot plate analgesiometer. It includes evaluation by biological methods under standard conditions.

• CHROMATOGRAPHY and SPECTROPHOTOMETER

               Spectroscopic techniques for evaluation of adulteration, different types of chromatographic techniques are available for separation and analysis of components present in a drug and to check the purity and quality of the drug for example TLC, HPTLC, HPLC, GLC, UV-visible spectroscopy, NMR, IR, mass spectroscopy.

• PHYSICAL EVALUATION

               In this type of evolution physical constants of a drug are determined wherever possible.
     It Includes:
  

  • Solubility

                 The solubility of the drug in a specific solvent is taken into consideration.

  • Melting Point

                 In this method, the melting point of the drug compared with the standard melting point of the original drug. It is helpful to check the purity of solid's fixed oils and waxes pure chemical constituents gives very sharp and constant melting points.
  
  
  • Refractive Index
    
    
                 The refractive index of the drug is compared with its standard values for the determination of adulteration by physical methods. It is very useful for the determination of adulteration in volatile oils and fixed oils. It is a physical constant that depends on changes in the speed of light measured by a refractometer.
  
  
  • Swelling Index
    
    
                 It is the volume in millimeter taken-up by the swelling of 1 gram material under specific conditions (mostly plants containing mucilage). The swelling index of test material is compared with the standard values.
  
  
  • Specific Gravity
    
    
                 It is also known as relative density. It is the ratio of a solid or liquid to the mass of an equal volume of distilled water. Specific gravity is constant for the particular material.
  
  
  • Viscosities
    
    
                 These are defined as the resistance to the flow of liquid. The viscosity of a particular liquid is constant at a constant temperature.
  
  
  • Total Ash Value 
    
    
                 The amount of residue after incineration or ignition of material is known as ash value. It helps to determine the quality of the drug. The quantity of Residue after ignition simply represents the presence of adulteration like excess of sand, earthy, or inorganic materials in the crude drug.
  
  
  • Acid-Insoluble Ash
    
    
                 In this Ash is checked for the insolubility in dilute HCl lower solubility represents the presence of earthy material which is likely to occur in roots and rhizome.
  
  
  • Water-Soluble Ash 
    
    
                 It is used to detect the presence of material exhausted by water.
  
  
  • Solvent Extraction Values
    
    
                 It determines the approximate amount of chemical constituents present in medicinal plant material when extracted with a solvent.
  
  
  • Water Extractive Values 
    
    
                 The water-soluble extractive value is used for the drug-containing water-soluble active constituents such as tannins, sugar, Plant acid, mucilage, glycoside, etc.
  
  
  • Alcohol Soluble Extractive Values
    
    
                 Alcohol is an ideal solvent for the extraction of various chemicals; the solvent strength of alcohol is from 20 to 95%. Strength has to be chosen for the particular nature of the drug to be extracted.
  
  
  • Ether Soluble Extractive Values
    
    
                 Volatile Ether soluble extractive value represents the volatile Oil content of drugs.
  
  
  • Non-Volatile Ether Soluble Extractive Values 
    
    
                 It represents fixed oils, resins, coloring matter present in the drug.
  
  
  • Moisture Content
    
    
                 It determines the moisture content in a drug. Deterioration of crude drug occurs due to the presence of moisture content in it. It is determined by Karl Fischer’s method or loss on drying method.
  
  
  • Optical Rotations 
    
    
                 A certain substance has a property to rotate plane-polarized light by a particular angle known as optically active materials. The optical activity of a particular drug is constant.
  
  
  • Foreign Organic Matters
    
    
                 The presence of excess organic material to the drug is determined by microscopic methods under 6X magnification.
  
  
  • Volatile Oil Content 
    
    
                 The Clevenger apparatus is used to determine volatile Oil content in most of the drugs the volatile Oil content is constant.

These are the methods for evaluation, Hope you like this!! and if having some issues or need any help comment it below. 

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