Extraction
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The technique used for the separation of active
constituents from a solid or liquid by using a selected solvent.
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A separation technique in which a soluble
material is separated/isolated from insoluble residue with the help of
appropriate solvent.
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Extraction is carried out to separate
medicinally active chemical constituents from plant and animal tissues.
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By extraction the desired active constituents
are efficiently dissolved and separate in the prescribed solvent from the crude
drug.
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This process is controlled by mass transfer.
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Inside the plant cells the active constituents
are present, hence the solvent used for extraction purpose must be able to
penetrate inside the cell to dissolve the required constituents.
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Similarly the solution formed must have the
capability to pore out through the cell wall and mix with the surrounding
solvent.
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In this way an equilibrium is established between
the solute inside the cell and the solvent surrounding the fragmented plant
tissues.
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The selection of solvent depends upon the
properties of the secondary metabolites.
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The active constituents or the chemical entities
of interest are collected out by this procedure.
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After the extraction procedure is carried out
the unwanted material is removed.
Terminologies used in Extraction process
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Extract: Preparation of crude drugs containing all
the chemical constituents that are of primary interest and are soluble in the
solvent.
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Marc: The solid residue obtained as a result of
extraction procedure.
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Menstrum:
Selected solvent through which extraction is carried out.
Properties of Ideal Solvent
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Solvent should be highly selected for the
compounds that are to be extracted.
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Solvent must be inert so that it couldn’t react
with the active ingredients or other ingredients present in the plant tissues
or residue.
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Should be economical i.e having low price.
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Be safe to man and the environment.
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Should have completely volatile nature.
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Should have minimum viscosity.
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Should not be miscible with water.
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Have different density as that of water.
Selection of Extraction method
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Extraction method selection through whoch
extraction would be carried out depends upon the following factors.
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Size of the sample
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Quantity of the extract required
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Estimated extraction time
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Nature of the solvent
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Cost of the extraction procedure.
Drying of Crude Drug
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Unless otherwise specified for any crude drug
the crude drug would be dried below 60◦c.
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Special care is needed after collection of crude
drug till drying so that no microbial contamination occur.
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Shade drying is preferred as compare to direct
heat exposure so that no chemical alteration take place.
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In case of sunlight drying care must be taken to
use less intense light.
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Thermo labile drugs can be dried in vacuum.
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Method of drying at low pressure is also used.
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For expensive drugs Far Infra Red drying is used
but it very expensive.
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Some times oven or hot air drying is used.
Size Reduction for Extraction Purpose
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Size reduction before extraction procedure is
very important.
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With the decrease in particle size surface area
is increased which make the drug more expose to the solvent.
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Increase in mass transfer occur with size
reduction.
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Mesh size of 30-40 is optimum size for carrying
out extraction.
Presented By
Muhammad Atif
PhD Scholar Pharmaceutical Sciences
AWKUM Mardan
Manager QA Decent Pharma islamabad
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