Extraction Technologies For Medicinal And Aromatic Plants - Unido

EXTRACTION TECHNOLOGIES FOR MEDICINAL AND AROMATIC PLANTS
3.3 Factors Affecting the Choice of Extraction
Process
The choice of the process to be used for the extraction of a
drug depends on a number of factors.
3.3.1 Nature of the Crude Drug
The choice to use maceration or percolation primarily depends
upon the nature and characteristics of the crude drugs to be extracted.
Therefore, knowledge of the type of organs and tissues of the plant matter
is essential for achieving the best result.
3.3.2 Stability of the Crude Drug
Continuous hot extraction procedures should be avoided when
constituents of the drug are thermolabile.
3.3.3 Cost of the Crude Drug
When the crude drug is expensive (e.g. ginger), it is desirable
to obtain complete extraction. Therefore, from the economic point of view,
percolation should be used. For inexpensive drugs, maceration, despite its
lower effi ciency, is acceptable in view of its lower cost.
3.3.4 Solvent
Selection of the solvent depends on the solubility of the desired
components of the material. If the constituents demand a solvent
other than a pure boiling solvent or an azeotrope, continuous extraction
should be used.
3.3.5 Concentration of the Product
Dilute products such as tinctures can be made by maceration
or percolation. For semi-concentrated preparations, the more effi cient percolation
process is used. Concentrated preparations, such as liquid or dry
extracts, are made by percolation.
3.3.6 Recovery of Solvent
Solvent is preferably recovered under reduced pressure to save
thermolabile constituents.
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