Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev

3 MACERATION, PERCOLATION AND INFUSION TECHNIQUES FOR THE EXTRACTION OF MEDICINAL AND AROMATIC PLANTS
forms. These extracts are also used as sources of therapeutically active
chemical constituents for various dosage forms of modern medicines.
Historically, galenical preparations were much more extensively
used than they are at the present time. Nonetheless, due to resurgence in
interest of herbal drugs throughout the world, these extraction procedures
are still relevant and are mentioned in offi cial and unoffi cial monographs
about drug preparations. The preparations involving these procedures are
primarily intended for extemporaneous dispensing and must be freshly prepared,
due to the fact that they rapidly produce a deposit because of coagulation
of inert colloidal material and readily support microbial growth due to
absence of preservatives.
This article describes the principal methods of extraction by
maceration, percolation and infusion as well as the modifi cations in these
procedures for small-scale, offi cial and large-scale extraction. In addition,
the paper discusses the choice of extraction method, quality assurance, and
factors affecting the extraction procedures.
3.2 General Principles and Mechanisms Involved
in Crude Drug Extraction by Maceration,
Percolation and Infusion
The general principles and mechanisms involved in maceration,
percolation and infusion for the extraction of the crude drugs are same
as to those for the extraction of soluble constituents from solid materials
using solvent, which is generally referred to as leaching. The processes of
leaching may involve simple physical solution or dissolution. The extraction
procedures are affected by various factors, namely the rate of transport of
solvent into the mass, the rate of solubilization of the soluble constituents
by the solvent, the rate of transport of solution out of the insoluble material.
The extraction of crude drugs is mostly favored by increasing the surface
area of the material to be extracted and decreasing the radial distances
traversed between the solids (crude drug particle). Mass transfer theory
states that the maximum surface area is obtained by size reductions which
entail reduction of material into individual cells. However, this is not possible
or desirable in many cases of vegetable material. It has been demonstrated
that even 200 mesh particles contain hundred of unbroken cells with intact
cell wall. Therefore, it is pertinent to carry out extraction with unbroken cells
to obtain an extract with a high degree of purity and to allow enough time for
the diffusion of solvent through the cell wall for dissolution of the desired
solute (groups of constituents) and for diffusion of the solution (extract) to
the surface of the cell wall.
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