Extraction Technologies For Medicinal And Aromatic Plants - Unido

3 MACERATION, PERCOLATION AND INFUSION TECHNIQUES FOR THE EXTRACTION OF MEDICINAL AND AROMATIC PLANTS
During maceration of organized drugs, the marc is pressed because
a considerable proportion of liquid adheres to it and cannot otherwise
be separated. Moreover, the volume is not adjusted because a variable
amount of liquid containing soluble matter is left in the marc. If the volume
is adjusted, a weak product will result. Omitting adjustment, the volume of
liquid expressed infl uences the product yield and the percentage of soluble
matter, regardless of the effi ciency with which the marc is pressed in a hand
press, screw press or hydraulic press; the strength of the product is not
affected. Preparations made by this processes include vinegar of squill (British
Pharmaceutical Codex, BPC), oxymel of squill (BPC), tincture of orange
(Indian Pharmacopoeia, IP), tincture of capsicum (BPC), compound tincture
of gentian, tincture of lemon, and tincture of squill (BPC).
In maceration of unorganized drugs, the marc is not pressed
because the desirable material is mostly dissolved and the remaining marc
is gummy and slimy. Thus, it is neither practicable nor necessary to press
it. Moreover, the volume is adjusted because the clear upper layer is easily
separated by fi ltration from the lower layer. The solution contains practically
all the soluble matter of the drug; the small amount adherent to the gummy
matter is recovered when the marc is washed by menstruum in the fi lter.
Therefore, adjustment of volume leads to uniformity. Preparations made by
this process include compound tincture of benzoin, tincture of myrrh (BPC),
and tincture of tolu (BPC).
3.5.3 Modifi cations to the General Processes of
Maceration
Repeated maceration may be more effi cient than a single maceration
process, as described earlier, because an appreciable amount of
active principle may be left behind in the fi rst pressing of the marc. Double
maceration is used when the active constituents are particularly valuable
and also when the concentrated infusions contain volatile oil. Where the
marc cannot be pressed, a process of triple maceration is sometimes employed.
The total volume of solvent used is, however, large and the second
and third macerates are usually mixed and evaporated before being added
to the fi rst macerate.
3.5.4 Large-scale Extraction Procedures
For large-scale, industrial extraction, certain modifi cations are
warranted. When the extraction vessel contains a small amount of solvent
(500-1000 ml), occasional shaking is no problem. But, for industrial work
where a large amount of solvent and huge vessels are involved, shaking the
vessels is diffi cult. Obviously, there are alternative methods of agitation that
are just as effective and much simpler to put into practice. In addition, economics
become increasingly important and one of the most important objectives
is to improve the effi ciency of extraction so that less solvent is needed
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