Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev

3 MACERATION, PERCOLATION AND INFUSION TECHNIQUES FOR THE EXTRACTION OF MEDICINAL AND AROMATIC PLANTS
3.4 Quality Assurance: the Extraction Process
and Solvent
The type of extraction procedure also plays a decisive role in
determining the qualitative and quantitative composition of the extract. Some
important points regarding the quality of the extracts need to be considered:
i) The more exhaustive the extraction, the better is the yield of
the constituents from the herbal drugs.
ii) If maceration is facilitated by stirring and by use of comminuted
material, the additional stirring and shearing forces
may lead to better extraction.
iii) Other factors determining the quality of the extracts are extraction
time, temperature and solvent volume.
iv) Some drugs (e.g. Hypericum spp.) are extracted very slowly
so that exhaustive extraction can only be achieved by percolation
or multistage motion extraction. In many cases,
the transfer of quality-relevant constituents from the herbal
drugs to the extract (i.e. extraction rate) can be considerably
improved by raising the temperature. Hypericin, pseudohypericin
and biapigenin are extracted better at higher temperature
and with longer extraction times.
v) The quality of the extracts and the spectrum of constituents
obtained by maceration or digestion (i.e. maceration at higher
temperature) are also influenced by the ratio of herbal drug
to solvent. The quantity of extracted matter increases with
the volume of extraction solvent. For example, maceration of
Salvia officinalis flowers achieves almost exhaustive extraction
and thus the full spectrum of constituents obtained with
percolation can be achieved with a drug:solvent ratio of 1:20.
vi) The composition of an herbal extract depends on the type,
concentration and elution strength of the solvent. The spectrum
of constituents may vary considerably depending on
the hydrophilic or lipophilic nature of the solvent.
3.5 Maceration Processes (Steady-state
Extraction)
3.5.1 General Procedure
The general process of maceration on a small scale consists
of placing the suitably crushed plant material, or a moderately coarse powder
made from it, in a closed vessel and adding the selected solvent called
menstruum. The system is allowed to stand for seven days, with occasional
shaking. The liquid is then strained off and the solid residue, called marc,
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