2. Introduction
A natural product is a chemical compound or substance
produced by a living organism.
They may be extracted from tissues of terrestrial
plants, marine organism or microorganism (fermentation)
3. Definition
Extraction involves the separation of
medicinally active portions of animal or plant
tissues from the inactive components through
the use of selective solvents.
4. Extraction is a technique used in chemical or
biochemical processes to separate two or more
different compounds (solid or liquid) based on
their relative solubilities in two different immiscible
liquid slovents (this usually applies for liquid-liquid
extraction).
Principle
5. Extraction is the treatment of the plant or animal
tissues with solvent, whereby the medicinally active
constituents are dissolved, and most of the inert matter
remains undissolved.
The solvent used for extraction is known as
Menstruum and the inert insoluble material that
remains after extraction is called Marc.
7. Maceration
In this process, the whole or coarsely powdered
crude drug is placed in a stoppered container with the
solvent and allowed to stand at room temperature for
a period of at least 3 days with frequent agitation until
the soluble matter has dissolved.
The mixture then is strained, the marc (the damp
solid material) is pressed, and the combined liquids
are clarified by filtration or decantation after standing.
9. Infusion
o Fresh infusions are prepared by macerating the crude
drug for a short period of time with cold or boiling
water.
o These are dilute solutions of the readily soluble
constituents of crude drugs.
10. Digestion
This is a form of maceration in which gentle heat is used
during the process of extraction.
It is used when moderately elevated temperature is not
objectionable.
The solvent efficiency of the menstruum is thereby increased.
11. Decoction
In this process, the crude drug is boiled in a specified volume
of water for a defined time; it is then cooled and strained or
filtered.
This procedure is suitable for extracting water-soluble, heat
stable constituents.
The starting ratio of crude drug to water is fixed, e.g. 1:4 or
1:16; the volume is then brought down to one-fourth its original
volume by boiling during the extraction procedure.
Then, the concentrated extract is filtered and used as such or
processed further.
13. Percolation
Organized vegetable drug is taken in a suitably powdered form.
Uniform moistening of the powdered vegetable drugs with
menstruum for a period of 4 hours in a separable vessel
(Imbibition).
Packed evenly into the percolator.
A piece of filter paper is placed on surface followed by a layer
of clean sand so that top layers of drugs are not disturbed.
Sufficient menstruum is poured over the drug slowly and
evenly to saturate it, keeping the tap at bottom open for passing
of occluded gas to pass out.
14. Sufficient menstruum is also added to maintain a small layer
above the drug and allowed to stand for 24 hours.
After maceration, the outlet is opened and solvent is percolated
at a control rate with continuous addition of fresh volume.
75% of the volume of the finished product is collected.
Marc is pressed and expressed liquid is added to the percolate
giving 80% to 90% of the final volume.
Volume is adjusted with calculated quantities of fresh
menstruum
Evaporation and concentration is done to get finished
products by applying suitable techniques and apparatus.
15.
16.
17. Hot Continuous Extraction (Soxhlet)
In this method, the finely ground crude drug is placed in a
porous bag or “thimble” made of strong filter paper, of the
Soxhlet apparatus.
The extracting solvent in flask is heated, and its vapors
condense in condenser .
The condensed extractant drips into the thimble containing
the crude drug and extracts it by contact.
18. When the level of liquid in chamber rises to the top of
siphon tube, the liquid contents of chamber falls from siphon
into flask.
This process is continuous and is carried out until a drop of
solvent from the siphon tube does not leave residue when evap
orated.
The advantage of this method, compared to previously
described methods, is that large amounts of drug can be
extracted with a much smaller quantity of solvent.
20. Aqueous Alcoholic Extraction by Fermentation
It involves soaking the crude drug in the form of either a powder
or a decoction for a specified period of time during which it under
goes fermentation and generates alcohol in situ.
This facilitates the extraction of the active constituents contained
in the plant material.
The alcohol thus generated also serves as a preservative.
Some examples of such preparations are Karpurasava,
Kanakasava, Dasmularista
21.
22. COUNTER-CURRENT EXTRACTION
In counter-current extraction (CCE), wet raw material is
pulverized to produce a fine slurry.
Here the material to be extracted is moved in one direction
within a cylindrical extractor where it comes in contact with
extraction solvent.
The further the starting material moves, the more concentrated
the extract becomes.
23. Complete extraction is thus possible when the quantities of
solvent, material and their flow rates are optimized.
Finally, sufficiently concentrated extract comes out at one
end of the extractor while the marc falls out from the other
end.
24.
25. Advantages
o Smaller volume of solvent as compared to other methods like
maceration, decoction, percolation.
o It is commonly done at room temperature, which spares
the thermolabile constituents from exposure to heat which is
employed in most other techniques.
o As the pulverization of the drug is done under wet conditions,
the heat generated during combination is neutralized by water.
oThe extraction procedure has been rated to be more efficient
and effective than continuous hot extraction.
26. Ultrasound Extraction (Sonication)
The procedure involves the use of ultrasound with
frequencies ranging from 20 kHz to 2000 kHz. This increases
the permeability of cell walls and produces cavitation.
The process is useful in some cases, like extraction of
Rauwolfia root, its large-scale application is limited due to the
higher costs.
27.
28. Disadvantage
The deleterious effect of ultrasound energy
(more than 20 kHz) on the active constituents of
medicinal plants through formation of free radicals is
seen and consequently undesirable changes in the
drug molecules are observed.
29. Supercritical Fluid Extraction
The critical point represents the highest temperature and
pressure at which the substance can exist as a vapour and
liquid in equilibrium.
A super-critical fluid is a substance, mixture or element,
which under certain operative conditions of pressure and
temperature and mechanical operations, is above its critical
point but below the pressure needed to condense it into a
solid.
30. Extraction via super-critical fluids is better for the
environment than conventional methods of extraction, because it
uses gases such as CO2 at high pressure, in a liquid or super-
critical state, instead of chlorinated solvents which produce
toxic waste.
Carbon dioxide is the preferred fluid for SFE.
They are powerful solvents and have a great capacity of
penetration in solids, which allows a rapid and almost complete
exhaustion of extractable solids.
31. They can easily be completely separated from extracts,
simply by modifying pressure or temperature, up to the point.
32.
33. Advantages
i) The extraction of constituents at low temperature, which
strictly avoids damage from heat and some organic solvents.
ii) No solvent residues.
iii) Environmentally friendly extraction procedure.
34. Drawback
The main drawback is the time of extraction, which is
usually long.
In fact, in some cases, it can take as much as 24 hours.
With normal fluids, extraction can be speeded up by
mechanical shaking but this presents problems when using
super-critical fluids, which limits industrial use.
