2. Definition
2
Extraction is the method of removing active constituents from
a solid or liquid by means of liquid solvent.
The separation of medicinally active portions of plant or animal
tissues from the inactive or inert components by using selective
solvents.
4. In this extraction the components of the liquid mixture are
separated by contacting them with a suitable insoluble solvent
which preferentially dissolves one or more components.
Separation of the components from liquid mixture depends upon
the unequal distribution of the components between two
immiscible liquids.
In this extraction the feed solution is phase 1 and the solvent used
for extraction is phase 2.
Both the feed and solvent forms a homogenous mixture which is
separated by contacting them with one another to separate out
one of the two liquids preferentially.
This type of extraction is most widely used to separate actives and
aromatic compounds from plants.
4
Liquid-Liquid Extraction (Solvent extraction)
6. Solid phase extraction is used for isolation, enrichment and purification of
components from aqueous solutions depending upon their physical and
chemical properties.
It involves contacting of aqueous samples with a solid phase or sorbent,
where the component under consideration is adsorbed on the surface of the
solid phase prior to elution.
The extract amount is negligible compared to quantity of analyte in the
sample.
This type of extraction is widely used in analytical laboratories.
Solid Phase Extraction
6
8. Solid-liquid extraction means the removal of constituents from a
mixture of solids by bringing the solid material into contact with a
liquid solvent that dissolves these particular constituents.
Leaching may either be used for production of concentrated
solution of an active principle, or in order to free an insoluble
constituents from a soluble material with which it is contaminated.
Solid-liquid extraction
8
11. Maceration is a process that involves soaking of plant materials, usually
in powder or coarse form, in a stoppered container with a defined solvent.
The setup is left to stand at room temperature (+25 “C) for a minimum of
72 hours with shaking.
The process is conditioned to soften and breakup the plant’s cell wall in
order to liberate the soluble bioactive metabolites.
After 3 days, the whole mixture is pressed and sieved by filtration using
Whatman no. 1 filter paper.
In this method, heat is transferred by convection and conduction and the
choice of the solvent is crucial to determine the type of phytochemical
extracted from the samples.
Maceration
11
13. This is the most frequently used method to extract phytochemicals for the preparation of
tinctures and fluid extracts.
A percolator made of a narrow cone-shaped vessel open at both ends is generally used.
The solid ingredients are moistened with a specified amount of the defined menstruum and
allowed to stand for approximately 4 hours in a closed container.
The wet mass is then packed and the top of the percolator is closed and some extra
menstruum is added to form a shallow layer above the mass.
The mixture is allowed to macerate in the closed percolator for 24 hours
The outlet of the percolator is then opened and the liquid contained therein is allowed to drip
out slowly.
The percolate is mixed until it measures about three-quarters of the required volume.
The macerated product is then pressed and the expressed liquid is added to the percolate.
Properly prepared menstruum is added to produce the required volume, and any excess liquid
is eliminated by filtration or by standing followed by decanting.
Percolation
13
15. Decoction
15
• In decoction, the harvest crude product is boiled in a specified volume of
water for a defined period, cooled and then strained or filtered.
• This procedure is applicable for the extraction of water-soluble, heat stable
metabolites.
• The starting ratio of crude product to water is fixed, such as 1:4 or 1:16.
• The extract is then concentrated to one-fourth of its original volume by
boiling.
• The concentrated extract is filtered and processed further Decoction is
generally suitable for extracting heat-stable compounds in hard plant parts
such as the roots and barks.
• Decoction gives more oil-soluble phytochemicals compared to maceration
and infusion.
17. Digestion
17
Digestion is a maceration method that includes application of gentle heat
during extraction.
It is used when a moderately raised temperature is needed to increase the
efficiency of the menstruum
In this process drug is extracted by heating at a particular pressure to increase
the penetration power of the menstruum, so that there is complete extraction
of the drug.
The apparatus used is known as ‘Digestor’ which is a vessel made up of metal.
The whole of the drug is placed in the covered digestor it and bolted with the
help of nuts.
The drug is treated with menstruum for a definite period under specified
condition of temperature and pressure.
19. Infusion
19
Fresh infusions are prepared by macerating the crude drug for a short period
with cold or boiling water.
These are dilute solutions of the readily soluble constituents of crude drugs.
Infusion uses the same principle as maceration; crude drug is soaked in cold
or boiled water for shorter duration.
20. Soxhlet Extraction (Hot Continuous Extraction)
20
In this method, finely ground crude drug sample is placed in a porous bag or
thimble made from a strong filter paper or cellulose, which is placed in
thimble chamber of the Soxhlet apparatus.
Extraction solvent is heated in the round bottom flask, vaporizes into the
sample thimble, and condenses in the condenser and drip back.
When the liquid content reaches siphon arm, it is emptied into the bottom
flask again and the process is continued.
22. Microwave Assisted Extraction (MAE)
22
MAE utilizes microwave energy to facilitate partition of analytes from the sample
matrix into the solvent.
Microwave radiation interacts with dipoles of polar and polarizable materials
(solvent and sample) that causes heating near the surface of the materials and heat
is transferred by conduction.
Dipole rotation of the molecules induced by microwave electromagnetic disrupts
hydrogen bonding; enhancing the migration of dissolved ions and promotes solvent
penetration into the matrix.
In non-polar solvents, poor heating occurs as the energy is transferred by dielectric
absorption only.
MAE can be considered as selective methods that favour polar molecules and
solvents with high dielectric constant.
23. Sonication Extraction:
23
This method involves the use of ultrasound waves ranging from 20 kHz to
2000 kHz.
The mechanic effect of acoustic cavitation from the ultrasound waves
increases the surface contact between solvents and samples and permeability
of cell walls.
Physical and chemical properties of the materials subjected to ultrasound are
altered and disrupt the plant cell wall; facilitating release of compounds and
enhancing mass transport of the solvents into the plant cells.
The procedure is simple and relatively cheap that can be used in both small
and larger scale of phytochemical extraction.
24. Accelerated Solvent Extraction (ASE)
24
ASE is an efficient form of liquid solvent extraction due its minimal solvent
requirement.
Sample is packed with inert material such as sand in the stainless steel
extraction cell to prevent sample from aggregating and block the system
tubing.
Packed ASE cell includes layers of sand-sample mixture in between cellulose
filter paper and sand layers.
ASE is an automated extraction technology capable of controlling
temperature and pressure for each individual samples and completes in less
than an hour.
25. Supercritical Fluid Extraction (SFE)
25
Supercritical fluid (SCF; dense-gas) is a substance that shares the physical
properties of both gas and liquid at its critical point.
SCF behaves more like a gas but have the solvating characteristic of a liquid.
A major drawback of this method is the initial cost of the equipment which is
very high.
26. Applications of Extraction
26
It is used in the separation of antibiotics and protein recovery.
It used to recover high-boiling components such as phosphoric acid, boric
acid, and sodium hydroxide from aqueous solutions.
It is used to obtain therapeutically active constituents from plant parts and to
eliminate the inert material
It is used to isolate enzymes (renin) and hormones (insulin) from animal
sources.
Gelatin is produced by conversion of skin and bone collagen by treatment
with lime or diluted acid and is further extracted with warm water.
It is used in extraction of fixed oils from seeds.
