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Extraction
Extraction, as the term is used pharmaceutically, involves
the separation of medicinally active portions of plant or
animal tissues from the inactive or inert components by
using selective solvents in standard extraction procedures.
Extraction may be defined as 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.
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Purpose
The purposes of standardized extraction procedures for
crude drugs are to attain the therapeutically desired portion
and to eliminate the inert material by treatment with a
selective solvent known as menstruum.
The extract thus obtained may be ready for use as a
medicinal agent in the form of tinctures and fluid extracts,
it may be further processed to be incorporated in any dosage
form such as tablets or capsules.
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It may be fractionated to isolate individual chemical entities
such as ajmalicine, hyoscine and vincristine, which are
modern drugs.
Thus, standardization of extraction procedures contributes
significantly to the final quality of the herbal drug.
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General Terms Used
Menstrum: Solvent used for extraction is known as menstrum.
Eg; Water, Alcohol, Ether.
Marc: The inert fibrous and other insoluble materials remaining
after extraction.
Extracts: Preparations of liquid (Tinctures), Semisolid (soft
extracts),or Solid (dry extract)
Expression is the physical act of applying pressure to
squeeze out oils or juices from plants. This was normally
achieved with a tincture press.
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General Method of Extraction
1. Communition (reducing substances to small size)
2. Penetration of the crude drug by menstrum
3. Dissolution of the active principles by menstrum
4. Diffusion of the dissolved active principles
5. Separation of the dissolved active principles from the marc
by filtration or expression.
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Grinding
1. Large particles take a longer time for complete extraction than
small ones and large differences in particle size thus slow down
the extraction process.
2. Several types of machines are available for grinding crude
drugs:
3. Hammer mill; a common type for grinding crude drugs.
4. Knife mill; is useful for production of low-dust powders of
leaves, barks and roots for subsequent percolation or
maceration.
5. Tooth mill; is used for production of very fine powders.
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Hammer Mill
Knife Mill
Grinding Cont…..
1. Grinding produces a certain amount of heat which must be
observed when grinding crude drugs containing heat-sensitive
compounds.
2. Mills cooled with liquid nitrogen are available for such
purposes.
3. Cold grinding is also preferable for crude drugs containing
volatile oils.
4. Following grinding, the material must be sifted to ensure the
proper particle size.
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Choice of Menstrum
Highly selective for the compound to be extracted
High capacity for extraction
Not react with the extracted compound or with other
compounds in the plant material
Have low price
Harmless to the man and to the environment
Completely volatile.
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Generally used Solvents
Water
Aliphatic alcohols with up to three Carbon atoms
Ether
Chloroform
Glycerin
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Difference Between Water and Alcohol
WATER ALCOHOL
Advantages: Advantages:
•Cheap •Selective
•Non toxic •No additional preservatives
•Non Inflammable required
•Non toxic
Disadvantages: Disadvantages:
•Non-Selective •Costly
•Promote Hydrolysis
•Promote enzymatic
degradation
•Good media for microbial
growth
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Solvents for Extraction
Aliphatic alcohols with up to three carbon atoms, or
mixtures of the alcohols with water, are the solvents with
the greatest extractive power for almost all natural
substances of low molecular weight like alkaloids,.
According to the pharmacopoeias, ethyl alcohol is the
solvent of choice for obtaining classic extracts such as
tinctures and fluid, soft and dry extracts
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Solvents for Extraction
The ethanol is usually mixed with water to induce
swelling of the plant particles and to increase the
porosity of the cell walls which facilitates the diffusion of
extracted substances from inside the cells to the
surrounding solvent.
For extraction of barks, roots, woody parts and seeds the
ideal alcohol/water ratio is about 7:3 or 8:2.
For leaves or aerial green parts the ratio 1:1 is usually
preferred in order to avoid extraction of chlorophyll.
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Extraction processes
• It is a prolonged infusion in which drug is soaked in the
Maceration menstruum for 2-14 days
• Crude drug is placed in container (percolator) and menstruum
Percolation is added from top, which gets the active ingredients along with
it
• It is a form of maceration, which consists of application
Digestion of gentle heat
• It involves boiling of drug with water for a given time
Decoction period
• It involves pouring of hot water over drug, allowing it to
Infusion stand for sufficient time and temperature
Maceration
Definition of maceration
It is a process in which the properly comminuted drug is
permitted to soak in the menstruum until the cellular
structure is softened and penetrated by the menstruum and
the soluble constituents are dissolved.
The word maceration comes from a Latin word “macerare”
meaning “to soak”.
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Purpose of maceration
The main purpose of maceration is the extraction of drugs
from the plants.
With the maceration extraction method, the flowers are
soaked in a hot oil to have their cell membrane ruptured
and hot oil then absorb the essence.
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Process
In the maceration process, the drug to be extracted is
generally placed in a wide-mouth container with the
prescribed menstruum (drug solvent ratio: 1:5 or 1:10), the
vessel is stoppered tightly, and the contents are agitated
repeatedly over a period usually ranging from 2 to 14 days
(Minimum 3days).
Plant material (crushed or cut small or moderately coarse
powder) if necessary.
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The agitation permits the repeated flow
of fresh solvent over the entire surface
area of the comminuted drug.
An alternative to repeated shaking is to
place the drug in a porous cloth bag that
is tied and suspended in the upper
portion of the menstruum, much the
same as a tea bag is suspended in water
to make a cup of tea.
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As the soluble constituents dissolve in the menstruum, they
tend to settle to the bottom because of an increase in the
specific gravity of the liquid due to its added weight.
Occasional dipping of the drug bag may facilitate the speed
of the extraction.
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The extractive is separated from the marc by expressing the
bag of drug and washing it with additional fresh menstrum,
the washings being added to the extractive.
The process is repeated for once or twice with fresh solvent.
They are also known as galenic formulations, in honor to
Claudius Galen the precursor of preparing drugs from
plants.
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Application of maceration
The method is suitable for both initial and bulk extraction.
Disadvantage
The main disadvantage of maceration is that the process can
be quite time-consuming, taking from a few hours up to
several weeks.
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Crude Drug
i. Organized
Crude drugs with specific cell structures, like
roots, stems, leaves, flowers etc.
ii. Unorganized
Drugs having no cellular or tissue structure
and are obtained from plants as their
exudates like gums, mucilage, resins etc.
Simple Extraction
i. For organized drugs (Simple Maceration)
Take solid crude drug (coarse powder)
Take menstruum and add crude drug into it
Macerate for 7 days with occasional shaking
Obtain the extract, press the marc and combine the filtrate and expressed liquid
Stand the combined liquid for some time, followed by filtration or decantation
Examples:
Tincture of squill
Squill
Tincture of lemon
Tincture of orange
Tincture of gentian (root)
Gentian
ii. For unorganized drugs (Maceration With Adjustments)
Take powdered drug
Add menstruum (3/4 parts)
Macerate the drug for 2-7 days with occasional agitation
Filter the menstruum
Add remaining menstruum through filter paper (having unpressed marc)
Adjust the final volume
Examples:
Tincture of benzoin
Tincture of tolu Tolu
Tincture of myrrh
Benzoin
IMPORTANT
Marc is NOT pressed
Multiple Extraction
Multiple maceration OR Repeated maceration OR maceration process for concentrated
preparations
More effective than simple maceration ( as left amount of drug in marc during 1st cycle
of maceration can be extracted out during the next maceration)
Solvent Alcohol
Repeated maceration is done by:
a. Double Maceration (E.g. Conc. Infusion of Gentian)
b. Triple Maceration (E.g. Liq. Extract of Senna)
Double Maceration
The maceration of drug is carried out twice
The total volume of menstruum is subdivided in 2 parts in such a way that same quantity
of menstruum is used for each maceration.
The marc press and the liquid obtained after 1st and 2nd macerations are combined
together, filtered and evaporated to get the product of required concentration.
EXAMPLE:
Concentrated compound infusion of gentian
Triple Maceration
The maceration of drug is carried out thrice
The total volume of menstruum is subdivided in 3 parts in such a way that same
quantity of menstruum is used for each maceration.
IMPORTANT:
The marc is pressed after 3rd maceration
Liquid (macerate) obtained after 2nd and 3rd macerations are combined together
and evaporated before adding in the 1st macerate
EXAMPLE:
Concentrated infusion of Quassia (bark)
Liq. Extract of Senna leaves
Percolation
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Percolation
Percolation is derived from the Latin word “per” meaning
through and “colare” meaning to strain.
Percolation is a process in which comminuted drug is
extracted of its soluble constituents by the slow passage of
solvent through a column of the drug.
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Percolation Introduction
During percolation the drug is
packed in special suitable
apparatus termed as “Percolator”
The collected extractive is called
as “Percolate”
Most of the drug extractions are
performed by Percolation.
Ex. Preparation of Coffee
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Percolators
Percolators vary in their size, shape, capacities, composition
and utility.
For industrial scale (Large scale extraction) mainly stainless
steel and glass-lined metal percolators are used having
different size and operation.
Percolators used for extraction of leaves have 6-8 feet in
diameter and 12-18 feet in height.
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Percolator
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Percolators
Sometimes percolators are also equipped with pressure that
is used to force the menstruum through the drug column.
On small scale, glass percolators (capacity up-to 1,000g)
may be used
The shape of such percolators are different including;
Cylindrical (use less amount of menstruum)
Round
Conical or funnel shaped
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Percolator
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Packing
• A piece of cotton wool etc. (previously moistened with menstruum) is placed on
the false bottom of the percolator.
• A small amount (about 10%) of the moistened drug is introduced into the
percolator
• It is pressed lightly with rod or any other suitable device, to give even
compression.
• More moistened drug is introduced and pressed till whole of the drug is packed
in the percolator.
• After suitable packing of the drug into the percolator a piece of filter paper is
placed over top of it
• small quantity of washed sand is placed over filter paper to prevent disturbance
of the packed material
Maceration
After packing, sufficient menstruum is added to saturate the
material
Top of the percolator is covered with a lid.
When the liquid begins to drip from the bottom of
percolator, the tap (fitted at its bottom) is closed.
More of menstruum can be added at the top to maintain a
layer of menstruum over the drug.
The percolator is then set aside for 24 hours to macerate
the drug.
Advantages
More complete extraction of constituents
Shorter processing time
Increased flexibility in processing.
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Disadvantages
fine powders and materials such as resins and plants that
swell excessively (e.g., those containing mucilages) can clog
the percolator.
if the material is not distributed homogenously in the
container, the solvent may not reach all areas and the
extraction will be incomplete.
Incompatibility of percolation with certain herbs
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Complete Extraction Test
Tests to check complete exhaustion of the drug:
Take a few ml of the last percolate and evaporate to dryness,
if no residue remains - it shows that the drug is completely
exhausted.
Specific chemical tests may be performed on the percolate
for the drugs containing alkaloids, glycosides, tannins,
resins or bitter constituents.
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Percolations for concentrated
preparations
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Continuous Extraction
This procedure is considered as the most common method
used for the extraction of organic constituents from dried
plant tissue.
Soxhlet extraction Apparatus is commonly used for
continuous extraction.
It can be used both on laboratory and industrial scales.
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Soxhlet Apparatus
A piece of laboratory apparatus invented in 1879 by Franz
von Soxhlet.
Originally designed for the extraction of a lipid from a solid
material.
However, a Soxhlet extractor is not limited to the extraction
of lipids.
Typically, a Soxhlet extraction is only required where the
desired compound has a limited solubility in a solvent, and
the impurity is insoluble in that solvent.
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SOXHLETAPPARATUS
Advantages
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.
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References
Remington’s Pharmaceutical Sciences.
Cooper & Guns Dispensing
Cooper & Gun’sTutorial.
Bentley’s Text Book of Pharmaceutics.
http://www.fkog.uu.se/course/a/biolakt/biolakt-archive/BiolAkt%202010-
2/StudentpresentationerHT2010%20%28kopia%29/BiolAktHT2010_Extraktion
NatProd_Yassir_Suzan/Extraction%20of%20natural%20products_files/Page470.
htm
https://www.inkling.com/read/ansel-pharmaceutical-dosage-form-drug-
delivery-9th/chapter-13/extraction-methods-for.
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