The process of separating medicinally active constituents of plant and animal tissues with the help of selective solvents and standard procedures is termed extraction.
The extracted products of plant tissues obtained in liquid or semisolid state (after removing the solvent) or in dry powdered form are complex mixtures of metabolites.
The extracted preparations include decoctions, infusions, fluid extracts, tinctures, semisolid extracts, or powdered extracts; these preparations are named as galenicals after Galen (a Greek physician of 2nd century)
The standardised extraction procedures involve treatment with a selective solvent (menstrum) to yield the therapeutically active constituents of crude drugs, removing the inactive ones.
The undissolved residue left behind is termed marc.
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EXTRACTION METHODS.pptx
1. Prepared By
Ms. Ashvini V. Soyam
Assistant Professor
Dr. Rajendra Gode Institute of Pharmacy, Amravati
2. Phytochemistry involves the study of chemicals (mainly the
secondary metabolites) the plants produce as a measure to protect
themselves from insects, pests, pathogens, herbivores, UV
exposure, and environmental hazards.
Phytochemistry includes the structural compositions, functions,
mechanism of actions in the living systems, and the medicinal,
industrial, and commercial applications of secondary metabolites.
Phytochemicals (derived from the Greek word phyto meaning
plant) are naturally occurring and biologically active chemical
compounds present in plants.
3. The process of separating medicinally active constituents of plant and animal
tissues with the help of selective solvents and standard procedures is termed
extraction.
The extracted products of plant tissues obtained in liquid or semisolid state (after
removing the solvent) or in dry powdered form are complex mixtures of
metabolites.
The extracted preparations include decoctions, infusions, fluid extracts, tinctures,
semisolid extracts, or powdered extracts; these preparations are named as
galenicals after Galen (a Greek physician of 2nd century)
The standardised extraction procedures involve treatment with a selective solvent
(menstrum) to yield the therapeutically active constituents of crude drugs,
removing the inactive ones.
The undissolved residue left behind is termed marc.
4. The drug extraction process is divided into the following four steps:
1) The solvent penetrates the drug,
2) The drug constituents dissolve in the solvent,
3) The solution within the cells diffuses out, and
4) The dissolved portion separates from the exhausted drug.
The menstrum used for extraction should have the following properties:
1) Chemically and physically inert,
2) Non-toxic,
3) Inexpensive, and
4) Selective, i.e., it should dissolve the desired active constituents with a minimum
of the inert material.
Water, ethanol, and their mixtures are most commonly used as they fulfil the above
mentioned considerations.
5. Extraction is the process in which the separation of the soluble constituents occurs
from insoluble substance either solid or liquid by processing with a specific
solvent.
In the extraction process there is a mass transfer process in which transfer of mass
occur from soluble material like solid to a fluid.
The different factor which effect the process of mass transfer are temperature,
agitation, size reduction and others.
The extraction may be solid extraction, solid-liquid extraction or liquid-liquid
extraction.
In the solid separation of the drug the active constituents of a solid drug are
extracted from solid substances.
In the solid liquid extraction the solid drug is extracted from a liquid solvent.
In the case of liquid – liquid extraction liquid solvent is selected to extract the
active constituents present in another liquid. Both liquid are immiscible.
6. Various extraction methods employed are:
1) Maceration, 2) Digestion, 3) Percolation,
4) Continuous hot extraction (Soxhlet extraction),
5) Supercritical fluid extraction,
6) Counter current extraction,
7) Microwave assisted extraction,
8) Ultrasonic assisted extraction,
9) Infusion and decoction,
10) Pressure cooker extraction,
11) Extraction by passage through a colloid mill,
12) Use of surface active agents in drug extraction, and
13) Expression and diacolation.
7. Maceration
The word maceration denotes softening. The maceration process (or Process M) is
used for producing tinctures, extracts, and concentrated infusions.
It is the simplest method of crude drug extraction, which was official in I.P., 1966.
Classification
1) Simple Maceration: It is a method for preparing tinctures from organised drugs,
e.g., roots, stems, leaves, etc.
2) Modified Maceration: It is a method for preparing tinctures from unorganised
drugs, e.g., oleo-resins and gum resins.
3) Multiple Maceration: It is a method for preparing concentrated extracts.
This method includes:
i ) Double maceration, and
ii) Triple maceration.
8. Simple Maceration
Simple maceration involves extraction of organised drugs having specific
cell structures, e.g., roots, stems, leaves, flowers, etc.
It is a very simple method, which does not require trained operators.
Tincture of myrrh and compound tincture of benzoin are examples of
products prepared by simple maceration.
Principle
In simple maceration, solid ingredients and the solvent are taken in a
stoppered container
Left undisturbed for at least 3-7 days with frequent agitation.
The soluble matter dissolves in the solvent,
The resultant mixture is passed through sieves or nets.
The marc retained in the sieves is pressed, the liquids are combined, and
filtered or decanted after standing.
9. Modified Maceration
Modified maceration is used for extraction of drugs having no cellular or
tissue structure, i.e., unorganised drugs ( e.g., gums, resins, gum -resins, and
oleo gum - resins).
During the extraction of unorganised drugs, the marc forms a compact mass
and retains no macerate; thus pressing the marc is not required.
In modified maceration, the final product is adjusted to a definite volume for
extracting unorganised drugs, because complete extraction of constituents
occurs within a short time period.
Since the unorganised drugs lack cellular structure, the soluble components
are in direct contact with the menstruum, thus quickening the extraction
process.
10. Modified maceration occurs in the following steps:
1) The unorganised drug to be extracted is reduced to minute particles and
placed in a closed vessel with the menstruum for 2-7 days.
2) This mixture is frequently agitated.
3) After a week, the mixture is strained and the strained liquid is filtered.
4) The marc left behind is washed with fresh menstruum and the washings
obtained are passed through the strainer and filter.
5) Menstruum is passed through the filter in amount sufficient to make up the
desired volume.
6) A dry receiver or a receiver washed with the menstruum is used for
collecting the filtrate; this is because unorganised drugs contain water -
insoluble resinous matter which gets precipitated, thus affecting the clarity of
the finished product.
11. Multiple Maceration:
The maceration process is use for the concentrated preparation where the entire
menstrum is segregated into two parts (for double maceration) or in three parts (in
triple maceration).
Each menstrum are use individually for the maceration process.
In this process the drug menstrum ratio is low and extraction is performed with
less amount of menstrum.
Kinetic Maceration:
Like the simple maceration kinetic maceration is also preceded into the room
temperature but the single difference is that the material is under constant motion.
The intensity and type of movement play important role in the maceration.
Re-Maceration:
In the re-maceration process part of the solvent is added to the drug.
After filtration process the residue is treated with the remainder solvent.
12. Digestion
Digestion is a modified maceration process .
It involves extraction at such a high temperature which does not
put adverse effects on the active ingredients.
Higher temperature enhances the solvent action of menstruum
and constant mechanical agitation of the system speed up the
attainment of equilibrium.
If at the used temperature the menstruum gets volatilised easily, a
reflux condenser should be attached to the vessel; this facilitates
the condensation of menstruum, so that it can be recovered and
returned back to the container.
13. Percolation
The term percolation has been derived from the Greek word
percolare which means to pass through .
Percolation (or Process P) is also termed lixivation.
It involves extracting the constituents of granulated or powdered
drug by slowly passing down through it a suitable menstruum.
The menstruum while travelling down the drug column under the
influence of gravity, extracts the drug particles layer-wise, which
are further replaced with the layers above as it moves downwards.
Percolation method achieves complete drug extraction.
15. The various stages involved in the percolation are following:
A) Size reduction: To assure complete exhaustion of the crude drug, the drug should
be suitably size reduced.
More surface area of the crude drug will be available to react with the menstrum.
Also helpful in uniform packing of crude drug in percolator.
Reduce the moment of menstrum in the percolator.
B) Imbibition: Imbibition is a process in which the powdered drug is kept along with
menstrum for 4 hours in a well stoppered container.
During this the menstrum penetrate into cell wall.
Initial moistening of the crude drug powder.
Imbibitions replace the interstices air which can otherwise affect the flow of
menstrum.
16. C) Packing: After imbibition the lump of crude drug must be
broken.
The lower end of percolator should be plucked with cotton and
then place the drug powder layer by layer.
The packing should be perfect, neither too tight nor too loose
which may affect the flow of menstrum.
Two third of the percolator should be cover with the drug on
which place the piece of filter paper and wash sand should be
placed on the top of the filter paper.
This prevents any type of disturbance of the crude drug by flow
of menstrum.
17. D) Maceration: Sufficient amount of menstrum should be added
after packing the percolator.
During the addition of menstrum the lower tap of percolator
should be open so that air present in the percolator is displaced by
the menstrum.
When menstrum starts to come from lower tap close the tap and
allowed to stand.
The menstrum level should be above the drug bed.
18. E) Percolation: Open the lower tap after 24 hours of maceration and collect the
menstrum from lower end until the three fourth portion of the final product is
obtained.
Meanwhile sufficient menstrum added over the powdered drug so that packed
drug does not become dry.
F) Pressing the marc: In the last, the marc should be pressed and obtain liquid is
added into the collected menstrum.
More menstrum should be added to obtain the desired volume.
Allow the liquid to stand and separate the suspended particles by filtration or
decantation.
Example- Strong tincture of ginger, tincture of belladona etc.
19. Modified Percolation
The different methods of modified percolation are discussed below:
1) Intermittent Percolation: In this method, percolation is followed by
maceration so that the menstruum and the drug particles remain in contact for a
prolonged period.
This results in greater extraction using small quantity of menstruum.
2) Re-Percolation: In this method of modified percolation, the same volume of
menstruum is used in divided quantities for drug extraction.
The active constituents of drug are completely extracted with the first
portion of the menstruum.
The percolate from the first lot is used as the menstruum for the second lot,
and this continues.
The drug powder to be extracted is divided into 4 or 5 lots.
The re -percolation method aims to extract maximum constituents using
minimum quantity of menstruum.
20. 3) Hot Percolation: This method modifies the efficiency of
percolation by applying higher temperatures, which can be
tolerated by the active constituents and the menstruum, and also
the finished product remains unaffected.
Hot percolation achieves complete extraction with little volume
of the menstruum.
Only water can be used as a menstruum in this method.
Hot percolation cannot be used for drugs whose active
constituents are thermolabile, and if a volatile menstruum is used.
21. Reserved Percolation:
In this type of percolation the initial portion which have the major
quantity of active ingredient is kept separate just like the simple
percolation process and the last one fourth amount of menstrum is
collected in another vessel and concentrated it by the method of
evaporation.
This concentrated syrupy fluid should be added into the previous three
fourth portion of menstrum.
Adjust the final volume.
The last one fourth portions contain very less amount of active
ingredient so by the help of evaporation generally we concentrate the
menstrum.
Example- Liquid extract of liquorice.
22. Continuous Hot Extraction (Soxhlet Extraction)
The apparatus for continuous hot extraction consists of a flask, a Soxhlet extractor,
and a reflux condenser.
The raw material is placed in a thimble (of filter paper) inserted in the wide central
tube of the extractor.
The drug after getting moistened with the menstruum is packed into the extractor in
a way that the extract outlet present at the bottom is not blocked.
The menstruum is placed in the flask and boiled at its boiling point.
The resultant vapours rise up the larger right tube in the upper part of the drug and
then enter the condenser, where it condenses and drops back on to the drug.
During percolation, the menstruum extracts the soluble constituents of the drug.
When the extract reaches to the top level of syphon tube, the complete percolate
syphons over into the flask.
This process is continued till the drug gets completely extracted.
24. This process has the following limitations:
1) It is not suitable for drugs having thermolabile active constituents, e.g.,
enzymes, alkaloids, anthraquinone derivatives, esters, etc., because this
extraction process requires a high temperature and also the extract in the
flask is maintained in hot condition during the entire process.
2) It is suitable only for pure solvents , constant boiling mixtures (like
alcohol - water), or solvent mixture forming azeotropes.
3) If the menstruum is an ordinary binary mixture, the vapour composition
and the liquid composition will be different.
4) It is not used if the drug to be extracted is of such physical nature that it
would block the Soxhlet apparatus, e.g., opium, gum, resin, orange peel,
etc.
25. INFUSION AND DECOCTION
These methods are now rarely used.
Infusions were prepared from vegetable drugs with water-soluble and
easily extractable constituents.
Decoction process was used for extracting vegetable drugs with water
soluble and heat –soluble constituents.
In the infusion process, the drug was moistened with water, macerated
with boiling water, the liquid was strained, and desired volume was
made.
In the decoction process, the drug was boiled with water, cooled,
expressed, the liquid was strained, and desired volume was made.
26. Pressure Cooker Extraction
In this method, the drug is initially macerated with the menstruum and then is held
for 5 -15 minutes in a pressure cooker at 15lb/sq. inch pressure.
The cooker is then cooled and the extract is removed by straining and pressing the
marc.
This method achieves complete drug extraction in comparatively less time.
It cannot be used for drugs with thermolabile constituents.
Extraction by Passage through a Colloid Mill
In this method, a drug suspension is prepared in the menstruum, macerated, and
then passed through a colloid mill running at 1500rpm speed.
On passing the drug particles through the colloid mill, direct dissolution of drug
constituents is not enhanced;
however permeability of the cell walls when they are passed through narrow
clearance of a colloid mill is increased.
27. Use of Surface Active Agents in Drug Extraction
By using surface active agents (e.g., PEG 400-monooleate,
PEG 600-monolaurate,PEG 400-dilaurate, sorbitol laurate, and
polyoxyethylene sorbitol monolaurate) in small amounts, the
extraction speed of ingredients of some drugs (e.g., cinchona,
hyoscyamus, and belladonna) is increased.
In this method, the mixture of surfactant and menstruum is
added to the powdered drug.
The entire mixture is agitated in a mechanical shaker, and the
extract obtained is separated from the marc.
28. ULTRASONIC ASSISTED EXTRACTION
The frequencies above the 20,000 Hz are known as ultrasound.
Ultrasonic waves are using in ultrasonic extraction.
These waves cause cavitations effect on the dry cell and destruct the cell wall and
release the active constituents.
When ultrasonic waves are passed through the liquid media it compresses (produce
high pressure) and rarefaction (lowpressure) to the liquid media.
Due to this process small voids or vacuum bubbles are formed in the solvent.
After certain duration these bubbles are not able to absorb more energy produce by
microwave and they burst.
At the high pressure cycle they bursted which is known as cavitation.
Due to this cavitation cell wall destructed and active chemical constituent are
extracted.
29. MICROWAVE ASSISTED EXTRACTION
The electromagnetic radiation which have a frequency 0.3-300 GHz are called
microwave.
Due to their electromagnetic property microwaves contain magnetic and electric
field.
Electric field generates heat through two simultaneously method i.e. ionic
conduction and dipolar rotation.
Microwave transfer the energy to solid matrix and solvent homogenously and very
efficiently.
Substance (solid matrix and solvent) absorb the energy as per dielectric constant.
The plant material which is present in the microwave transport solvent absorbs the
heat of microwave which causes the heating of moisture present inside the drug.
Evaporation occurs due to heating of moisture and this will produce high vapour
pressure.
This high vapour pressure crack the cell wall of plant drug and release the active
constituent into the solvent.
30. STEAM DISTILLATION
It is one of the most popular methods to separate the essential oil
from the crude drugs.
A still (large stainless steel container) contain the crude drug
material.
The steam is injected through inlet valve into the plant material
which contains the essential oil.
The inlet steel evaporates the volatile molecule.
This volatile molecule collected into the condenser.
The water molecule and volatile oil molecule can be easily
separated because they are not mixable.
