2. INTRODUCTION
• GALENICALS PREPARATION
• Sometimes single ingredient is extracted
from the crude drugs. When all possible
ingredients present in Crude drug are
required then the extraction may be
done in the form of dry extract, viscous
soft extract, infusion, conc. Infusions or
tinctures. These crude extracts are
known as GALENICALS
3. ` General method of Preparation:
1- Comminution (reducing substances to small
size).
2- Penetration of the crude drug by the menstrum.
3- Dissolution of the active principles by the
menstrum.
4- Diffusion of the dissolved active principles
through the cell wall to the surrounding
menstrum.
5- Separation of the dissolved active principles
from
the marc by straining, filtration or expression.
5. EXTRACTION
Separation of soluble active principles from the crude
drugs, plants or animal origin, using appropriate
solvents.
Types of Extraction
I- Solid-Liquid Extraction
a) Leaching Process
Maceration
Percolation
b) Digestion
c) Decoction
d) Infusion
II- Liquid-Liquid Extraction
a) Counter-current Extraction
6. Mostly synthetic drugs have replaced natural drugs. Some drugs
belonging to Alkaloids, glycosides, Fixed Oils, Volatile Oils, proteins
and polypeptides are still used and obtained by extraction.
Need for the separation of active principles:
Potency of the drug may be known and is more
rapidly controlled.
Deterioration by enzyme is diminished.
Drug can easily be formulated into required dosage
form
Dosage form is more stable, elegant and palatable.
Tablets cannot be manufactured from crude drugs.
Injectable from crude drugs are undesirable rather
very dangerous.
Bulk (volume/amount) smaller bulk can easily be
controlled/shipped and so reduces the cost of the drug.
7. Some important points:
Hot solvent is used both in maceration and percolation.
Selection of solvent should be done carefully to have
maximum extraction avoid undue destruction of active
principles,
Use of hot solvent for longer period of time because
extraction of certain drugs like fixed oils and alkaloids
etc. requires this treatment due to less penetration of
solvent into the cellular structure. Poor solubility of
active principles in solvents like chloroform, ethanol etc.
8.
9. PHARMACEUTICAL APPLICATION
Why is the extraction method important in
pharmacy?
Basic extraction procedures are used for
crude drugs only to obtain therapeutically
useful components and to remove inert
components by treating them with a
selective solvent known as Menstruum.
11. Infusion
Definition:
Infusions are dilute solutions containing the readily soluble constituents of
crude drugs.
Process:
It is a process of steeping or drenching a drug in water so as to extract the
active principles.
It involves pouring water over the drugs and then allowing it to keep in
contact with water for the stated period (15 min) with occasional stirring
and finally filtering off the liquid. Fresh infusion is prepared by macerating
the drug for a short period of time with cold or hot (boiling) water.
Concentrated infusions are prepared by a modified percolation or
maceration process.
Infusion pot:
It consists of covered jar (made of earthenware, stainless-steel, ceramic,
glass, porcelain) to which is fitted at certain height a perforated tray upon
which the crude drug may be allowed to rest in water being poured over it.
12. ` APPARATUS
Consist of covered jar ( made of
earthenware, stainless steel,
ceramic, glass, porcelain…) to which
is fitted at certain height a perforated
tray upon which the crude drug may
be allowed to rest in water being
poured over it.
> The plant may be enclosed loosely
in a small muslin bag and suspended
in the jar at a height where it will be
just covered by the liquid.
13. The simplest of all methods of extraction
• A definite weight of the crude drug in a certain state of
subdivision (cut small, powdered…) is prepared
• The calculated amount of hot or boiling menstrum (usually
water) is added to the crude drug
• Soak for a definite time
• During the period of infusion, the heat should be retained in
the container and the content should be stirred
• After the time of infusion, the liquid is poured off or strained
• Do not press or squeeze the marc otherwise colloidal cell
contents may be forced out giving a cloudy infusion
• Such fresh infusion should be used within 12 hours.
EXAMPLE
Preparation
1- Fresh (Dilute) Infusion
Rx.
Gentian, thinly sliced …………………….12.5gm
Dried bitter orange peel, cut small……12.5gm
14. •To avoid rapid decomposition to which the fresh (dilute)
infusions are subjected.
•These preparations are not made by the concentration of
the dilute infusion by evaporation, since thermal
treatment will result in loss of the volatile principles.
•Concentrated infusions prepared with alcoholic menstrum
or contain alcohol as a preservative.
•Concentrated infusion are not intended to be dispensed
in the concentrated state, but upon use, are diluted with
at least seven times their volume of water.
EXAMPLE:
2- Concentrated (stock) infusion
Concentrated infusion of Quassia
Rx.
Quassia, cut small………………..80 gm
Alcohol (90%)…………………….250 ml
Distilled water, cold Q.S to……...1000 m
16. PHARMACEUTICAL APPLICATION
Infusion therapy is the administration of
medication or fluids in a controlled method. It's
done most often intravenously or subcutaneously.
Since the timing can be controlled, it's used to
deliver chemotherapy drugs and other
medications that need to enter
your system slowly .
19. DECOCTION
Definition:
Solutions of the water soluble
constituents of plant drugs prepared
by boiling the drug with water.
For extraction of drugs with water
soluble and non- volatile
constituents, and drugs of hard and
woody nature.
STORAGE:
Should be freshly prepared.
20. •Process:
•In this process, the crude drug is boiled in a specified volume
of water for a defined time (10 minutes) it is then cooled and
strained or filtered.
•This procedure is suitable for extracting water-soluble, heat-
stable constituents and drugs of hard and woody nature. This
process is typically used in preparation of Ayurvedic extracts
called quath or kawath.
•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
21. Example: Cinchona bark (contains quinine)
Uses: treatment of fever, malaria and as appetite
Stimulant.
PHARMACEUTICAL APPLICATION
For internal use a decoction of the root is advised as
being the more powerful, to relieve difficulty of
breathing and soothe coughing spasms, having
'extensive use' in inflammation of the kidneys or
bladder, for the stone and gravel and where difficulty
is experienced in the passing of urine.
22. ADVANTAGES OF DECOCTION
Decoction can be used to make
tisanes
tinctures and similar solutions
DISADVANTAGES OF DECOCTION
water is not a good solvent for many of the
active components in herbs
23. 23
Comparison between infusion and decoction
Item Infusion Decoction
1- Plant Soft structure (ex. Senna
leaves)
Hard woody structure
(ex. Cinchona bark)
2- Menstrum Boiling or cold water Boiling water
3- Procedure Infusing the drug with cold
or hot water
Boiling the drug with
water
4- Time Calculated as soon as water
is added to drug
Calculated as soon as
the water begins to boil
5- Adjustment
of final volume
No adjustment Adjustment is necessary
6- Apparatus Infusion earthenware pot Any covered apparatus
7- Storage Used fresh within 12 hours Used fresh and when
stored in refrigerator
used within few days
24. Digestion
Process:
In this process the plant cells are subjected to the effect of menstruum at 40
to 60°C (higher temperature than that used for maceration and lower
temperature than that used in infusion and decoction) for longer period than
that for infusion and decoction.
Apparatus:
Thermos bottles (for maintenance of a definite temperature over the
prescribed period of time)
Advantage:
Increasing the solvent power of extraction by keeping the liquid hot
throughout the period of extraction without causing damage to the drug
constituents.
26. FLUID EXTRACTS:
Liquid extracts/ preparations of vegetable drugs containing alcohol as
solvent, preservative or having both of the qualities.
Drugs are prepared by various methods of USP.
Extracts:
Concentrated preparations of vegetable or animal origin obtained by
extraction employing suitable menstruum. And the potency of the
extract is maintained later on.
Types of extracts:
There are three major types or forms of the extracts;
1)Semisolid or semi liquid of syrup consistency
e.g. hyoscyamus extract.
2)Plastic masses known as pilular or solid extracts
e.g. glycyrrhiza extract.
3)Dry powder known as powdered extracts
e.g. belladonna extract.
27. Preparation of extracts
Extracts can be made by various methods but most of the extracts are
prepared mainly by percolation.
Percolate is concentrated by;
Evaporating whole of the drug solution in case of thermostable drug.
Under reduced pressure in case of thermolabile drugs.
Reserved percolation in case of thermolabile preparations.
Continuous extraction both hot and cold.
Extracts made by reserved percolation:
All are liquid preparations prepared by taking alcohol as menstruum.
Products are adjusted to the specified volume, while the unreserved portion
is evaporated under reduced pressure.
Example:
Liquid extract of belladonna, Liquid extract of ipecacuanha etc.
Extracts prepared other than reserved percolation:
These are of two types;
1. Unstandardized extracts
2. Standardized extracts
28. 1. Unstandardized extracts:
These are prepared by percolation to exhaustion followed by removal of
solvent to specified extent. Dry and soft extracts may also be prepared.
Evaporation is done under reduced pressure where it is necessary. Aqueous
solvent is usually used.
Example: Liquid extract of senega, Liquid extract of glycyrrhiza.
2. Standardized extract:
After the evaporation of drug by and appropriate method extracts are adjust
to a specific standard. Active principles are adjusted up to a specific
standard. Normally alcohol is used as solvent.
Example: In extract of belladonna the specified percentage of alkaloid is 1%.
Extracts prepared by maceration:
In this process whole drug is macerated in whole of the solvent.
Example: Liquid extract of senna, compound extract of colocynth.
Extracts made my digestion:
Digestion process is rarely exploited for the preparation of the extracts.
Example: Extract of malt, it helps in the digestion of fatty food due to the
presence of enzymes in it.
29. Extract of animals:
Extraction is accomplished by using appropriate process and solvent.
Example: Extract of ox bile, Extract of Liver.
Packaging and Storage of Extracts:
They must be packaged in;
Wide mouth containers or plastic tubes and closely tight to prevent loss of
moisture which would result in it’s becoming hard and unstable for use.
They must be kept at cool and dry place.
ADVANTAGES
1- Detoxifying The Metabolic Waste: Phytochemicals and antioxidants in
leaves of plants such as Kenaf (Gongura), Guava, and so on will directly
participate in biochemical reactions occurring in our bodies and assist in
excreting some metabolic waste.
2- Enhancing Immunity: It is a molecular process that produces antibodies
that combat various diseases. Drinking decoctions of different leaf types will
introduce various antigens into the bone marrow, which produces blood
cells. A wider variety of leaves is used for decoctions; thus, various antigens
are introduced, and antibodies are produced
30. DISADVANTAGES
1-The major disadvantage of infusions or decoctions
is that water is not a good solvent for many of the
active components in herbs. This problem is
compounded by the relatively short extraction time
used in their preparation (usually 5 to 10 minutes).
EXCIPIENTS
32. DEFINITION:
Tinctures are alcoholic or hydro alcoholic solutions of
vegetable materials or prepared from chemical substances
(e.g. tincture of iodine).
PROCESS:
A product is called tincture when it contains 45% v/v or more
alcohol. Tincture ipecacanha is an exemption containing
about 23% v/v of alcohol. Generally a tincture contains
alcohol ranging 20% - 90% v/v alcohol. Four parts by of
volumes product represents one part by weight of the drug.
(Strong ginger is an exception having 2 parts to 1 part of the
drug.)
INGREDIENTS:
1- BENZOIN EXTRACT
2- ETHANOL
3-ALOE EXTRACT
33. EXAMPLE:
• VANILLA TINCTURE
• BELLADONNA TINCTURE
SOLVENT:
Alcohol is used as solvent in the preparation of
tinctures because;
Many of the active principles are readily soluble in
it.
Alcohol prevents decomposition of the products
and hence the potency of the drug remains
protected.
Gums and aluminous matters are precipitated
therefore clear solutions are obtained
34. Preparation of tinctures:
They are considered stable preparations as they have sufficient
amount of alcohol to resist the microbial growth. Tinctures can be
prepared by various methods;
1. By Dilution/ Simple Solution:
Tinctures can be prepared by the dilution method from the
concentrated extracts. Solute is dissolved in the solvent with
agitation, and then filtered off.
Example:
Iodine, Thimerosal, Green soap tinctures.
2. By Maceration:
Tinctures can also be prepared by;
From the maceration of organized drugs
EXAMPLE: Tincture of Aurantii
From the maceration of unorganized drugs
EXAMPLE: Tincture of benzoin
35. 3. By percolation:
Tinctures can also be prepared by the percolation of the crude drug in
percolator.
Example:
Tincture of Belladonna, Tincture of Digitalis.
USES OF TINCTURES:
They are orally taken to relieve a wide range of
health issues or as proactive way to support specific
elements of your wellbeing.
36. ADVANTAGES OF TINCTURES:
• They are easy to store.
• They are easy to ingest.
• They are easy to dose in small quantity through dropper.
Disadvantages of tinctures:
Unpleasant tasting
Physician will prefer single drug instead of preparation from
plants
High alcohol content
PHARMACEUTICAL APPLICATION:
They are taken orally to relieve a wide range of health
issues like reducing anxiety,relieve pain,etc.
38. Aromatic waters
Aromatic water is also called medicated water, defined in the USP as; clear,
saturated aqueous solutions of volatile oils or other aromatic or volatile
substances.
Concentrated aromatic waters also contain alcohol from 52 – 56 % v/v.
These are to be free from;
Smoke like odor and other odors.
Must have odor and taste similar to those oil or drugs from which they are
prepared.
Preparation of aromatic waters:
There are four important methods which are mainly used;
1. Distillation
2. Solution method
3. Alternative solution method
4. Dilution method
1.Distillation method:
It is the old, the slowest and the most expensive method. Proportion of
drugs in distillate is different in different drugs.
39. Procedure:
Metallic distillation flask or still of proper size/ volume is used.
Solvent should be in suitable volume.
Heating system should also be appropriate.
Placing of drug in the distillation flask should be adjusted so that;
Preparation must be free from Empyreuratic (smoke like) or any
foreign odor.
Partial burning of the drug should be avoided not to develop
carbonized smell.
Filtration for excess of volatile oils through wet filter papers. Moistened oe
wet filter papers provide physical barrier to excess volatile oil not to pass
through.
Example: Stronger rose water is prepared by distillation process.
Note: Redistillation of the distillateis done where the active principle is in
small proportion/ percentage. For example doubled distillated, tirple
distillated or quadruple distillated.
The process is known as Cohobation.
40. 2. Solution method:
Aromatic waters can also be prepared by the repeatedly shaking for 15
minutes. (Certain volume/ amount for e.g. 2ml or 2g of volatile oil/ aromatic
substance with 1000ml of water.)
The resultant solution is set aside at least for 12 hours.
Then filtered off the solution through wet filter paper.
Note:
1. Solid aromatics are comminuted to particles of smaller dimension offering
more surface area for rapid dissolution.
2. Liquid material is shaken well converting into small globules and so
increasing surface area for more contact.
Example: Chloroform water, Camphor water.
3. Alternative solution method:
In this method aromatic water is prepared by thoroughly incorporating about
15g of talc or purified siliceous earth or pulped filter paper into the volatile
oil.
Purified distilled water (1000ml) is added and then whole is agitated for 10
minutes.
41. Then filtered it off through wet filter paper.
Filtering aid is provided to form a layer on filter paper to facilitate filtration.
Note: these incorporated agents are also called “distributing agents.”
Mechanism of distributing agents:
Aromatic substances adsorb onto the surfaces and distributed thoroughly
offering more surface area to dissolve out and so, accelerating the rate of
solution.
Choice of distributing agents:
An effective distributing agent must possess the following characteristics;
It must be insoluble in water.
It must not react chemically with aromatic solute.
Particle size must be appropriately coarse so that filtration is easy and
facilitated.
Note: magnesium carbonate and calcium phosphate were used as
distributing agents but found incompatible as:-
They are inert but slightly soluble.
They react with aromatic solute to give yellowish tint.
Solution becomes alkaline and reacts with the alkaloid to give ppt.
42. 4. Dilution method:
An alcoholic solution of the essential oil is mixed with water and talc. The
mixture is agitated; after several hours it is filtered. The concentrate contains
between 50 and 55 percent alcohol by volume.
One volume of concentrate is diluted with 39 volumes of water, producing
aromatic water which contains less than 1.5 per cent of alcohol.
Example: Concentrated waters of peppermint, dill, cinnamon, and caraway
etc.
Storage of aromatic waters:
Aromatic waters are not permanently stable compounds. These must be
stored in containers having these qualities written below;
Air tight container
Light resistant container
Non- alkaline
Temperature must not be elevated
Contact of aromatic waters with atmospheric air is prevented otherwise
oxidative decomposition or microbial contamination may occur.
Note: Aromatic waters deteriorate with time and therefore, should be made
in small quantities.
43. Advantages:
Aromatic water can be used as viscosity imparting agent for
solutions and also it can musk the bad odor of medicated solution
Disadvantages:
It can alter the pH of the solution which may cause
drug degradation.
44. Uses of aromatic waters:
1) Now days they are not frequently used but they can be used as;
Perfuming, flavoring and for special use i.e. camphor water is used as
vehicle in eye preparations. It gives refreshing and stimulating action.
2) Hamamelis (witch hazel) water is employed in rule a perfuming and
astringent in cosmetics (after shave.)
3) Chloroform water is used as sedative in cough, asthma & colic mixtures.
4) Also as vehicle for administering other ingredients.
46. MACERATION
in the menstruum and the cellular
structure is softened and penetrated
by the menstruum and the soluble
constituents are dissolved.
The usual method is to introduce the
drug into a bottle with menstruum.
Stopper it and agitate it occasionally
for 2 to 14 days. Pour off the liquid,
express the residue to avoid less and
filter the mixed liquid.
47. The word maceration derived from the
Latin word “ macerare ” meaning “ to
soak ”. This process is employed in the
production of a number of preparations
like tinctures, extracts and concentrated
infusions. It is the simplest method of
extraction of crude drugs and was official
in IP 1966. Particle size of drug should be
coarsed or moderately coarse & not fine.
Drug: menstruum ratio should normally
be 1:10. A closed vessel is
recommended, to prevent loss of the
menstruum
48. Types of maceration:
1. Simple maceration (for organized drugs)
2. Maceration with adjustment (for unorganized drugs)
3. Multiple maceration (for concentrated preparations)
4. Circulatory extraction
1. Simple maceration:
It is the most commonly adopted method for the organized drugs. It is also
known as maceration process for tincture from organized drugs. Organized
drugs are those drugs which have specific cell structure like root, stem,
leaves and flowers.
Steps for maceration:
First of all commute the solid crude drug to appropriate size.
Take whole of the menstruum. And add crude drug to the menstruum.
Macerate for 7 days with occasional shaking in a closed vessel.
Press the marc and combined the filterate and expressed liquid.
Combined liquid is allowed to stand so that colloidal particles are settled
down. Decant or filter this combined liquid.
49. The volume is not adjusted in case of organized drugs because when
equilibrium has been attained the potency of the resulting solution will
remain same regardless of the efficiency with which the marc is pressed.
Therefore, these solutions are not adjusted to volume since potency would
then depend on the amount of liquid expressed from the marc e.g. 100g
drug/ 1000ml of menstruum.
Examples:
Tincture of lemon, Tincture of orange etc.
2. Maceration with adjustment:
It is maceration for unorganized drugs. Unorganized drugs are those which
have no specific cellular or tissue structure and are obtained from plants as
their exudates e.g. gums, resins, oleaginous resins etc.
Steps involved:
Take weight amount of drug and powder it.
Then use 4/5th of the menstruum.
Macerate for 2 to 7 days. And shake occasionally.
Perform filtration by filter paper.
50. Marc is not pressed.
Adjust the volume by adding the remaining menstruum through the filter
paper having marc.
Example: Tincture of tolu, tincture of benzoin.
3. Multiple maceration:
Repeated maceration is more important and efficient than simple
maceration because and appropriate amount of active constituents may be
left behind in the first pressing of marc which may be extracted out during
next maceration.
In multiple maceration the total volume of menstruum is divided into parts
and used at different levels instead of whole menstruum. Alcohol is usually
used instead of water because of good penetration due to specific gravity
and moulds can’t grow.
It involves two processes;
a) Double maceration
b) Triple maceration
51. a) Double maceration:
Maceration of drug is carried out twice and total volume of menstruum is
divided into two portions.
In first maceration the weighed amount of drug is allowed to remain in
contact with specified amount of menstruum with occasional shaking for
definite period.
The liquid is then strained and the marc is not pressed.
In 2nd maceration remaining portion of menstruum is added to the marc and
allowed to stand for certain period.
The clear liquid is strained; the marc is pressed and combined the strained
and expressed liquid.
The liquid obtained from 1st and 2nd maceration are combined together, then
filtered and evaporated to get a product of required concentration.
The equation for double maceration is;
Vol. of menstruum for 2nd maceration = total vol. of menstruum – vol. of
mentruum for 1st maceration
52. Procedure:
The whole drug is macerated for 48 hours with the
quantity of menstruum required for first
maceration. Strain the liquid and press the marc.
Macerate again for 24 hours with the remaining
menstruum required for second menstruum.
Strain the liquid and press the marc. Mix the
liquids obtained from the two macerations and
allow it to stand for 14 days and then filter.
Example
Concentrated infusion of Orange Concentrated
Compound infusion of Chirata Concentrated
Compound infusion of Gentian
53. b) Triple maceration:
Menstruum is divided into three portions and maceration is done
thrice.
Weight amount of the drug is allowed to remain in contact with the
one part of menstruum for specified period of time in a closed
container with occasional shaking. Liquid is strained and reserved.
Similarly 2nd and 3rd maceration is carried out .
Marc is pressed at the end of 3rd maceration and expressed liquid is
mixed with liquids obtained from 2nd and 3rd maceration
The liquid from 1st maceration is concentrated than 2nd and 3rd. So,
latter are evaporated and expressed and mixed with 1st maceration.
The equations for triple maceration are;
Vol. of menstruum for 3rd maceration = total vol. of menstruum – vol. used in 1st&
2nd maceration
54. PROCEDURE:
The whole drug is macerated for 1 hour with a part of
menstruum required for 1 st maceration and strained.
Macerate again for 1 hour with a part of menstruum
required for 2nd maceration and strained. Macerate
again for 1 hour with a part of menstruum required for
3rd maceration and strained
Press the marc lightly. then combine the liquids
obtained from 2nd and 3rd macerations and evaporate it
to a specific extent. Mix it with the liquid obtained from
the 1st maceration. Add alcohol 90% equal to 1/4 th of
the volume of the finished product. Adjust volume with
water. Allow it to stand for 14 days and then filter.
EXAMPLE
Concentrated infusion of Quassia
Liquid extract of Senna
55. 4)Circulatory extraction:
The efficiency of extraction in a
maceration process can be
improved by arranging for the
solvent to be continuously
circulated through the drug. as
indicated in the Fig., given below.
Solvent is pumped from the bottom
of the vessel to the inlet where it is
distributed through spray nozzles
over the surface of the drug
56. ADVANTAGES OF MACERATION:
Shorter extraction time
Simplicity of process
Cost effectiveness
DISADVANTAGS OF MACERATION:
Low extraction yield
Lower efficiency
Use of large amount of solvents which
have some health hazards
58. PERCOLATION:
Definition:
It is process in which crude drug is packed into a
column and solvent is allowed to pass through it
till the complete extraction is accomplished
tested by certain tests.
The apparatus used for percolation process is a
percolator. For commercial scale large percolators
are also available.
The word percolation derived from the Greek
word “ percolare ” meaning “ to pass through
”
59. General processes and steps of Percolation:
1. Preparation of the dried crude drug for percolation
a. Powdering
b. Moistening
2. Packing the percolator
3. Period of Maceration
4. Percolation and collection of percolate
5. Adjustment of concentration of percolation as
required
The rates of flow: Percolate slowly – rate will not
exceeding 1 mL of percolate/minute. Percolate at a
moderate rate - rate of 1 to 3mL/minute. Percolate
rapidly – rate of 3 to 5 mL per minute.
60. PRINCIPLE OF PERCOLATOR
Percolation may be defined as ‘ short successive
maceration ’ or ‘ extraction by the method of
displacement.
The powder drug is placed in a cylindrical or
conical vessel called percolator , with a diaphragm
at the base. The menstruum is allowed to pass
through a column of the drug at a regulated rate
which allows the menstruum to dissolve the active
constituents and get saturated. The combined
forces of gravity and that of the column of liquid
above, impel the saturated menstruum downward.
This movement is opposed by the capillarity force.
The physical forces which play an important role
in percolation include; gravitation, viscosity,
adhesion, friction, capillarity, surface tension and
dissolution rate
61. Percolator:
A percolator is a conical vessel having a lid at the top and is provided with a
fake bottom on which cotton wool or filter paper is placed to support the
column of the drug and help in the escape of the percolate. The base of the
percolator is fitted with a tap from which the percolate is collected.
A commercial scale percolator is shown in the diagram having capacity of
about one ton.
Types of percolator:
Selection of the percolator depends upon the nature and cost of the solvent
used for the percolation. The various types of percolators are mentioned
below;
Open percolator
Closed percolator
Steam jacket percolator
Types of percolation
Percolation can be performed by these three methods which are mentioned
below;
1) Simple percolation 2) Reserved percolation
3) Continuous extraction or percolation
62. 1)SIMPLE PERCOLATOR:
Apparatus:
Three types of apparatus are generally used, i) Conical
percolator ii) Cylindrical percolator iii) Steam jacketed
percolator [for higher temperature extraction]
It is one of important process of extraction in which drug
is moistened with menstruum sufficiently & packed in
conical percolator, excesses of menstruum is poured
over the drug and allowed to pass through or percolate
for 24 hrs, marc is pressed , filtered.
Eg:- Tincture of belladonna, compound tincture of
cardamom, strong tincture of ginger, liquid extract of
nux vomica , liquid extract of cascara sagrdas.
63. 1. Simple percolation:
a) Size reduction: It is carried out;
To increase the surface area of the drug substance.
For the uniform packing of the drug.
To slow down the movement of menstruum across the crude drug.
Also, to ensure the complete exudation of the crude drug.
b) Imbibition or moistening of crude drug:
It is done with a suitable solvent and allowed to stand for 4 hours in closed
container.
The drug will swells up and the menstruum will get into the cell wall of the
crude drug.
After a lapse of time the drug is poured through a coarse scene to remove any
lumps and to mix the dry powder.
Preliminary moistening is essential to avoid chocking of percolator, and
washing of fime particles put of percolator.
c) Packing:
After imbibition the imbibe drug is evenly packed into the percolator.
64. d) Maceration:
After packing of the crude drug sufficient amount of the menstruum is
added to saturate the material and close the percolator with a lid.
Maintain the large of menstrum over it for uniform and continuous
percolation.
Macerate the crude drug for 24 hours.
e) Percolation:
After 24 hours, the tap of the percolator is opened and collected liquid is
allowed to drip down at a controlled speed till 3/4 volume is collected.
More menstruum is added so that marc does not become dry.
Percolate is tested for complete exhaustion of drug.
The marc is pressed and the expressed liquid is allowed to the already
collected percolate.
The liquid is allowed to stand to settle the suspended percolates, then
decanted and clarified.
f) Tests:
Take few ml of last percolate and evaporate to dryness, if no residue
remains then drug is completely exhausted.
65. Measure the specific gravity of the last few ml of the percolate, if it equals
to the specific gravity of the menstruum used, then the drug is exhausted.
Specific tests may be performed on percolate containing alkaloids,
glycosides, tannins, resins etc.
2. Reserved percolation:
1st portion (about 3/4 of the final product) of the percolate containing
maximum active principles is reserved.
Subsequent percolation is completed until drug is exhausted but the last
1/4th of final volume is collected separately.
2nd dilute part is evaporated to get the syrupy consistency which is then
mixed with reserved portion and final volume is adjusted with
menstruum.
Reserved percolation is used for preparation of liquid extracts which are
more concentrated preparations as compared to tinctures prepared by
simple percolation process.
Generally alcohol is used as menstruum.
Not all percolate is subjected to heat treatment for evaporation.
Examples: liquid extract of liquorice.
66. 3. Continuous extraction:
The process is used:
When penetration power of menstruum into cellular structure is very low.
Solute is not readily soluble in the solvent.
Quantities of menstruum are very less.
In this process;
In normal extraction process, concentrated preparations are made
followed by evaporation of solvent.
Continuous extraction combines two operations i.e. evaporation and
condensation.
Condensed liquid is returned to the drug to continue extraction.
So with the help of temperature smaller volumes of solvent may be used
and process is called “continuous extraction.”
Some volume of the solvent is used again and again using special apparatus.
A continuous extraction may be;
1) Continuous hot extraction
2) Continuous cold extraction
In both of the above mentioned extraction process the principle of
‘distillation’ is exploited.
67. ADVANTAGES OF PERCOLATION:
Percolation is more efficient than
maceration because it is a continuous process in
which the saturated solvent is constantly being
replaced by fresh solvent.
It is applicable to a wide range of medicinal
materials. Components that are unstable under
thermal conditions can be effectively extracted
DISADVANTAGES OF PERCOLATION:
High solvent consumption
Long extraction time
High energy consumption in subsequent
concentration processes.
68. Liquid-liquid extraction (counter current extraction):
It is a process of separating organic substances from aqueous solution e.g.
alkaloids.
Principle: It is based on the principle of partition coefficient of drug between
two solvents.
Important components:
1) Higher is the partition coefficient greater will the extraction of desired
substance.
2) Distribution between the water and organic solvent depends upon the
hydrophilic and hydrophobic group of drugs.
3) If hydrophilic group is ionizable, then pH plays an important role.
4) If the ionization constant is high then separation of isomers can be
accomplished.
5) Decrease in interfacial tension will increase liquid-liquid extraction due to
more interfacial area.
6) Impurities present between the two immiscible liquids may retard as the
migration of drug. (This problem of impurities can be overcome by the
addition of short chain alcohols (C6) which replace the impurities.)
7) Removal of impurities increases separation of drugs.
69. Applications:
Separation of ‘Bacitracin’ in butanol from bacterial growth medium.
Purification of antibiotics.
Example:
Extraction of alkaloids: Counter current extraction is based on the
principle of partition coefficient principle. Let’s understand the phenomenon
by the example by the extraction of an alkaloid. In water chloroform
combination, the drug is partitioned on the same principle.
Chloroform & water solvent:
1) Equal volume of chloroform is added to each three tube.
2) Drug dissolved in water is added to the tube 1.
3) Tube shaken to achieve equilibrium settled, and the upper aqueous layer
to tube 2.
4) Equal volume of aqueous layer added to tube 1 and 2.
5) Tube 1 and 2 shaken and settled down aqueous phase to tube 2 and 3.
