Extraction
Vikrant Saluja
Faculty of Pharmaceutical Sciences
PCTE Group of Institutes, Ludhiana
Punjab, India
Extraction involves the separation of medicinally
active portions of plant or animal tissues from the
inactive components through the use of selective
solvents
The extracted preparation are known as Galenicals
A medicinal preparation composed mainly of
herbal or vegetable matter prepared by extraction of
crude vegetable drugs (active principles) with
suitable solvent(s).
Menstrum: Solvent used for extraction (ex. water,
alcohol, ether)
Marc: The inert fibrous and other insoluble materials
remaining after extraction
Extracts are preparations of liquid (liquid extracts and tinctures), semi-solid (soft
extracts) or solid (dry extracts) consistency, obtained from herbal drugs or animal
matter
LIQUID EXTRACTS :
• Liquid extracts are liquid preparations of which, in general, 1 part by mass
or volume is equivalent to 1 part by mass of the dried herbal drug or
animal matter.
• Liquid extracts are prepared by using ethanol of a suitable concentration or
water to extract the herbal drug or animal matter, or by dissolving a soft or dry
extract of the herbal drug or animal matter in either ethanol of a suitable
concentration or water.
TINCTURES:
• Tinctures are liquid preparations that are usually obtained using either 1 part
of herbal drug or animal matter and 10 parts of extraction solvent, or 1
part of herbal drug or animal matter and 5 parts of extraction solvent.
• Tinctures are prepared by maceration or percolation using only ethanol of a
suitable concentration for extraction of the herbal drug or animal matter, or by
dissolving a soft or dry extract of the herbal drug or animal matter in ethanol of
a suitable concentration.
SOFT EXTRACTS
• Soft extracts are semi-solid preparations obtained by evaporation or
partial evaporation of the solvent used for extraction.
DRY EXTRACTS
• Dry extracts are solid preparations obtained by evaporation of the
solvent used for their production.
• Dry extracts usually have a water content of not greater than
5 per cent .
General method of Extraction:
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 filtration or expression.
Choice of menstrum
The ideal solvent for a certain pharmacologically active
constituent should:
1. Be highly selective for the compound to be extracted.
2. Have a high capacity for extraction.
3. Not react with the extracted compound or with other
compounds in the plant material.
4. Have a low price.
5. Be harmless to man and to the environment.
6. Be completely volatile.
The generally used solvents includes:
Water
Aliphatic alcohols with up to three carbon atoms
Ether
Chloroform
Glycerine
Water Alcohol
Advantages: Advantages:
Cheap Selective
Non toxic No additional preservative is required (>20%)
Non inflammable Non toxic
Disadvantages: Disadvantages:
Non selective Costly
Promote hydrolysis
Promote enzymatic degration
Good media for microbial growth
Solvent of choice for: Solvent of choice for:
Proteins Alkaloids
Colouring matter Alkalodal salts
Gums Glycosides
Alkalodal salts Volatile oils
Glycosides Tannins
Sugars Resins
Enzymes
Anthraquinone derivatives
Organic derivatives
Infusion
Infusions are dilute solutions containing the readily soluble
constituents of crude drugs.
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
• 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 drug 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.
• The perforated tray or muslin bag confers two advantages:
A- Complete extraction because when the menstrum surrounding the drug
becomes saturated, it will sinks to the bottom due to its increased density and another
amount of fresh menstrum displace it leading to circulatory diffusion
B- At the end of infusion time, the drug can be lifted out, leaving clear liquid
which can be strained quickly.
Fresh (Dilute) Infusion
• A fresh infusion is an aqueous solution of active constituents of a vegetable drug
prepared by the process of infusion.
• Water is used as menstrum
• Fresh infusion should be used within 12 hrs after its preparation because it gets
spoiled due to bacterial and fungal growth.
• eg. Fresh infusion of Quassia
Concentrated (stock) infusion
• Prepared by double or triple maceration
• 8 times stronger than fresh infusion
• Alcohol in the concentration of 20-25% is used as menstrum.
• Avoid rapid decomposition to which the fresh (dilute) infusions are subjected.
• The dilution of 1 volume of concentrated infusion with 7 volumes of water
resembles corresponding fresh infusion in potency.
• eg. Concentrated infusion of Quassia
Decoction
• In this process, the crude drug is boiled in a specified volume of water
for a defined time (10 mins ); 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
Comparison between infusion and decoction
Infusion Decoction
1- Plant Soft structure (ex. Senna Hard woody structure (ex.
leaves) Cinchona bark)
2- Menstrum Boiling or cold water Boiling water
3- Procedure Infusing the drug with cold or Boiling the drug with water
hot water
4- Time Calculated as soon as water is Calculated as soon as the
added to drug water begins to boil
5- Adjustment of No adjustment Adjustment is necessary
final volume
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
Digestion
In this process the plant cells are subjected to the effect of menstrum
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
Maceration:
Term derived from latin word “macerare”
meaning to soak.
Process in which the properly comminuted drug
is permitted to soak in the menstruum and the
soluble constituents are dissolved
Officially, maceration is used for
a) Tinctures made from organized drugs.
b) Tinctures made from unorganized drugs.
c) Concentrated preparation, involving double
and triple maceration.
Organized drugs Unorganized drugs
Drug +Entire volume of menstrum Drug + 4/5 of menstrum
Shake occasionally for 7 days. Shake occasionally on days 2-7
Strain Liquid and press the marc Decant liquid. Marc is not pressed
Mix the liquids and clarify by filtration. Filter the liquid and final volume is
Final volume is not adjusted adjusted by remaining menstrum
Eg. Vinegar of squill Compound tincture of benzoin
Oxymel of squill Tincture of Myrrh
Tincture of orange Tincture of Tolu
Tincture of lemon
Tincture of squill
Multiple Maceration
Same as simple maceration process but the menstrum is
divided into parts (two for double and three for triple).
Double maceration
Drug is macerated twice
Menstrum is divided in to two equal parts
Volume of menstrum required for first maceration
Total vol. of menstrum- vol. to be retained by the drug
+ vol. to be retained by the drug
2
Volume of menstrum required for second maceration
Total vol. of menstrum- vol. of menstrum used for first maceration
Drug is macerated for 48hrs
(with the quantity of menstrum required for 1st maceration)
Strain the liquid and press the marc
Macerate again for 24 hrs
(with remaining menstrum required for 2nd maceration)
Strain the liquid and press the marc
Mixed the liquid obtained from the two maceration
Allow it to stand for 14 days and then filter
Percolation
Simple percolation – for
tinctures
Eg. Tincture of Belladona
Strong tincture of Ginger
Reserve process - for
concentrated preparation.
Continous hot percolation
or Soxhelation.
Percolation (Exhaustive Extraction)
Process
A preliminary uniform moistening of the raw material with the menstruum for a period of 4 h
in a separate closed vessel; this process is called imbibition.
After imbibition, the drug is packed evenly into the percolator.
Sufficient menstruum is now poured over the drug slowly and evenly to saturate it, keeping the
tap at the bottom open to allow the occluded gases between particles to pass out.
When the menstruum begins to drip through the tap, the tap is closed; sufficient menstruum is
added to maintain a small layer above the drug and allowed to stand for 24 h.
The 24-h maceration period allows the solvent to diffuse through the drug, solubilize the
constituents and leach out the soluble material.
After the maceration, the outlet is opened and the solvent is percolated at a controlled rate
with continuous addition of fresh solvent.
About 75% of the volume of the finished product is collected. The marc is pressed and the
expressed liquid is added to the percolate, giving about 80%-90% of the final volume
,. Modifications of the General Process of Percolation
In general process of percolation, particularly in the manufacture of
concentrated preparations like liquid extracts, the following problems
may arise:
a) If the active substances are thermo-labile, evaporation of large
volume of dilute percolate, may result in partial loss of the active
constituents.
b) In the case of alcohol- water mixture, evaporation results in
preferential vaporization of alcohol leaving behind an almost aqueous
concentrate which may not be able to retain the extracted matter in
solution and hence get precipitated.
In such cases the modification in general process of percolation is
required as given below:
Reserved Percolation
Reserved Percolation
In this case , a part of the percolate , generally ¾ th the volume of
finished preparation is reserved . Then the percolation is continued till
the drug is completely exhausted.
At the last, the evaporation is done under reduced pressure in
equipment like a Climbing evaporator to the consistency of a soft extract
(semi solid) such that all the water is removed.
This is then dissolved in the reserved portion which is strongly
alcoholic and easily dissolves the evaporated portion with any risk of
precipitation.
Continuous hot percolation process or Soxhlet extraction
Apparatus
The apparatus consists of
A flask
A soxhlet extractor
A reflux condenser
A side tube
A syphon tube
Process
The raw material is usually placed in a thimble made of filter paper and inserted
into the wide central tube of the extractor.
Solvent is placed in the flask and brought to its boiling point.
Its vapour passes up the larger right hand tube into the upper part of the drug and
then to the condenser where it condenses and drops back on to the drug.
During its percolation, it extracts the soluble constituents.
When the level of the extracts reaches the top level of syphon tube, the whole of the
percolates syphon over into the flask.
The process is continued until the drug is completely extracted and the extract in the
flask is then processed.
This extraction is series of short maceration.
