EXTRACTION PROCESS

1. SEPARATION TECHNIQUES

Different techniques are used for the separation of solid – liquid and liquid – liquid
components using physical and chemical methods dependent on the phases of the
substance involved and the amount of material present. These methods include;

1. Extraction
2. Distillation.
3. Filtration.
4. Precipitation.
5. Crystallization.
6. Centrifugation.

1.1 IMPORTANT TERMINOLOGIES USED IN EXTRACTION PROCESS

1. Menstrum.
2. Marc
3. Communition
4. Expression.
5. Soxhlet.
6. Thimble
7. Extractant
8. Extragent
9. Contusion or bruising.
10. Grinding
11.Tinctures
12.Fluid extract
1. Menstrum. The selective solvent or combination of solvents used in the
extraction process is known as menstrum.
2. Marc: The residue left behind after the extraction of desired constituents is
called Marc or The inert fibrous and other insoluble materials remaining after
extraction.
3. Communition. Comminution is a general term for various processes used to
reduce the size of crude drug material.
4. Expression. The Separation of the menstrum containing the dissolved active
pharmaceutical ingredients from the marc after extraction process by applying
force or squeezing and filtration. OR Expression. is the physical act of
applying pressure to squeeze out oils or juices from plants. This was normally
achieved with a tincture press.
5. Soxhlet. The hot continuous extraction is called soxhlet.
6. Thimble. The strong filter or porous bag used to place or retain the finely
grounded crude drug placed in the Soxhlet apparatus is called thimble.
7. Extractant. The selected solvent after heating and its vapors after condensing
and drips or pass into the thimble (circulated) containing the crude drug.
8. Extragent is the term used for organic solvent (menstrum) used for
extraction of medicinally active constituents.The density of extragent must be
differ from water and should have minimum viscosity than water.
9. Contusion or bruising is the process of reducing a drug to small particles but
not to fine powder by striking it with several times.
10.Grinding is the general term used to reduce a substance to a fine powder.
11.Tincture is the alcoholic or hydro alcohol solution achieved by extraction
process of vegetable part or chemical substances (simples solution method)
with alcohol (15% to 80%) or hydro alcohol menstrum. Example of
pharmaceutical tincture by extraction method are compound benzoin tincture,
 vanilla tincture, belladonna tincture, sweet orange peel tincture etc where as
examples of simple solution method includes Iodine tincture, Themirosal
tincture.
12. Fluid extract is the Pharmacopeial liquid preparation (extract) of plant or
vegetable drugs, made by percolation that contains alcohol as a solvent or
preservative or both. The fluid extract of each mL contains therapeutic
constituents (medicinal activity) of one gram of standard crude drug (powder)
form) that it represents.
 2. Extraction process?

“Extraction is the separation technique that involves the separation of medicinally

active portions of plant or animal tissues from the inactive components through the
use of selective solvents through selective method”

2.1 So Question arises? What is the sole purpose of extraction in pharmaceutical

field?

The sole purpose of extraction process in pharmaceutical field is to;

1. To obtained, separate and isolate the desired single pure molecule which is
therapeutically active from the crude drug and eliminate the inert or
undesired material (Marc) by treatment with a selective solvent (Menstrum)
2. To check and analyze the qualitative and quantitative composition of the
various components of extracts.
3. To isolation and characterization of therapeutically active chemical
constituents in modern medicine.

2.2. Stages of medicinal herbs before Extraction:

1) Sorting of crude drug and removal of dirt and weeds(unwanted plants)
2) Drying
3) Crumbling up
4) Sifting
5) Selection of optimum extragent or menstrum
6) Choice of extraction method and technique.
3.0. Classification of Extraction
Extraction process is selected on basis of the nature of a crude drug and drug
extracted from the raw and unprocessed drug i-e heat labile and heat stable
component of the drug and menstrum used during the extraction process.
The extraction process is mainly divided into three types which are;
3.1. Periodical extraction.
3.2. Continuous extraction.
3.3. Countercurrent extraction.

3.1. Periodical extraction.

This type of extraction process is used on small scale/ laboratory scale
mostly for the research purpose. In this process glass separator or separating
funnel. The menstrum/ extragent and crude drug is shaking vigorously and
extracted active constituent and marc is separated and filtered. On small
scale or laboratory scale if large amount of multiple extraction or separation
of Extragent and aqueous extractant need to separate so continuous or
Rotary evaporator is used as shown in the figure.
3.2. Continuous extraction.
In continuous extraction the crude drug is loaded and the menstrum is
poured on the top of the container. The menstrum or extragent is
continuously added at the top of the container and collected at the lower tap.
The addition of menstrum is controlled by the tap of the container where the
extract is collected.
All the quantity of extractant is collected, separated and dried.
3.3. Countercurrent extraction
The countercurrent extraction process is done on both small scale and large
scale. On small scale or laboratory scale, the countercurrent extraction is
done in a special type apparatus called the soxhlet apparatus as shown in
the figure below. The apparatus is made up of glass as shown in the figure
below. on large scale production, when large amount extraction of active
pharmaceutical ingredient (API) of medicinal herbs need to processed so
mostly the countercurrent extraction is preferable.
In this method a closed system containing a number of stainless steel
vessels is interconnected through pipes in which the menstrum is circulating.
This process is also called extraction battery. The menstrum is showered
from the top of the vessel, passing from the crude drug and transfer from
bottom to the next vessel by using transfer pumps. This method is used to
get maximum concentrate either in the form of fluid extracts, tinctures,
pilular (resemble to pills) extracts and powdered extracts which are
collectively called galenicals.
3.3.1. Procedure countercurrent extraction
When the efficiency of extraction in a maceration or percolation process not
satisfied or time consuming so the countercurrent extraction process is
preferable.
 In this technique the vessels are arranged in such a manner that solvent can
be added to and the product can be taken from any vessel.
In this method the extraction process is improved by arranging the vessels,
the solvent is continuously circulated through the crud drug.
In multiple stage extraction, the menstrum is distributed through spray
nozzles over the surface of the drug from the top of the first vessel and
pumped from the bottom of the vessel to the inlet of the second vessel and so
on. Repeat the cycle by collecting the extractant from the last vessel to the
first vessel and circulating continuously until the required concentrate is
achieved.
3.3.2. Question Why countercurrent extraction is required?
In the normal percolation or maceration process when the percolate is not of
maximum concentration so continuous extraction devices of this type are used to
get the maximum concentrate in a short time of period.
4.0. Methods of Extraction
1. Maceration
2. Percolation
3. Infusion
4. Decoction
5. Digestion
6. Extraction battery or large scale extraction (Circulating or continuous
extraction)
 4.1. MACERATION
Maceration is the simplest method of extraction. In this method, the definite
quantity of properly communited, crushed or cut small or moderately coarse
powder of crude drug of plant is placed or soak in a menstrum for specified
period of time usually for the period of three days or until the crude cellular
structure is softened by absorbing the menstrum in a closed vessel at room
temperature. The soluble constituents are dissolved and extracted out.
The maceration process is divided into;
i. Simple maceration process
ii. Multiple Maceration process.

i) Simple maceration process

In this method the whole menstrum is added to the communited crude
drug of plant is placed or soak in a closed container or vessel and shaking
occasionally for seven (7) days. The solid residue (Marc) and menstrum
is pressed and separated and recovers the extractant by filtration,
evaporated and concentrated. Example of maceration includes Tincture of
orange, Tincture of lemon, Tincture of Squill, Compound tincture of
benzoin, Tincture of Myrrh, Tincture of Tolu.

ii) Multiple Maceration process.

In this method the menstrum is divided into parts or three parts. In double
maceration, the menstrum is divided into two equal parts and the drug is
macerated twice.
4.1.1. Procedure: In multiple or double maceration process the drug is
macerated for 48hrs with the quantity of menstrum required for 1st maceration.
Strain the liquid and press the marc. The marc is macerated again for 48hrs with
remaining menstrum Strain the liquid and press the marc. Mixed the liquid
obtained from two maceration. Allow it to stand for 14 days and then filter.
4.2. PERCOLATION

Percolation is an extraction method mostly used to extract active ingredients in the

preparation of tinctures and fluid extracts. The percolation is done in a narrow,
cone-shaped vessel open at both ends called percolator.

In this method the crude drug is packed in a percolator in a well-disciplined

manner and moistened with an appropriate amount of menstrum. The top of the
percolator is closed and allowed to stand for approximately 4 hours. An additional
menstrum is added to form a shallow layer above the mass. The mixture is allowed
to macerate in the closed percolator for 24 h. The outlet of the percolator at the
bottom is opened and the extract is allowed to drip slowly.

Additional menstrum is added as required, until the percolate measures about

three-quarters of the required volume of the finished product. The marc is then
expressed and the liquid containing menstrum and extract is added to the percolate
and sufficient menstrum is added to produce the required volume.The mixed liquid
containing menstrum and extract is clarified by filtration or by standing followed
by sedimentation or decanting.
4.3. INFUSION.

Infusions are dilute solutions containing the readily-soluble constituents of crude

drugs. Formerly the fresh infusions were prepared and used by macerating the drug
for a short period in cold water or boiling water.

Now, infusions are usually prepared by diluting one volume of a concentrated

infusion to ten volumes with water. Concentrated infusions are prepared by
modified percolation or maceration process, which after dilution with water,
resemble in potency and aroma the corresponding fresh infusion. Infusions are
liable to fungus and bacterial growth, and it is necessary to dispense them freshly
or within twelve hours of their preparation.

4.3.1. General method for preparing fresh infusion

The following are the steps for the preparation of infusion

1. The drug is usually coarsely powdered, very fine powder being avoided (50
gm).
2. Moisten the drug in a suitable vessel, provided with a cover, with 50 ml of cold
water.
3. Allow to stand for 15 minutes.
4. Then add 900 ml of boiling water, cover the vessel tightly.
5. Allow it to stand for 30 minutes.
6. Then strain the mixture, pass enough water to make the infusion measure 1000
ml
7. Some drugs are supplied in accurately weighed in muslin bags for preparing
specific amounts of infusion.
8. If the activity of the infusion is affected by the temperature of boiling water,
cold water should be used.
9. As the fresh infusions do not keep well, they should be made
extemporaneously and in small quantities.
4.3.2. Preparation of Concentrated Infusions
1. The official monographs also recognize certain “concentrated infusions” in
which 25% alcohol is added during or subsequent to the infusion process.
2. Concentrated infusions are especially prepared in which the active and
desirable principles of drug are equally soluble in water or in the menstruum
used for both concentrate and infusions.

4.4. DECOCTION

In this process, the crude drug is boiled in a specified volume of water for a
defined time; it is then cooled and strained or filtered. This procedure is suitable
for extracting water-soluble, heat stable constituents.

This process is typically used in preparation of various extracts, galenicals, fluid

extracts etc. 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.

4.5. DIGESTION

This is a form of maceration in which gentle heat is used during the process of
extraction. It is used when moderately elevated temperature is not
objectionable. The solvent efficiency of the menstrum is thereby increased.
5.0 FACTORS AFFECTING CHOICE OF EXTRACTION PROCESS

The final choice of the process to be used for the extraction of a drug will depend
on a number of factors, including:

5.1. Character of Drug

1. If hard and tough (such as nux vomica) use percolation.
2. If soft and parenchymatous (such as gentian) use maceration.
3. If ‘unpowderable’ (such as squill) use maceration.
4. If an ‘unorganized drug (such as benzoin) use maceration.
5. If preferable to avoid powdering (such as senna fruits) use maceration.

5.2. Therapeutic value of the drug

When the drug has considerable therapeutic value, the maximum extraction is
required, so that percolation is used, as in belladonna. If the drug has little
therapeutic value, however, the efficiency of extraction is unimportant and
maceration is adequate; for example, “flavours” (lemon), or “bitters”, (gentian).

5.3. Stability of drug

Continuous extraction should be avoided when the constituents of the drug are
thermo-labile.

5.4. Cost of drug

From the economic point of view, it is desirable to obtain complete extraction of an

expensive drug, so that percolation should be used; Ginger is an example of this
type.
For cheap drugs, the reduced efficiency of maceration is acceptable in view of the
lower cost of the process. In particular, the cost of size reduction to a powdered
state is avoided, whereas this is a significant part of the percolation process.

5.5. Choice of Solvent

If the desired constituents demand a solvent other than a pure boiling solvent or an
azeotrope, continuous extraction should be used.

5.6. Recovery of solvent from the marc

The residue of the drug after extraction (often known as the marc) is saturated with
solvent and if economic the latter is recovered.
 Assignment of Extraction process

Question1. Define and classify various types of extraction?

Question 2. Enlist and Describe each method of extraction process?

Question3. Differentiate between Maceration and percolation method of

extraction?

Question 4. Write short, summarize and precise method of soxhlet extraction?

Question5. What is meant by extraction battery and why we prefer extraction

battery over the conventional extraction methods?

Question6. Why countercurrent extraction is required?

In the normal percolation or maceration process when the percolate is not of

maximum concentration so continuous extraction devices of this type are used to
get the maximum concentrate in a short time of period.

Question 7 Why we need fractionating extract or fluid extract using separation

techniques and apparatus such as separating funnel, fractional distillation or rotary
evaporators?

Answers; The extract obtained may be ready for use as a medicinal agent in the
form of tinctures and fluid extracts, but if needed to further processed to be
incorporated in any dosage form such as tablets or capsules, or may fractionated to
isolate individual chemical entities(API) which are more potent so these modern
techniques are used.

Question 8 What is the sole purpose of extraction in pharmaceutical field?

The sole purpose of extraction process in pharmaceutical field is to;

1. To obtained, separate and isolate the desired single pure molecule which is
therapeutically active from the crude drug and eliminate the inert or
undesired material (Marc) by treatment with a selective solvent (Menstrum)
2. To check and analyze the qualitative and quantitative composition of the
various components of extracts.
3. To isolation and characterization of therapeutically active chemical
constituents in modern medicine.
Q. No Questions
1 Define and classify various types of extraction?
2 Enlist and Describe each method of extraction process?
3
Differentiate between Maceration and percolation method of extraction?
4 Write short, summarize and precise method of soxhlet extraction?
5
What is meant by extraction battery and why we prefer extraction battery
over the conventional extraction methods?

6 Why countercurrent extraction is required?

7 Why we need fractionating extract or fluid extract using separation
techniques and apparatus such as separating funnel, fractional distillation or
rotary evaporators?
8 What is the sole purpose of extraction in pharmaceutical field?