Modern method of extraction
EXTRACTION: Modern method of Extraction is the method of removing active constituents from a soild or liquid by means of liquid solvent is called extraction.
Extraction is defined as the process of isolation of soluble material from an insoluble residue, which may be liquid or solid, by treatment with a solvent, the crude drug contain the active constituents which can be isolated from these drugs by various methods of extraction and separation.
EXTRACT: Extract can be defined as preparation of crude drugs which contain all the constituents which are soluble in the solvent.
Marc: Solid residue obtain after extraction.
Menstrum: Solvent used for extraction.
Types Of Extract in modern method of extraction
Dry extract – Tablet, Capsules (E.g. belladonna extract).
Soft extract – Ointment, Suppository (E.g. glycyrrhizin extract).
Liquid extract – As tincture.
Extraction process is controlled by mass transfer.
Mass transfer is defined as a unit operation Which involves the transfer of mass of soluble material from a solid to a fluid.
If a crude drug Particle is immersed in a solvent to be used for extraction, the particle is surrounded by a Boundary layer of the solute, the solvent starts penetrating inside the particle and Subsequently forms solution of the constituents within the cells.
Escape of this dissolved Constituent through the cell wall and through the boundary layer takes place. The process is Continued till equilibrium is set up between the solution in the cells and the free solution.
Extraction process is dependent on the selection of the method of extraction and the solvent Selected for extraction.
modern method of Extraction methods are classified in to two categories.
1 Small scale extraction processes are;
This process is generally slow and time consuming and also gives the insufficient extraction of the crude drugs.
2 Large scale extraction process is modified soxhlet extractor.
Large batches of drug materials are extracted easily with the help of attachments.
Types of Modern Method of extraction
- Continues hot extraction
- Supercritical fluid extraction
- Counter current extraction
- Microwave assisted extraction
- Ultra sonication-Assisted Extractions.
MACERATION-Modern method of extraction
Maceration process involves the separation of medicinally active portions of the crude drugs.
It is based on the immersion on the crude drugs in a bulk of the solvent or menstrum.
Stoppered container is filled with solid drug material with about 750 ml of the menstrum and allowed to stand for at least three to seven days in a warm place with frequent shaking, the mixture of crude drug containing solvent is filtered until most of the liquid drained off.
The filtrate and the washing are combined to produce 1000 ml of the Solution.
Maceration method is modified to multiple stage extraction to increase the yield of the active Ingredients in the extracts.
The crude drug material is charged in the extractor which is connected with a circulatory pump and spray distributor, along with number of connected tanks to receive the extraction solution.
This is known as multiple stage extraction because the solvent added and circulated in the extractor containing drug is removed as extracted solution and is stored in the receiver tanks.
This operation is repeated thrice.
When the fresh drug material is charged in the extractions the stored solution is once again circulated through fresh drug and then removed as an extract.
Likewise after three extractions the drug is removed from the extractor.
Again recharged with fresh drug and the whole cycle is repeated.
PERCOLATION-Modern method of extraction
Percolation is a continuous flow of the solvent through the bed of the crude drug material to get the extract.
First step of the process powdered drug is treated with sufficient menstrum to make it uniformly wet.
Damp material is allowed to stand for about 15 minutes and then transferred to a percolator which is generally a “V’ shaped vessel open at both ends.
Sufficient menstrum is added to saturate the drug. The lid placed on the top.
The liquid starts dripping out from the outlet of the percolator, the lower opening is closed.
The drug material is allowed to macerate in the vessel for 24 hours and then percolation is continued gradually using sufficient menstrum to produce 1000 m1 of solution.
The process is dependent upon the flow of solvent through the powdered drug and it yields the products of greater concentration than the macerated products.
Steps in percolation:
In modern method of extraction percolation involves Following steps;
Size reduction: The drug to be extracted is subjected to suitable degree of size reduction, usually from coarse powder to fine powder.
Imbibition: During imbibition the powdered drug is moistened with a suitable amount of menstrum and allowed to stand for four hours in a well closed container.
Packing: After imbibition the moistened drug is evenly packed into the percolator.
Maceration: After packing sufficient menstrum is added to saturate the material. The percolator is allowed to stand for 24 hours to macerate the drug.
Percolation: The lower tap is opened and liquid collected there in is allowed to drip slowly at a controlled rate until 3/4th volume of the finished product is obtained.
The conventional percolation process is modified to include evaporation for the production of more concentrated products especially when solvent id dilute alcohol.
The strength of the alcohol needs to be unaffected by concentration of the extract, percolation is continued and the first quantity of the percolate is collected and set aside.
The subsequent quantities of the percolates are collected, concentrated and the first volume of the percolate is added in the final product.
In this way it maintain the required alcohol strength and also produces the higher concentration of the products. The process is known as reserve percolate method.
In modified process of percolation technique continuous or semi continuous extraction devices are used in some industries for handling the batches of varying size.
The extraction battery which consist of a number of vessels in series are interconnected through pipelines and arranged in such a way that the solvent can be added.
The product removed from any vessel such type of extraction battery gives maximum efficiency of extraction with minimum use of solvent.
The product obtained is more concentrated and less losses of solvent takes place due to evaporation.
soxhlet apparatus: Soxhlet extraction is the process of continuous modern method of extraction in which the Same solvent can be circulated through the extractor for several times.
This process involves extraction followed by evaporation of the solvent. The vapours of the solvent are taken to a condenser and the condensed liquid is returned to the drug for continuous extraction.
Soxhlet apparatus designed for continuous extraction process. It consists of Body of extractor attached with side tube and siphon tube.
The extractor from the lower side can be attached to distillation flask
Mouth of the extractor is fixed to a condenser by the standard joints.
In modern method of extraction the crude drug powder is packed in the Soxhlet apparatus directly or in a thimble of
Filter paper or fine muslin.
The diameter of the thimble corresponds to the internal diameter of the soxhlet extractor.
Extraction assembly is set up by fixing condenser and a distillation flask.
Powder packing is completed, solvent is allowed to siphon once before heating. Fresh
Activated porcelain pieces are added to the flask to avoid bumping of solvent.
The vapours pass through the side tube and the condensed liquid gradually increases
The Level of liquid in the extractor and in the siphon tube.
A Siphon is set up as the liquid reaches the point of return and the contents of the
Extraction chamber are transferred to the flask.
The cycle of solvent evaporation and siphoning back can be continued as many times as possible without changing the solvent, so as to get efficient extraction.
This method although a continuous extraction process, is nothing but a series of short
Less amount of solvent is needed, for yielding more concentrated products.
Extraction can be continued until complete exhaustion of the drug.
Process is restricted to pure boiling solvents to azeotropes.
LARGE SCALE EXTRACTION
Large scale extraction is meant for the extra-large batches of drug material, the various
Assemblies which are generally in attachment with the body of soxhlet extractor are
The pilot plant extractor, generally have a separate extractor and condenser unit.
Separate inlet for loading the drug and an outlet for drug discharge are provided.
The extractor body is divided into two parts, the upper one of the drug material and the lower
One as a distillation chamber. The distillation chamber is electrically heated. The vapours of
The solvent are passed to condenser and the condensed liquid is sprayed on the bed of crude
Drug with the help of solvent distribution nozzle. Such large scale extractors are provided
With the outlet from the lower side of the extractor, for removing the extract. The following
Figure shows pilot plant extractor.
SUPER CRITICAL FLUID EXTRACTOR
It is a recent method of extraction of drugs. Certain gases behave like a free flowing liquids
Or supercritical fluids at the critical point of temperature and pressure. Such supercritical
Fluids have a very high penetration powers and extraction efficiency.
This principle was first in the food packing industries for the deodorization of the packed food products. The gases like CO2 are held as a supercritical fluid at the critical point 73.83 bar pressure and 31.06 C temperature. At this critical point CO2 behave as a liquefied gas or free flowing and Assists the extraction of the phytochemical constituents from the crude drugs.
The following phase diagram of CO2 indicates the characteristic areas for the deodorization, extraction and fractionation.
Carbon dioxide used in super critical fluid extraction has the following advantages;
Sterile and bacteriostatic
Non-combustible and non-explosive
Carbon dioxide is harmless to environment and no waste products are generated during
The process and it is available in large amount under favourable condition.
The mixture to be fractionated in passed in the extraction column along the length of which
The heater is located. Carbon dioxide is purged through the column. Once the extraction is
Pressurized, drug material gets saturated in the supercritical fluid which moves along the
Length of the column. The operating conditions, i.e. pressure and temperature are selected.
In the pressure controlled type of extraction, the solution is just expanded in the separation
Stage to precipitate the extract and then again the gas is recompressed for recycle. In
Temperature control type operation, the extract is precipitated by heating the solution which
Lowers the solvent density. The density is then increased by isobaric cooling for recycling,
Operation of super critical fluid extraction system is controlled from a personal computer.
Personal computer is used to set the operating conditions like pressure, temperature and
Flow rate, PC is programmed to safely shutdown the unit in the case of over pressure or over
Amino acids, phenolic compounds, essential oily, fatty acids, vitamins, hormones, polypeptide, nucleic acids and proteins etc. can be successfully isolated by counter current distribution.
It is also useful in the pharmaceutical industry for purification of pharmaceutical preparations.
For the commercial development the technique of counter current distributed is modified by using the same principle in droplet counter current chromatography.
In this process the fractionation is done by passing the droplets of mobile phase through an immiscible, liquid stationary phase held in small capillary columns.
The process is in limited use due to the complexities of the instruments.
FACTORS AFFECTING MODERN METHOD OF EXTRACTION PROCESS
Nature of drug