Extraction: Definition, Objectives / Applications Principles, Working  Classification, Method and Application.

Extraction: Definition, objectives/application principle, working , classification, method and application.

Definition: Extraction is withdrawal or removal or isolation of chemical constituents from crude drugs. Solvent used to extract or remove or isolate chemical constituents from crude drug is called menstruum. Residue obtained after complete extraction of active constituents from crude drug is called marc.

Objectives: To withdraw active constituents from crude drugs for pharmaceutical or therapeutic uses.

Classification: Extraction process can be classified into following four groups

• 1. Infusion

• 2. Decoction,

• 3. Digestion,

• 4. Maceration

  • i. Maceration process for organised drugs,

  • ii. Maceration process for unorganised drugs,

• 5. Percolation

  • i. Simple percolation

  • ii. Percolation process for concentration preparation

    • a. Reserve percolation,

    • b. Modified percolation,

  • iii. Continuous hot percolation.

MACERATION

Process to extract chemical constituent from crude drug by soaking menstruum into crude drug to extract its chemical constituents is called maceration.

Principle of maceration: Chemical constituents from crude drug come out with menstruum by diffusion process. Menstruum enter crude drug. Chemical constituent’s dissolution in menstruum takes place inside crude drug. Solution comes out from crude drug by diffusion and at the same time fresh menstruum enters into crude drug. Thus cycle continue till concentration of active constituents inside crude drug become equal to concentration of drug in menstruum outside crude drug.

a. Simple maceration for organised drugs (Maceration without final volume adjustment): Crude drug with specific cellular structure is called organised drug. Ex leaf, bark, flower, fruit, etc.

Method (Procedure): Mix coarsely powdered crude drug with menstruum in wide mouth container with lid. Ratio of crude drug and menstruum shall be 1:10. Set as side for seven days with occasional stirring. Strain the liquid after seven days. It is macerate. Press the marc. It is expressed liquid. Mix macerate and expressed liquid. Filter it to get clear extract. This extract is also called macerate. Final volume is not adjusted.

Explanation

• 1. Coarse or moderately coarse crude drug is used. It increases the surface area of crude drug that increases rate of extraction. Fine powder of crude drug is not used. It will be difficult get clear extract (macerate) after filtration.

• 2. Wide mouth container with lid is used. It will be easy to pour menstruum, place crude drug into container. Stirring of mixture shall also easy. Lid is used to cover container mouth. It will stop evaporation of menstruum during seven days of maceration process.

• 3. Maceration is carried out for seven days. Menstruum takes time to penetrate into organised crude drug and extract chemical constituents from organised crude drug. Seven days allow complete extraction of chemical constituents from organised crude drug.

• 4. Stirring is done occasionally to displace saturated layer of menstruum around crude drug.

• 5. Marc is pressed to avoid wastage of menstruum and chemical constituents of crude drug.

• 6. Filtration is carried out to remove insoluble components of crude drug in macerate.

• 7. Final volume is not adjusted to avoid dilution of macerate.

Examples are tincture of lemon, tincture of orange.

b. Simple maceration process for unorganised crude drugs (Maceration with final volume adjustment): Crude drugs without simple cellular structure is called unorganised drug. examples are gum, resins, etc.

Method (Procedure): Mix unorganised drug with 80% of total menstruum to be used in wide mouth container with lid. Set as side for 2 to 7 hours with occasional stirring. Decant the solution. Do not press the marc. Adjust the volume by passing rest 20% of menstruun through marc.

Explanation

• 1. Maceration period is 2 to 7 hours: Unorganised crude drug behaves like simple chemical. Menstruum easily penetrates into unorganised crude drug. Thus 2 to 7 hours is sufficient for maceration.

• 2. 80% menstruum is used: 80% menstruum is more than sufficient to dissolve and extract chemical constituents from unorganised crude drug.

• 3. 20% remaining menstruum: It is used as washing menstruum. It is used to wash marc to extract remaining chemical constituents in marc.

• 4. Marc not pressed: Marc does not contain any chemical constituent thus it is not pressed. It is also not practical to press marc obtained from unorganised crude drug like gum or resin.

c. Multiple macerations: It is carried out to make concentrated preparation. Simple maceration process is carried out multiple times on a crude drug. There are two types of multiple macerations. These are double maceration and triple maceration.

• 1. Double maceration: Menstruum is divided into two equal parts. Maceration is carried out using same crude drug. It is carried out to make concentrated extract from organised drug that can be pressed after extraction. Volume of first maceration is calculated by using following formula:

• Volume of menstruum for first maceration:

• Volume of menstruum retained by the crude drug: It is calculated by using known weight of crude drug and known volume of menstruum. Mix both, allow macerating for 48 hours, strain and pressing marc. Mix strained liquid and expressed liquid. Measure the volume. Difference between total volume of menstruum used and total macerate obtained is volume of menstruum retained by the taken amount of crude drug.

• First maceration: Mix calculated volume of menstruum with whole coarse crude drug. Macerate it for 48 hours. Strain it and press the marc. Mix strained macerate and expressed liquid.

• Second maceration: Mix rest of menstruum with marc obtained from first maceration. Macerate it for 24 hours. Strain it and press the marc. Mix both liquid.

• Mix the liquid obtained from the first maceration and second maceration. Set aside for 14 days and filter it or concentrate the macerate by heating upto required strength and filter it. Examples are concentrate infusion of orange, concentrate infusion gentian, etc

2. Triple macerations: Menstruum is divided into three parts for maceration of fix amount of crude drug. It is carried out to make concentrated extract from unorganised drug that cannot be pressed after extraction process. Maceration is carried out three times. Following formulae are used to calculate volume of menstruum to be used in first maceration, second maceration and third maceration:

First maceration: Mix calculated volume of menstruum with whole coarse crude drug. Set aside for 1 hour with occasional stirring. Strain it.

Second maceration: Mix calculated amount of menstruum with marc obtained from first maceration. Set aside for one hour with occasional stirring. Strain the macerate.

Third maceration: Mix rest amount of menstruum with marc obtained from second maceration. Set aside for one hour with occasional stirring. Stain the macerate.

First macerate is a concentrated preparation. Set aside it. Mix second macerate and third macerate. Both are dilute macerates. Evaporate the mixture of second macerate and third macerate up to specified volume. Mix it with the first macerate. Add alcohol 90% v/v equal to 20% of total volume of final product. Alcohol 90% v/v acts as preservative. Add sufficient water to make up to required volume.

PERCOLATION

Percolation is movement of fluid through porous material. Fluid moves downward through porous material by displacing other fluid. Thus percolation is also called “downward displacement method”. Percolation is a process to extract chemical constituents from crude drug by passing menstruum through porous bed of crude drug. Extract obtained by percolation is called percolate.

1. Simple percolation: In simple percolation ratio of drug and percolate is 1:4. Percolator is used as apparatus for simple percolation. Percolator is made of glass or metal especially either copper or stainless steel. There are two types of percolator.

• Conical percolator: It is conical in shape. It has open bottom fitted with tap and open top fitted with lid. There will be little chance to choke flow of menstruum during percolation process. But there will be loss of menstruum by evaporation due to wide opening (diameter) of upper most part of conical percolator. It is not suitable for volatile menstruum such as spirit.

• Cylindrical percolator: It is cylindrical in shape. It has open bottom fitted with tap and open top fitted with lid. It is suitable for volatile menstruum due to its low diameter than cylindrical percolator. But flow of menstruum may be choked due to swelling of crude drug inside percolator. Thus it is suitable for crude drug with less chance swelling of crude drug.

Method (Process): There are four steps in simple percolation process. These are Imbibition, percolator packing, maceration and percolation.

• i. Imbibition: Moisten the Coarse or moderately coarse crude drug with the menstruum. Set aside for 4 hours in a closed wide mouth container.

• Explanation: Coarse or moderately coarse crude drug is used to increase the surface for extraction and there will be uniform packing of crude drug in percolator. Crude drug is moistened

• · To make crude drug soft and allow swelling before its packaging in percolator. If swelling occurs inside percolator it will make tight packing and will block flow of menstruum.

• · To remove air present in between crude drug particles.

• · To block wash out of crude drug fine particles by sticking it with coarse crude drug

• ii. Packing of percolator:

  • · Pass the moistened crude drug through sieve to break lumps. Percolator has open bottom fitted with tap.

  • · Place moist glass wool at bottom of percolator. It will prevent blockage of tap opening by the crude drug.

  • · Add 10% of total moist crude drug into percolator and level it. Again add 10% of total moist crude drug and level it. In this way add all moist crude drugs into percolator. It will form uniform packing of moist crude drug inside percolator. Uniform packing is required for uniform distribution of menstruum through out packing in percolator. Packed crude drug should not occupy more than 70% of percolator volume.

• Packing should not be too tight that stop flow of menstruum. It should not be too loose that allow free flow of menstruum. In both case there will be no or little extraction.

  • · Place a piece of moist filter paper over packing of crude drug inside percolator. Place wash sand over this filter paper. Filter paper stop mixing of washed sand with crude drugs during movement of menstruum through crude drug packing. Sand will protect uniform packing of crude drug while adding menstruum into percolator.

  • · Open tap of percolator. Add menstruum slowly into percolator. Allow to move it downward through packing. Close the tap when menstruum starts to come out from tap. Continue addition of menstruum to maintain a level of menstruum over sand inside percolator. Layer of menstruum over sand will stop drying and cracking of crude drug packing upper layer during process.

• iii. Maceration: Close the percolator by using its lid. Set aside for 24 hours for maceration. Menstruum will penetrate into crude drug to dissolve chemical constituents. Low quantity of menstruum shall be required for percolation due to this step. This step extracts most of the chemical constituents from crude drug. Lid is used to close the percolator to prevent loss of menstruum due to evaporation.

• iv. Percolation: Open the tap to collect extract drop wise after completion of maceration step. Collect 80% volume of total required percolate. During this process add sufficient menstruum to maintain layer of memnstruum over percolator packing. Then slow down rate of percolation. Collect percolate till crude drug get exhausted. Normally rate collection varies from 10 to 30 drops per minute.

• Test to check drug exhaustion: Evaporate few ml of percolate. No residue after complete evaporation indicates drug exhaustion. Measurement of specific gravity of percolate also helps. If specific gravity of percolate equal to specific gravity of menstruum indicates drug exhaustion. Specific test related to chemical constituents to be extracted also gives result regarding complete exhaustion.

2. Percolation for concentrated preparation: There are two types of percolation process to prepare concentrated preparation. These are reserve percolation and modified percolation.

• Reserve percolation: First part of percolate obtained in simple percolation i.e. 80% of total percolate is kept reserved. Second part of percolate from simple percolation process collected separately. Second part of percolate is either evaporated or distilled to form a soft mass of percolate. This soft mass of percolate is dissolved in the first part of reserve percolate. Sufficient menstruum is added toi make required volume.

• Modified percolation process: In simple percolation drug and percolate ratio is kept 1:4. This ratio is reduced to 1:3 in modified percolation process.

• 1. Continuous hot percolation:

• It is also called soxhlet extraction or soxhelation. Small volume of hot menstruum passes through crude drug repeatedly and continuously to extract chemical constituents from crude drug in continuous hot percolation.

• Apparatus: It consists of round bottom flask, Soxhlet extractor (extraction chamber), and condenser. Soxhlet extractor has a side tube. It carries menstruum vapour from round bottom flask to condenser. Soxhlet extractor has also another side tube that acts as siphon. It carries menstruum from soxhlet extractor to round bottom flask by siphon mechanism.

• Appararus arrangement: Make a thimble of filter paper. Thimble prevents chocking of side tube that acts as siphon. Place thimble into soxhlet extractor. Pack moist powdered crude drug into thimble to form uniform packing.

• Place menstruum into round bottom flask. Place round bottom flask on heat source. Attach lower part of soxhlet extractor with round bottom flask. Attach upper part of soxhlet with a condenser.

• Procedure: Boil menstruum inside round bottom flask. Vapour will enter into soxhlet through one side tube then into condenser. Condensed liquid from condenser shall fall on to packed drug column in the thimble inside soxhlet. Level of menstruum inside soxhlet will rise up to top. At this level menstruum will be siphoned off from soxhlet into round bottom flask through siphon tube. soxhlet will become empty. Continuous heating of round bottom flask generate menstruum vapour continuously. It will enter into soxhlet then to condenser and condensed menstruum fall on crude drug column.

• Continue the process to fill and empty soxhlet 15 times to extract the active constituents from crude drug.

• Advantages

  • 1. It is suitable to extract chemical constituents from very hard crude drug,

  • 2. It is suitable to extract chemical constituents with low solubility,

• Limitations:

  • 1. It is not suitable for thermo labile chemical constituents of crude drug.

  • 2. It requires pure menstruum that has fixed boiling point

  • 3. It is not suitable fro crude drug that blocks soxhlet. Such as gum, resin, etc

INFUSION

• Mix menstruum (solvent) with crude drug in a container. Set aside for 15 minutes with occasional stirring. Filter the mixture. Marc is not pressed. Final volume is not adjusted. Pressing of marc may express colloidal extract. Volume makes up dilute the preparation. Filtrate contains chemical constituents of drug. Filtrate is called infusion. Hot menstruum is preferred over cold menstruum. Normally water is used as menstruum.

• It should be consumed within 24 hours. Filtrate obtained by this process is called infusion. Extract obtained by percolation and maceration process is also called infusion. But infusion obtained from maceration or percolation process is a concentrated preparation. They contain alcohol as preservative thus they can be stored for longer duration.

DECOCTION: Crude drug is boiled with menstruum normally water for 10 minutes. After filtration water is passed through marc to make the volume. Filtrate is called decoction.

DIGESTION: Chemical constituents are extracted by using hot menstruum under pressure. High pressure increases the efficiency of hot menstruum penetration.

Alok Bains