Extraction: It is a process of plant (or) animal tissues with solvent, whereby the medicinally active constituents are dissolved, and most of the inert matter remains undissolved.
The solvent used for extraction is known as “menstruum”. and the inert insoluble material, that remains after extraction is called “marc”
Various extraction processes are :
Classification of extraction
- Solid-liquid extraction: (Leaching) separates soluble constituents from the solid with menstruum.
- Liquid-liquid extraction: It is a method used separate two immiscible liquids, here extraction of a substance from one liquid phase to another liquid phase. It is a basic technique, which is performed using a separating funnel.
Briefly about the process of extraction methods
Methods of extraction
It consists of pouring water over the drugs, then being allowed to keep for 15 minutes, with occasional stirring and filtering of the liquid. The marc is not pressed. Commonly boiling water is used as a menstruum, since it has a greater solvent than cold water.
In this process, the drug is boiled with water for a stated period usually 10 minutes. After boiling the liquid is strained and water is passed through the content of the strainer to make the required volume.
In this process, the drug is extracted by heating at a particular pressure. This will increase the penetration power of the menstruum so that there is complete extraction of the drug. Precaution should be taken so that the increased temperature may not harm the active constituents of the drug.
The various types of maceration processes are:-
A process: for tinctures made from organized drugs e.g. roots, stems, leaves, etc. This process is called “Simple Maceration”.
A process for tinctures made from unorganized drugs such as oleo resins and gum resins. This process is known as “Maceration with Adjustment”.
Process for concentrated preparations which include both “Double Maceration” and ‘Triple Maceration”.
Maceration Process for Tinctures made from Organised Drugs (Simple Maceration).
Apparatus:- A wide-mouth bottle or any other container which can be well-stoppered is used for the maceration process. A closed container is essential to prevent the evaporation of menstruum which is mostly concentrated alcohol. Otherwise, this may lead to variation in strength as no adjustment in volume is made.
Method:- In this process, the drug is placed with the whole of the menstruum in a closed vessel for seven days. During this period shaking is done occasionally. After seven days, the liquid is strained and marc is pressed. The expressed liquid is mixed with strained liquid. It is then filtered to make a clear liquid. The final volume is not adjusted.
- Shaking of the drug during maceration is essential in order to replace the saturated layers around the drug with fresh menstruum.
- After straining, the marc is pressed in a filter press, hydraulic press or hand press, etc. The marc can be squeezed out in a fine muslin piece when the quantity of the drug is very small.
- The pressed liquid is mixed with the strained liquid and then filtered. No final adjustment in volume is made since the volume of pressed liquid is likely to vary with the process of pressing the marc. If the final adjustment in volume is made, it will give variation in the concentration of active principles although the volume of the final preparation may be the same.
- Filtration is necessary to remove insoluble cell contents obtained during the pressing of the marc.
Examples: The tinctures made by simple maceration process are:-
- Tincture of Orange.
- Tincture of Lemon.
- Tincture of Squill.
Extraction may be defined as the treatment of the plant or animal tissue with solvent, whereby the medicinally active constituents are dissolved and most of the insert matter remains undissolved.
i) The solvent used for the extraction is known as “menstruum.”
ii) The inert insoluble material that remains after extraction is called “Marc.”
Apparatus: Three types of percolators are used.
i) Conical percolator: The percolator is made of glass or metal usually copper which is tinned inside. It is conical in shape having a lower diameter of not less than half of the upper diameter.
ii) Cylindrical percolator: The percolator is cylindrical in shape. The upper and lower diameters are the same.
iii) Steam jack percolator: When percolation is carried at a higher temperature, in order to increase the solvent action of the menstrum, the percolator is heated by steam.
Method: Simple percolation process is used for the preparation of tinctures.
There are 3 stages in the official method for preparations of tinctures by simple percolation process. These are:
- Imbibition: The powdered drug is moistened with a sufficient quantity of menstrum and
- Allowed to stand for 4 hours in a closed vessel.
- Pack the moistened drugs into a percolator and add a sufficient quantity of menstrum to saturate the material.
- When the liquid starts coming out from the outlet of the percolator, the outlet is closed.
- Then a sufficient quantity of menstrum is added in order to leave a layer above the drug.
- The moistened drug is left in contact with menstruum for 24 hours.
- During this period, the menstruum dissolves the active constituents of the drug and becomes almost saturated with it.
- Percolation: It consists of the downward displacement of the saturated solution formed in maceration and extraction of the remaining active constituents present in the drug.
- By the slow passage of the menstrum through the column of the drug.
- After collecting 3/4th of the required volume of the finished product or when the drug is completely exhausted, the Marc is pressed.
- Mix the expressed liquid with the percolate.
- Add a sufficient quantity of menstruum to produce the required volume and then filter.
Ex: Preparations made by simple percolation process are; tincture of belladonna, compound tincture of cardamom, and strong tincture of ginger.
Also read: Process of freeze drying