In the extraction process the animal / plant drug is treated with particular solvent. The solvent dissolves the medicinally active constituents in itself but animal or plant tissue and other component are not dissolved in the solvent.
Extraction is the process in which the separation of the soluble constituents occurs from insoluble substance either solid or liquid by processing with a specific solvent.
The active constituents from the crude drug can be separated by different separation and extraction methods. In the extraction process there is a mass transfer process in which transfer of mass occur from soluble material like solid to a fluid. The different factor which effect the process of mass transfer are temperature, agitation, size reduction and others. The extraction may be solid extraction, solid-liquid extraction or liquid-liquid extraction. In the solid separation of the drug the active constituents of a solid drug are extracted from solid substances. In the solid liquid extraction the solid drug is extracted from a liquid solvent. In the case of liquid – liquid extraction liquid solvent is selected to extract the active
constituents present in another liquid. Both liquid are immiscible. Some important term uses in extraction process are Menstrum: Solvent or mixture of solvent use for extraction.
Miscella: Solution with extracted substance.
Rinsing: Dissolution of extractive substance out of disintegrated cell. Lixative or leaching: Water is use as solvent for extraction. Marc: Residue left after extracting the desired constituents.
The various methods of extraction are:
5. Counter current extraction
6. Super critical fluid extraction
7. Hot continuous extraction (soxhalation)
9. Ultra sound extraction
10. Steam distillation
11. Microwave assisted extraction
In the process of maceration the crude drug is immersed into the bulk of menstrum or solvent for at least 3 days (generally 3-7 days). During this period the menstrum is agitated frequently. The menstrum and container should be kept in the stoppered container. The mixture is then filtered or strained through net or sieves. Filter almost all the liquids and then press the marc and clarified liquid by decantation after standing or by filtration. The loss of solvent can be adjusted by prescribed extracted juices. Stoppered container are generally use for maceration so that the loss of solvent by evaporation should be avoided. The drug is allow to stand for 3-7 days with menstrum so that solvent penetrate the cell more perfectly And get the time for portioning of active constituents into the solvents. Frequent agitation help the distribution of active constituents in the entire solvent and prevent localization of active constituents around the tissue and cell.
The maceration may be of various types like:
4. Kinetic maceration
The maceration process is use for the concentrated preparation where the entire menstrum is segregated into two parts (for double maceration) or in three parts (in triple maceration). Each menstrum are use individually for the maceration process. In this process the drug menstrum ratio is low and extraction is performed with less amount of menstrum.
Like the simple maceration kinetic maceration is also preceded into the room temperature but the single difference is that the material is under constant motion. The intensity and type of movement play important role in the maceration.
In the re-maceration process part of the solvent is added to the drug. After filtration process the residue is treated with the remainder solvent.
Uses of Maceration:
BP permits the preparation of the tincture by maceration methods of following drugs Squill tincture, Catechu tinctures, Senna liquid extract compound Benzoin tincture and opium tincture. Mother tinctures of homeopathic Pharmacopoeia are prepared by maceration methods.
Maceration is most widely use methods of extraction. Maceration can be performed easily with pharmacist lab with small amount of sample. There are number of drug which can extract by only maceration methods due to their high swelling property or high mucilage content.
MICROWAVE ASSISTED EXTRACTION
The electromagnetic radiation which have a frequency 0.3-300 GHz are called microwave. Industrial microwaves are generally operated as 2.45 GHz so that it avoid the interferences of domestic instruments like radio and other. Due to their electromagnetic property microwaves contain magnetic and electric field. They are perpendicular to one another. Electric field generates heat through two simultaneously method i.e. ionic conduction and dipolar rotation. Microwave transfer the energy to solid matrix and solvent homogenously and very efficiently. Substance (solid matrix and solvent) absorb the energy as per dielectric constant. The plant material which is present in the microwave transport solvent absorbs the heat of microwave which causes the heating of moisture present inside the drug. Evaporation occurs due to heating of moisture and this will produce high vapour pressure. This high vapour pressure crack the cell wall of plant drug and release the active constituent into the solvent.
The extraction property of the solvent and their interaction with microwave can be altered by using solvent mixtures.
The benefit of microwave assisted extraction are that less solvent are required, time consumption is less, high extraction rate and good reproducibility but additional centrifugation or filtration are necessary to remove residue and the efficiency will be poor if the solvent or compound have non polar property or they are volatile. Example- Extract of glycyrrhizic acid from mulethi.
SUPER CRITICAL FLUID EXTRACTION
A critical point is a particular temperature and pressure at which two phases (like liquid and vapour) can co-exist. The substance at above the critical temperature and pressure or above the critical point is known as supercritical fluid. The property of super critical fluid is in between gas and pure liquid so that they are also known as dense gases or compressible Liquid. Super critical fluid has good solvation power, low viscosity, higher diffusibility and good penetrating power. By the help of super critical fluid extraction technique we can separate the constituents from the drug with the help of super critical fluid. Generally we can separate the constituents from the solid matrix but it may also be liquid. CO2 is one of the most common super critical fluid. To make CO2 super critical fluid the critical temperature is 31°C and critical pressure is 74 bars.