Extraction Methods in Pharmacy

Extraction is the initial step in obtaining the desired natural products from crude materials. Human diseases have been prevented and treated exclusively by organic medicines for thousands of years. The development of drugs relies heavily on natural products. For the extraction and isolation of these bioactive natural products, it is vital to develop efficient and effective extraction methods.

Methods of Pharmaceutical Extraction:

• Maceration

• Infusion

• Digestion

• Decoction

• Percolation

• Soxhlet Hot Continuous Extraction

Let us study the Extraction methods in Pharmaceutical analysis and why the extraction method is important in pharmacy.

• Maceration: This process involves placing the coarsely powdered crude drug with an adequate amount of the solvent in a stoppered container. It is then agitated frequently for at least 3 days at room temperature until its soluble constituents dissolve. A filtration or decantation is performed after a period of standing, and the liquids are clarified by separating the marc (the damp solid material).

• Infusion: Using cold or boiling water, the crude drug is macerated for a short time to produce fresh infusions. Water-soluble drugs are diluted into these solutions.

• Digestion: In this method of extraction, gentle heat is used to macerate the product. Moderately elevated temperatures are suitable for this method. As a result, the menstruum (solvent used for extracting the drug) has a higher solvent efficiency.

• Decoction: This process involves boiling the raw drugs for a fixed amount of time in a certain volume of water. They are then cooled and filtered. A water-soluble, heat-stable constituent can be extracted using this method. Kawath, an Ayurvedic extract, is typically prepared through this process. During the extraction process, the volume of the crude drug is reduced to one-fourth of its original volume by boiling it. The dense extract is then filtered and used directly or processed further.

Percolation

• There is generally a percolator (a narrow, conical vessel with a hole at either end)

• The solid ingredients are moistened with the specified amount of menstruum and are filled into the tightly-closed percolator

• All ingredients are then packed and closed with the percolator’s top

• The mass is then covered with additional menstruum to form a shallow layer and macerated in the closed percolator for 24 hours

• A slow drip of liquid is allowed from the percolator’s outlet after it is opened. The percolate is diluted by the addition of additional menstruum as necessary so that it measures about three-quarters of the finished volume

• Percolate is then prepared by pressing the marc, and then adding the expressed liquid

• The liquid is clarified through filtration or standing and decanting, after adding sufficient amounts of menstruum. This process is commonly used to extract active ingredients

Soxhlet Hot Continuous Extraction

• In this method, coarsely ground raw drugs are filled inside a porous bag called a thimble. This is then put inside the chamber of the Soxhlet apparatus

• The Menstruum is heated in the flask. The vapour evolved is then passed through the condenser where it is condensed. This condensed menstruum is then allowed to drip on the thimble which contains the raw drug. Just by the contact of the extractant, the extraction is caused

• The liquid content in the chamber will syphon into the flask when the level of the syphon tube reaches the top

• Continually, this process is carried out until a drop of solvent from the syphon tube evaporates without leaving any residue

• With this method, a much smaller amount of solvent is needed to extract large quantities of the drug, which gives it an advantage over previously described methods

Factors Affecting Extraction Process

Inert Solutes

• Solutes are capable of exhibiting physical as well as chemical interactions that alter their apparent partition coefficient between different solvents. It is therefore important to take this into account when choosing an extraction system

• Typically, the partition coefficients of two immiscible solvents may not be sensitive to temperature when their concentrations are fairly low and/or the two solvents are more or less immiscible. From the solubility of the substance in the two solvents, it is easier to estimate the effect of temperature on the partition coefficient

• Matkovitch and Cristian determined that three inert solutes (calcium chloride, magnesium chloride, and sucrose) were most useful for salting acetone from water

• When used judiciously and effectively, inert solutes can also be useful in developing efficient extraction procedures from water into solvents such as acetone, methanol and ethanol that, in the absence of salt, completely mix with water. A saturated aqueous solution of CaCl₂ which separated into an acetone layer contained exclusively 0.32 ± 0.01% water (v/v) and 212 part per million salts (w/w) at equilibrium

Associate Ion Pair Formation in Solvent Extraction

• Ion pair formation in solvent extraction is the addition of an oppositely charged ion to a solution to allow extraction, which is used for the extraction of ions into organic phases

• The formation of ion pairs is significant since extraction is often unexpected. An ion-pair formation in solvent extraction is an association of an anion and a cation, which is why it generally occurs in polar or nonpolar solvents

• A typical ion pair consists of a large organic anion and a much smaller cation

• Further, the resulting ion-pairs are very soluble in polar solvents, which facilitates extraction under these experimental conditions where no single component can be extracted

Why is the extraction method important in pharmacy?

Basic extraction procedures are used for crude drugs only to obtain therapeutically useful components and to remove inert components by treating them with a selective solvent known as Menstruum.

Conclusion

In this study material, we learned about Extraction methods in Pharmaceutical analysis. We also learned why the extraction method is important in pharmacy. There are mainly six types of extraction processes. Maceration, Infusion, Digestion, Decoction, Percolation and Soxhlet Hot Continuous Extraction. We gained knowledge about the factors affecting the extraction process. They are inert solutes and the associate ion pair formation.

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