Pharmaceutical Extraction Techniques Quiz

Extraction and Isolation of Active Constituents

• The process of separating the active portions of plant or animal tissues from inert components using selective solvents in standard procedures is called extraction.
• Topics covered in the lecture include definition of extraction, steps involved in extraction, extraction methods, evaporation of plant extracts, and separation/isolation of active plant constituents.
• Steps involved in extracting medicinal plants generally include sample preparation, size reduction, extraction, filtration, concentration, and drying.

Preparation of Plant Samples

• Carefully select plant material to avoid adulterated or infected samples.
• Authenticate the selected sample with a taxonomic expert.
• Immediately immerse fresh material in boiling alcohol to stop enzymatic activity.
• Dry plant material, if required, under controlled conditions before extraction.

Instruments Used in Extraction and Preparation of Medicinal Plants

• Disc mill
• Soxhlet extractor
• Vacuum column
• Freeze dryer
• Rotary evaporator

Steps Involved in Size Reduction

• Hammer or disc mill
• Cryogenic milling (new grinding method): suitable for thermolabile compounds (volatile oils), provides a large surface area with minimal loss of compounds during cooling (-80°C) using dry ice and liquid nitrogen.

Selection of Solvent for Extraction

• The solvent selectively dissolves the active material and removes inactive/inert material to leave a higher concentration of active components in the plant sample.
• Polar solvents dissolve polar compounds (sugars, alkaloids) and non-polar solvents dissolve non-polar compounds (fats, waxes).
• Solvent mixtures may increase the solubility of compounds.

Extraction Processes

• Processes like infusion, decoction, and digestion are rarely used for extracting drugs; maceration and percolation are more important in most pharmacopeias for extracting crude drugs.

Maceration

• Maceration involves immersing the crude drug in a bulk solvent (menstruum).
• Repeated maceration can be more efficient than single maceration, especially when active constituents are valuable, as some active principle may be lost in the initial pressing.

Infusions

• Dilute solutions containing readily soluble constituents of crude drugs.
• Fresh infusions were formerly prepared by macerating the drug in cold or boiling water for a short period.
• Infusions are susceptible to fungal and bacterial growth and should be dispensed within 12 hours of preparation.

Infusion Preparation Methods

• Coarsely powder the drug (avoiding very fine powder).
• Moisten 50 grams of the drug with 50 ml cold water.
• Allow to stand for 15 minutes.
• Add 900 ml of boiling water, cover tightly, and let stand for 30 minutes.
• Strain the mixture and add enough water to measure 1000 ml.

Decoction

• Used for water-soluble and heat-stable constituents of hard and woody crude drugs.
• Small pieces of the drug are boiled in the menstruum (water) for 10-15 minutes.
• After boiling, the liquid is cooled, filtered, and additional water added to achieve the desired volume.
• Decoction is no longer an official method in most pharmacopeias.

Digestion

• A modified form of maceration where gentle heat is applied to increase the action of the menstruum.
• Applicable to drugs where moderately elevated temperatures are not detrimental.

Percolation

• A continuous flow of solvent through a bed of crude drug material.
• Plant sample is placed in a percolator.
• Sufficient menstruum is added to maintain a layer above the drug (the drug should be fully submerged at no time) and stand for 24 hours.
• After maceration, the outlet is opened, and the solvent is percolated at a controlled rate with continuous addition of fresh solvent.

Continuous Hot Extraction (Soxhlet Extraction)

• Used for drugs where penetration of the menstruum into the tissue is slow, and the solute is not readily soluble.
• Small volumes of hot menstruum are passed through the drug repeatedly to extract the active constituents until the drug is exhausted.

Soxhlet Extractor

• Apparatus used for continuous hot extraction using a cyclical process to extract components from drugs.

Distillation

• Separating components of a liquid mixture by vaporization and subsequent condensation at a different location.
• Fractional distillation is used to isolate volatile oils.
• Steam distillation is used to isolate volatile oils and hydrocyanic acid from plant materials. Distillation failed to isolate components present in minor quantities, so gas chromatography is usually used.

Other Methods for Volatile Oils Extraction

• Cold Fat Extraction (Enfleurage)
• Expression
• Sponge expression
• Écuelle à piquer
• Machine abrasion

Evaporation of Crude Drug

• Evaporation is a quality parameter for the eluate.
• Temperature and evaporation time are crucial factors when extracting fragile (thermo-labile) compounds.
• Evaporation is carried out using a cautious vacuum evaporation technique (rotary evaporator) at temperatures not exceeding 55°C.

Separation and Isolation of Plant Constituents

• Isolation and purification of plant constituents are the most difficult steps in phytochemical research.
• Fractionation techniques are required to separate compounds belonging to the same chemical family.

Methods for Plant Constituent Separation and Purification

• Sublimation
• Steam distillation
• Fractional liberation
• Fractional crystallization
• Adsorption chromatography (TLC, GSC)
• Chromatography (PC, GLC, HPLC)
• Supercritical fluid chromatography

Sublimation

• A method for isolating components, such as caffeine from tea, by their ability to transition directly from solid to gaseous state (without becoming liquid).

Detailed Chromatography Techniques for Separation and Isolation

• Adsorption chromatography: relies on the selective adsorption of compounds onto a stationary phase (e.g., charcoal). TLC is an example.
• Partition chromatography: separates compounds based on their different partition coefficients between an aqueous and immiscible organic liquid. Paper and HPLC are relevant examples.
• Supercritical fluid chromatography: uses carbon dioxide as a mobile phase, providing faster flow rates than standard HPLC and producing solvent-residue-free extracts at moderate temperatures.

Factors influencing plant extract production

• Physicochemical properties of plant constituents will influence the method used to obtain the constituent.

Test your knowledge on the extraction processes used in the pharmaceutical field. This quiz covers various steps, methods, and instruments essential for obtaining medicinal plant extracts. Assess your understanding of how extraction impacts the effectiveness and quality of pharmaceutical products.