Extraction and Separation Techniques PDF

Al-Turath University College Department of Pharmacy Pharmacognosy Lab Stage 2, Second semester Extraction and separation techniques Extraction involves the separation of the medicinally active constituent of plants or animal tissues from the inactive or inert component by using solvent(s) and by usi...

Al-Turath University College Department of Pharmacy Pharmacognosy Lab Stage 2, Second semester Extraction and separation techniques Extraction involves the separation of the medicinally active constituent of plants or animal tissues from the inactive or inert component by using solvent(s) and by using one of the standard extraction procedures. The products that obtained from plants are relatively impure liquids, semisolid or powders, intended only for oral or external use. These total extractive products are called Galenical, which came from the name Galen, the 2nd century Greek physician. Methods of extraction can be divided into: A/ Cold methods 1. Maceration 2. Percolation B/ Hot methods 1. Infusion 2. Decoction 3. Digestion 4. Continuous hot extraction methods a. Ordinary reflux condenser b. Soxhlet apparatus 5. Distillation Cold methods 1- Maceration Principle: extraction of active Cpds with cold solvent by soaking the plant material with the solvent. Procedure: - Carried out at room temperature (15-25) - Place the plant material in a container - Add the solvent - Cover the container - Leave for 2-4 days with occasional agitation and starring - Pour off the solvent in a container - Keep the residual (marc ) material - Filter the solvent - Repeat the extraction using the residual material several times - Mix the obtained solvents together Due to the difficulty to get the active constituent in one maceration process, the procedure may be repeated many times and the solvent obtained then mixed together. Solvent: - Depend on the active constituent (alkaloids, glycosides,… etc) -Alcohol : water in different proportions -Water used because if the alkaloids present in a salt form -Chloroform (non-polar ) used for the extraction of volatile oil and terpenes Cold methods 2- Percolation Principle: extraction of active Cpds with cold solvent by using percolator (which has a porous diaphragm at the bottom) Procedure: - Carried out at room temperature (15-25) - Place the powdered plant material in the percolator and stop the cork - Add the solvent (menstruum) from the upper end. For better extraction, the plant - Allow to macerate for 24hr. material can be soaked with the - Open the cork and allow the liquid to pass solvent ~ 0.5hg before starting the - The extract (percolate) pass through the porous diaphragm procedure - Keep the residual (marc ) material Solvent: - Depend on the active constituent (alkaloids, glycosides,… etc.) - See maceration method Hot methods 1- Infusion Principle: extraction of active Cpds with boiled water by using infusion pot. Procedure: - Place the powdered plant material in the infusion pot - Add the solvent (boiled water) - Cover with heavy lid which contain sieves - Left for a while - Meanwhile, the volatile oil evaporated with steam and deposited on the lid and condenses on the lid - Take the solvent which contain the active Cpds Solvent: - Boiling water Hot methods 2- Decoction Principle: extraction of active Cpds with a continuously heated solvent. This method is used - Hard plant parts like barks, stems and roots which contain a lot of fibers - The extracted Cpd must be heat stable Procedure: - Place the powdered plant material in a container - Add the solvent - Place the container on the source of heat or direct flame - Agitating until the active constituent will be dissolve in the solvent Solvent: - Depend on the active constituent (alkaloids, glycosides,… etc.) - Water, chloroform or ether Hot methods 3- Digestion Principle: extraction of active Cpds with a gentle heated solvent. Procedure: - Place the powdered plant material in a container - Add the hot solvent - Agitating until the active constituent will be dissolve in the solvent Solvent: - Depend on the active constituent (alkaloids, glycosides,… etc.) This method is used were moderate temperature is required Gentle heating allow the solvent to increase its extraction powder Hot methods 4- Continuous hot extraction methods A- Ordinary reflux condenser Principle: extraction of active Cpds with boiled solvent using reflux condenser The reflex method require : - Round bottom flask - Glass made condenser - Heating source - Water source Procedure: - Place the powdered plant material in the flask - Add the solvent - Attach the flask to the condenser - Start heating the flask and open the water source - When the solvent reach its boiling point it will evaporate to the condenser were it condenses and return back to the flask Solvent: - Depend on the active constituent (alkaloids, glycosides,… etc.) This method solvent and the round bottom flask is surrounded by a source of heat Hot methods 4- Continuous hot extraction methods B- Soxhlet apparatus Principle: continuous extraction of active Cpds with boiled solvent The Soxhlet method require : - Round bottom flask - Extracting chamber - Glass made condenser - Porous thimble - Heating source - Water source Procedure: - Place the powdered plant material in the thimble - Place the solvent in the flask - Attach the extracting chamber to the condenser - Start heating the flask and open the water source - When the solvent reach its boiling point it will evaporate to the condenser were it condenses and dropped down to the porous thimble. - The solvent will extract some of the active Cps and then pass through the porous thimble into the flask through a siphon tube and mix with the solvent Solvent: - Depend on the active constituent (alkaloids, glycosides,… etc.) A comparison between ordinary reflux and Soxhlet Reflux Soxhlet Consisting from round bottom flask directly connected to a condenser. Consisting from round bottom flask connected with extracting chamber containing thimble and the extracting chamber connected to a condenser. The plant material is placed together with the solvent in the round bottom flask. The plant material is placed in the thimble separated from the solvent. The extract requires filtration The extract not requires filtration The plant material is directly exposed to the heat The plant material is not directly exposed to heat Hot methods 5- Distillation Principle: extraction of active Cpds with heated solvent using Clevenger The Clevenger method require : - Round bottom flask with 1 or 2 orifices This method is used for extraction of - Glass made condenser volatile oils (orange oil from orange - Heating source peels and clove oil from clove) - Water source Procedure: - As in the reflux method except that the condensed extract is collected in a container Solvent: - Depend on the active constituent