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Extractionofalkaloids

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SajeenaCH
SajeenaCH

This document describes the Stas-Otto method for extracting alkaloids from powdered plant materials. The method involves three stages: (1) treating the powder with an alkali to free alkaloids, (2) extracting the freed alkaloids using an organic solvent, (3) converting the alkaloids to sulfates and extracting them into an aqueous layer, then making the layer alkaline to precipitate the purified alkaloids. Variations include using water-soluble organic solvents for initial extraction. Purification techniques for the crude alkaloidal mixture include crystallization, steam distillation, chromatography, and gradient pH extraction based on differences in alkaloid basicity.

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EXTRACTION OF ALKALOIDS
STAS-OTTO METHOD ?The technique involve the distribution of alkaloidal bases between acid or aqueous solution and immiscible organicsolvent. MethodI:
A) stage1:--Powdered material is moistened with water and mixed with alkali like sodium &potassium carbonate ,ammonia, lime. Concept :--Lime(calciumhydroxide),combines with acid , tannins, and other phenolic substances andsets free alkaloids. B).Stage2:-- extract the free alkaloids by hot continous percolation with chloroform or any other organic solvents.
?Concept :-the free alkaloids dissolve together withother substances soluble insolvent. ? Stage3:--agitate the chloroform soln. With successive portion of dil.Sulphuric acid separating the aqueouslayer before adding the next portion ofacid. ?Concept :-the alkaloids are converted into alkaloidal sulphates, which being soluble in water,pass intoaqeous layer.
? Stage4:--Make the mixed aqueous liquidalkaline with ammonia, collect the precipitate that forms, wash with water anddry. ?Concept :-Ammonia decomposes the alkaloidal sulphates forming ammonium sulphates ,solublein water ,and the free alkaloid which being practically insoluble in water isprecipitated.
LOGO Powdereddrug Containingalkaloidalsalts ? Exhaust with org. Solvent like CHcl3, ether ? Total extracts ? Conc. & Shake with acid like dil. H2so4 Freealkaloids Residual organicfraction (Pigments, fats & weak bases or chloroform soluble alkaloidssulphates) organic soln (alkaloidalbases) Moisten & render alkaline with Na2CO3, lime, NH3 Defatted if necessary Aq.Acidsoln (Alkaloidal salts) Make alkaline extract with immisicible solvent Residual aq. Fraction Remove solvent crudealkaloidalmixture
Method I I: The powder is extracted with water soluble organic solvents such as MeOH or EtOH which are good solvents for both salts and free bases. ? And the resultant extract is submitted to same process as that of method I.
PURIFICATION OF ALKALOIDS :: 1.DIRECT CRYSTALLISATION FROM SOLVENT. 2. STEAM DISTILLATION. 3. CHROMATOGRAPHY TECHNIQUES. 4. GRADIENT pH TECHNIQUES.
GRADIENT pH TECHNIQUES : ? Though alkaloids are basic in nature, there are variations in the extent in the basicity of various alkaloids of the same plant. ? Depending on this character pH of the aqueous solution is increased gradually by 0.5 increment upto pH 9 , and extraction is carried out at each pH level with organic solvent, ? by this way alkaloids with different basicity are extracted.

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Extractionofalkaloids

  • 2. STAS-OTTO METHOD ?The technique involve the distribution of alkaloidal bases between acid or aqueous solution and immiscible organicsolvent. MethodI:
  • 3. A) stage1:--Powdered material is moistened with water and mixed with alkali like sodium &potassium carbonate ,ammonia, lime. Concept :--Lime(calciumhydroxide),combines with acid , tannins, and other phenolic substances andsets free alkaloids. B).Stage2:-- extract the free alkaloids by hot continous percolation with chloroform or any other organic solvents.
  • 4. ?Concept :-the free alkaloids dissolve together withother substances soluble insolvent. ? Stage3:--agitate the chloroform soln. With successive portion of dil.Sulphuric acid separating the aqueouslayer before adding the next portion ofacid. ?Concept :-the alkaloids are converted into alkaloidal sulphates, which being soluble in water,pass intoaqeous layer.
  • 5. ? Stage4:--Make the mixed aqueous liquidalkaline with ammonia, collect the precipitate that forms, wash with water anddry. ?Concept :-Ammonia decomposes the alkaloidal sulphates forming ammonium sulphates ,solublein water ,and the free alkaloid which being practically insoluble in water isprecipitated.
  • 6. LOGO Powdereddrug Containingalkaloidalsalts ? Exhaust with org. Solvent like CHcl3, ether ? Total extracts ? Conc. & Shake with acid like dil. H2so4 Freealkaloids Residual organicfraction (Pigments, fats & weak bases or chloroform soluble alkaloidssulphates) organic soln (alkaloidalbases) Moisten & render alkaline with Na2CO3, lime, NH3 Defatted if necessary Aq.Acidsoln (Alkaloidal salts) Make alkaline extract with immisicible solvent Residual aq. Fraction Remove solvent crudealkaloidalmixture
  • 7. Method I I: The powder is extracted with water soluble organic solvents such as MeOH or EtOH which are good solvents for both salts and free bases. ? And the resultant extract is submitted to same process as that of method I.
  • 8. PURIFICATION OF ALKALOIDS :: 1.DIRECT CRYSTALLISATION FROM SOLVENT. 2. STEAM DISTILLATION. 3. CHROMATOGRAPHY TECHNIQUES. 4. GRADIENT pH TECHNIQUES.
  • 9. GRADIENT pH TECHNIQUES : ? Though alkaloids are basic in nature, there are variations in the extent in the basicity of various alkaloids of the same plant. ? Depending on this character pH of the aqueous solution is increased gradually by 0.5 increment upto pH 9 , and extraction is carried out at each pH level with organic solvent, ? by this way alkaloids with different basicity are extracted.