nevry (Stranger)
05-11-02 07:57
No 307402
      natural alkaloid salts  Bookmark   

Most alkaloids are non-polar, so when extracting them from a natural source(plant), they must be in a salt form because they are water soluble. Which salt of the alkaloid does the plant produce?

- nevry.

- nevry.
05-11-02 11:21
No 307464
      Forget something?  Bookmark   

Uh... so to which of the billions of plants on Earth are you referring?

She came from Planet Claire, all the trees are red. Noone ever dies there, noone has a head.
05-11-02 11:50
No 307470
      Ahumm,  Bookmark   

The plant doesn't do it, you must do it by extracting the alkaloids first, and then transform them into salts by means of a diluted acid wash. Depending on which salt you want, you choose your acid, like HCl for chlorides, H2SO4 in alcoholic medium for sulfates, Acetic acid for acetates, etc.
Choice of the strength and kind of acid wash for any specific alkaloids should be found in literature first. LT/

05-12-02 19:21
No 307795
      yes, but...  Bookmark   

many extractions call for nothing but water in the preliminary plant extraction(followed by the a/b). If the alkaloids were in freebase form while in the plant they would not dissolve in the water.

- nevry.

- nevry.
05-13-02 03:34
No 307920
      Solubilities  Bookmark   

If the alkaloids were in freebase form while in the plant they would not dissolve in the water.

Many alkaloids are soluble in water, such as ephedrine laugh

05-13-02 06:50
No 307934
      stochastic salts  Bookmark   

Back to the original question: Plants are not producing defined crystalline salts, instead they produce a soup of myriads of different organic and inorganic ions. On evaporation stochastic salts will form smile.
05-13-02 16:01
No 308148
      ahhhh  Bookmark   

so, to make shure i got your answer strait:

plants DO form salts of the alkaloids, but not a specific salt; just whatever acid is floating around in the plant.

If I got your question right; are all the alkaloids in the plant in salt form; would an extraction with dilute HCl be prefered to just plain H2O(converting the freebase moleicules in the plant to salt form...)?

- nevry.
05-13-02 22:35
No 308242
      No, plants contain ions, salts are formed if you ...  Bookmark   

No, plants contain ions, salts are formed if you dry the plant... laugh

Usually the plants maintain a slightly acidic pH at which the amines are protonated (i.e. in their "salt form"), but to be sure you may add a small amount of extra acid.
05-15-02 14:28
No 308931
(Rated as: Good Explanation)

From the article in Thorpe's Dictionary of Applied Chemistry on alkaloids:
Method of Extraction and Isolation
Generally speaking, alkaloids, whether occurring in the free state or as salts of organic acids, are extracted from the finely powdered material by means оf strong spirit. After distilling off the alcohol, the bases are extracted from the residue by dilute acids, liberated by addition of аmmoniа or sodium carbonate and extracted by chloroform, ether or carbon tetrachloride. This gives the total alkaloidal content of the plant, except where a quaternary base is present, when methods similar to those used with simpler bases, eg precipitation with mercuric chloride or phosphotungstic acid, are utilized. Certain stable alkaloids may be extracted from a mixture  of the finally powdered plant with lime or magnesia by an organic solvent; in other cases (eg caffeine in tea) extractions with boiling water may be employed. The “total alkaloids” obtained by the above methods are mixtures for which no general method of separation can be given. In some cases caustic soda may be used to separate the phenolic from the non-phenolic bases; in others, fractional extraction of the ether or chloroform solution of the bases with acid Ьгings about а separation, or, again, а fractionation may be effected by regenerating the bases from acid solution by an alkali in the ргesenсe of light petroleum or ether, in which only а part of the mixture is soluble. After вuitable preliminary treatment on these lines, alkaloids often crystallise as the free base, but if not, it is generally possible to crystallise а salt with а strong or weak acid.
The choice of the proper acid is sometimes of great importance, e.g. for physostigmine the salicylate is the best salt, and for ergotoxine the phosphate. Acid oxalates are frequently valuable, whilst aurichlorides are useful for Solanaecous alkaloids and picrates for simple bases, but no general rule can be given. In exceptional саses it may be convenient to add an ethereal solution of the acid to that of the alkaloid is dry ether. Excess of acid should be avoided and the precipitated salt can be washed by decantation, filtered, and crystallized. For further information concerning the methods of separating and characterising alkaloids, see Allen's  Commercial Organic Analysis vol vii, 1927, 5-13. For the large-scale manufacture of alkaloids consult J. Schwyzer, Die Fabrikation der Alkaloids Berlin, 1927, and Ullmann'в Enzyklopädie der technischen Chemie