Alkaloid

The alkaloids are organic molecules heterocyclic nitrogenized of natural origin being able to have a pharmacological activity.

This name derives from the word Alcalin; in the beginning, the term was employed to describe any Base of Lewis containing a nitrogenized heterocycle (or improperly a amine). Because of the electronic doublet not binding nitrogen the alkaloids are regarded as bases of Lewis.

One finds alkaloids, as a secondary metabolites, mainly at the Végétaux, the Champignon S and some animal groups very few. Usually the alkaloids are derivatives of the amino-acid .

The mode of extraction is very variable according to the nature of alkaloid; but two diagrams of extraction typically are found: by a non-polar solvent in alkaline medium or by a polar solvent in acid medium (of Brönsted).

The alkaloids have the property to form salt S and to be bitter.

The characterization of the presence of alkaloid can be done by precipitation using:

  • Reactive silicotungstic: reagent of Bertrand.
  • Reactive phosphotungstic: reagent of Scheibler.
  • Reactive phosphomolybdic: reagent of Try-Sonenschein.
  • Reactive phosphoantimonic: Schulze reagent.
  • Iodide of potassium: reagent of Bouchardat.
  • Tétraiodomercurate of potassium: reagent of Valser-Mayer.
  • Iodobismuthate of potassium: reagent of Dragendorff.
  • Iodoplatinate of potassium.
  • Picric acid.
  • Tannins.
Many other methods as the Chromatographie are also employed to identify and proportion the molecule.

Although many alkaloids are Toxique S (like the Strychnine or the conitine), some are employed in medicine for, for example, their properties Analgésique S (like the Morphine or the Codéine) or within the framework of protocols of sedation (anesthesia) often accompanied by Hypnotique S.

There exists a type of alkaloids containing two nitrogen atoms in the aromatic nucleus and which is not natural origin, it is the group of the Pyrazoles.

Classification of alkaloids

They a long time were categorized and named according to the plant or of the animal from which they were insulated.

But one usually categorizes them according to their chemical structure.

Classification according to the chemical structure

  • Group of the Pyrrolidine S : Hygrine, Cuscohygrine, Nicotine.

  • Groupe of the Bétaïne S (compounds of quaternary Ammonium, they are not alkaloids with the clean direction, even if regularly classified like such): Muscarine, Choline, Neurine.

  • Groups of the Pyrazole S :

See too

Random links:Circus Alexandro Klising | Rosazza | 1948 in Canada | Durham (North Carolina) | Castillo-Gaztelu