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'''ALKALOIDS'''

The basic unit in the biogenesis of the true alkaloids are AMINO ACIDS. The non-nitrogen containing rings or side chains are derived from TERPENE units and / or ACETATE, while METHIONINE is responsible for the addition of methyl groups to nitrogen atoms.

'''Alkaloids''' are highly reactive substances with biological activity in low doses.

DEFINITION

1. Contains nitrogen - usually derived from an amino acid.
2. Bitter tasting, generally white solids (exception - nicotine is a brown liquid).
3. They give a precipitate with heavy metal iodides.
* Most alkaloids are precipitated from neutral or slightly acidic solution by Mayer's reagent (potassiomercuric iodide solution). Cream coloured precipitate.
* Dragendorff's reagent (solution of potassium bismuth iodide) gives orange coloured precipitate with alkaloids.
* Caffeine, a purine derivative, does not precipitate like most alkaloids.
4. Alkaloids are basic - they form water soluble salts. Most alkaloids are well-defined crystalline substances which unite with acids to form salts. In plants, they may exist
* in the free state,
* as salts or
* as N-oxides.
5. Occur in a limited number of plants. Nucleic acid exists in all plants, whereas, [[morphine]] exists in only one plant species.

Alkaloids can be classified;

* in terms of their BIOLOGICAL activity,
* CHEMICAL structure (nucleus containing nitrogen),
* BIOSYNTHETIC pathway (the way they are produced in the plant).

[[sv:Alkaloider]]
[[es:Alcaloides]]

Alkaloids - Revision history

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