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There are three main types of alkaloids:

True alkaloids, Pseudo alkaloids and Proto alkaloids

Colchicine is an example of a proto-alkaloid.

Pseudo-alkaloids can be derived from;


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.


  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.
  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
  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;
Tropane, Pyrrolizidine, Pyrrolidine, Benzyl-Isoquinoline, Indole, Quinoline, Pyridine, Quinolizidine, Piperidine

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Georges-Louis Friedli, PgDip., MSc., CH(t)., MACN., PhD.

Last Updated September 1996