Page 76 - Phytochemistry 2 (06-PG 605)

Indole alkaloids

The indole alkaloids comprise a very important class of
medicinally valuable alkaloids. As, for example the drug Ergot; the
oxytocic effect of which has been well known for centuries, before
its official recognition, and well before the isolation and
identification of its active alkaloidal constituents.

Also, Nuxvomica, another indole alkaloids-bearing drug, was
well known in Folklore medicine long ago, before being medicinally
used in Europe in the sixteenth century. Its principle active
alkaloidal principle, strychnine, has been isolated and identified.

Of the medicinally important representatives of the indole class,

are: 2- Strychnos alkaloids
1- The Ergot alkaloids 4- Rauwolfia alkaloids
3- Physostigma alkaloids 6- Vinca or Catharanthus alkaloids
5- Yohimbe alkaloids
7- Gelsemium alkaloids.

Almost all these alkaloids are biogenetically derived from the

amino-acid tryptophan. So, they are also referred to“ Tryptophan-

derived alkaloids”.

Being derivatives from tryptophan, most of the indole

alkaloids contain two nitrogen atoms in their molecule.

Some subclasses of indole alkaloids, arise from

condensation of tryptophan with a C5 (prenyl) moiety, provided by

mevalonic acid, and some others are produced through

condensation of tryptophan and a C10 (geranyl) moiety, to give

higher molecular weight and more complex alkaloidal structures.

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