Page 70 - phytochemistry II -pharmD general

Indole alkaloids

The indole alkaloids comprise a very important class of medicinally valuable
alkaloids; and from those plants containing indole alkaloids, several useful drugs
have been derived and used for centuries. As, for example the drug Ergot; the
oxytocic effect of which has been well known for centuries, before its official
recognition in the mid1800s, and well before the isolation and identification of its
active alkaloidal constituent.

Of the medicinally important representatives of the indole class, are:

1- The Ergot alkaloids 2- Strychnos alkaloids

3- Physostigma alkaloids 4- Rauwolfia alkaloids

5- Yohimbe alkaloids 6- Vinca or Catharanthus 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.

Indole

N
H

NH2 NH2
H2C CH2 H2C CH

COOH

N Tryptamine N Tryptophane
H
H

The clavine alkaloids of Ergot as well as the lysergic acid moiety of all Ergot
alkaloids are products of condensation of tryptophan with an isoprenyl moiety;
where the two carbon side chain of trptophan together with the C5 prenyl moiety
provided rings C and D.

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