Amino Acid Tryptophan Indole Alkaloids and Derivatives

Derivative of the Amino Acid Tryptophan Indole Alkaloids and Derivatives 

The presence of an indole nucleus, which is provided by the amino acid tryptophan, is characteristic of this group. Frequently one or two 5 C 

Physostigmine from the Calabar bean Physostigma venenosum (Fig. 130) is an indole alkaloid of simple structure. It is derived from tryptophan via its biogenic amine, tryptamine. 

As far as the biosynthesis is concerned it was soon established that the indole nucleus is derived from the amino acid tryptophan. It was much more difficult to determine the origin of the residual C skeleton but it has been found in recent years that it is furnished by mevalonate or iso-pentenyl pyrophosphate. Thus, in the ergoline alkaloids the indole nucleus is linked with a 5 C unit derived from terpenoid metabolism. 

In the families of the Apocyanaceae, Loganiaceae, Rubiaceae, and Euphorbiaceae, indole alkaloids of complicated structure are found which can be arranged in different groups. We may take reserpine from Rauwolfia serpentina as an example. A sinapic acid residue is present as part of the molecule, in addition to the basic skeleton of tryptophan and two 5 C units (Fig. 130). 

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