Gramine into Tryptophan

In a later paper, Digenis (1969) showed that [methylene- gramine, 

Thus gramine becomes the second example of an alkaloid (after nicotine) that is transformed into an amino acid through catabolic reactions in the plant that produces it. 

Degradation of caffeine occurs in older leaves of Coffea arabica. The roots do not contain caffeine except in the young seedlings (Wanner, 1963), and little is known about the role of roots in catabolism. The degradation process has been studied by Swiss workers (Kalberer, 1964, 1965), and a review of this and other papers as well as some facts are given by Wanner and Kalberer (1966). Experiments have been done with [methyl- C]-labeled as well as with ring-labeled caffeine. 

Thus it would seem that the coffee plant might be capable of degrading caffeine by merely reversing the biosynthetic pathway, a truly remarkable feature The distribution of radioactivity between the identified and uniden- 

In Fig. 6.27b a hypothetical pathway is proposed for the route of caffeine (I) in Cojfea species. This scheme shows two alternative pathways (1) an 

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Figure 6.26. The conversion of gramine into tryptophan, 3-(hydroxymethyl)indole, and indole-3-carboxylic acid (Digenis et al., 1966). Courtesy of the J. Pharmaceutical Science.

When gramine reacts with diethyl nitromalonate, the primary product obtained is diethyl -(3-indolylmethyl)-a-nitromalonate (96.5%), which is converted into tryptophan by partial hydrolysis and decarboxylation, followed by reduction and further hydrolysis.812... 

All the above results are consistent with Wenkert s recent suggestion (57a) that the biological conversion of tryptophan into gramine proceeds by condensation with pyridoxal phosphate (Ilia) with formation of a... 

Table I is a compilation of plant species which contain the simple indole alkaloid types of Fig. 1. As mentioned earlier, the main requirement for the inclusion of a certain simple indole alkaloid into Table I is that it contain a tryptamine unit as a readily distinguishable feature in its structure. That tryptamine is a precursor in the biosynthesis of many of the b, c, d, and e type simple indole bases is yet to be shown although it is felt that future work will prove the correctness of such a view. Gramine, the simplest indole alkaloid, has been included in the tryptamine classification a because it is biosynthetically related to tryptophan cryptole-pine has been likewise included therein although its structural relationship to tryptophan appears more obscure (Volume VIII, Chapter 1, pp. 4, 19). The calycanthine type does not possess a tryptamine structure but it is included in the simple indole alkaloid b classification since most of its congeners are tryptamine derivatives and since it exhibits a close biogenetic relationship to this latter (chimonanthine) type (Volume VIII, Chapter 16). Type d is represented by the small number of the so-called canthin-6-one alkaloids (Volume VIII, pp. 260-252, 497-498). The most recent variation of the simple indole alkaloids is found in the Anacardiaceae family. Its indoloquinolizidine nucleus suggests inclusion with type d on the basis of structural and biogenetic similarity. Finally, simple indole alkaloid type e is composed of the well-defined evodiamine (rutaecarpine) structural form (Volume VIII, Chapter 4).

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