Indole alkaloids classification

Other reviews related to this contribution should also be mentioned, in addition to the chapters of this series, which we shall recall later. Some of these deal in general with the problem of classification of indole alkaloids and with chemo-taxonomic investigation (7-5). The chemistry of indole alkaloids is included in the Royal Society of Chemistry s Specialist Periodical Reports and has been extensively reviewed in a one-volume survey edited by J. E. Saxton (6), presenting a reasonably complete, although not exhaustive, picture of the state of the art. Other books on indole alkaloid chemistry treating this area cursorily should also be mentioned (7, 8). Recently, the genus Tabernaemontana was excellently reviewed, particularly with respect to taxonomy, phytochemistry, ethnobotany, and pharmacology (9). 

Fig. 1. Classification of indole alkaloids isolated from Tabernaemontana plants.

Some of the above considerations led to the proposal which has resulted in this compilation of plant species and the classification according to their contained indole alkaloid structural types. The key to this classification is derived from the recent biosynthetic work of Arigoni (2), Battersby 3, 3a), Leete (4), and Scott (5), and their respective co-workers which, in its infancy when Volume VIII of this series was in publication, now presents conclusive evidence concerning the origin of the complex indole alkaloids in plants 5a). 

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).

Table II tabulates the plant species which contain the complex indole alkaloids. The letters in this table correspond to the various structural types as coded in Figs. 2 and 3. Types I, II, and III are the major variations of the Cfl-Ci 0 unit which, in combination with tryptamine, formally elaborate the three significantly different groups of complex indole alkaloids Corynanthe, Iboga, and Aspidosperma. Such initial classification follows the outline set by Battersby [3, 3a) and others (2, 4, 5). The...

A classification of indole alkaloids has been made, based on the number of bonds between the tryptamine and secologanin parts of the skeleton. Another... 

According to the classification of Leeuwenberg (1980), the Rubiaceae may be divided into four subfamilies the Rub-ioideae, Cinchonoideae, Guettardoideae, and Hillioideae. Indole alkaloids of the corynanthean type are the most common in the family. The tribe Cinchoneae of the subfamily Cinchonoideae is the only group to contain alkaloids with a nonrear-... 

Subsequent Reactions of Strictosidine Classification and Structural Types of Indole Alkaloids Formation of the Major Indole Alkaloid Types Summary of Pathways Leading to Major Types of Monoterpene-Derived Indole Alkaloids Chemosystematic and Phylogenetic Application Monoterpenoid Indole Alkaloids of Pharmacologic Significance Vincamine... 

Fig. 34.3. Biogenetic classification of indole alkaloids (Cordell, 1981 used with permission of the author Kompis et al., 1971).

Kompis, I., M. Hesse, and H. Schmid, An approach to the bioge-netic classification of indole alkaloids, Lloydia, 34, 269-291 (1971). 

There is no uniform classification for the A. In the literature divisions according to origin (examples Aconitum, Amaryllidaceae, Aspidosperma, cactus, Catharanthus, Cephalotaxus, Cinchona, coca, Corydalis, curare, Dendrobates, ergot, Erythrina, Iboga, Lycopodium, Maytenus, opium, Rauvol-fia, Senecio, Strychnos, tobacco, Vinca alkaloids, salamander, Solanum, Veratrum steroid alkaloids) in addition to divisions according to chemical structure (examples aporphine, benzylisoquinoline, bis-benzylisoquinoline, berberine, carboline, diterpene, inudazole, indole, indolizidine, isoquinoline, lupinane, macrocyclic, morphine, peptide, / -phenyl-ethylamine, piperidine, purine, pyridine, pyrrolidine, pyrrolizidine, quinoline, quinolizidine, quinucli-dine, spermine, spermidine, steroid, terpene, tro-pane, tropolone alkaloids) are used. 

An understanding of what an alkaloid is will be mentioned in the first section, and in the second section, the aspects of classifying alkaloids on the basis of their biosynthetic origin will be presented. This method will be compared with a classification based on their carbon or heterocyclic skeleton, such as indole, isoquinoline alkaloids, or a classification of the alkaloids based on a chemotaxonomic approach, such as Rutaceae and Apocynaceae alkaloids. A short history of the study of alkaloids and the crude drugs as the origin of various alkaloids, and their relevance in the history of natural products chemistry will be described. Through these discussions, it will be established that the natural products classified as alkaloids relate to our life deeply, and on an everyday basis, as medicines, as dyestuffs, as flavors, as stimulants, and as toxic substances. 

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