Alkaloids of Plant Origin

Alkaloids are most widely distributed among flowering plants and rarely occur in animals, simple vascular plants, mosses, ferns, fungi, and algae. Indole alkaloids are no exception to this general observation. 

Since tryptophan is recognized as a main constituent of plant proteins and as a common biogenetic precursor of the complex indole alkaloids, the wide occurrence of tryptamine derivatives in the plant kingdom is not unexpected. The presently known cases of these simple indole alkaloids have been ones in which a tryptamine unit formally appears as a slightly modified structure (e.g., by oxidation or methylation), as a cyclized form or a dimeric variation thereof, or as a modification which incorporates short carbon chains (e.g., C4, C2) or a simple aromatic structure (anthranilic acid) respectively. The great majority of the simple indole alkaloids are confined to the dicotyledon plants. 

It is reasonable then that the complex indole alkaloids also mainly inhabit the dicotyledones. Moreover, as has been pointed out by Le Men and Taylor 6) they occur most frequently in the Apocynaceae, Logani-aceae, and Rubiaceae plant families. A few representatives of this remarkable group have also been found in phylogenetically more remote families such as Annonaceae, Euphorbiaceae, and Sapotaceae. The questionably related Alangiaceae and Icacinaceae families are the most recent additions to the list of plants which contain complex indole alkaloids. The structural features of this class are a tryptamine unit 

Until such time when the biosynthetic pathways of the complex indole alkaloids have been completely defined their full taxonomic value cannot be appraised. However, a number of recent reviews (7, 8) indicate that chemotaxonomic considerations in this area have been aided by the rapid progress made in the chemistry and biosynthesis of the various indole alkaloids. Furthermore, the latter two disciplines have benefited from the former in the search for new alkaloids and in the elucidation of biosynthetic pathways. In the future it is expected that many advances in indole alkaloid chemistry will often arise as a result of the convergence of biochemical and chemical research efforts (9). 

The present compilation derives a great deal of its content from previous tabulations and reviews. Extensive use has been made of Volumes II, III, V, VII, and VIII of this treatise, the comprehensive volume of Boit (10), and the tables of Willaman and Schubert (11), Hesse (12), and Holubek and Strouf (12a). Hesse s useful publication covered the literature to the end of 1963. The present tables extend the coverage of known indole alkaloids through May, 1967 Chemical Abstracts with an inclusion of some references from more current major journals. 

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The isolation of atropine, scopolamine, and cocaine occurred long before the development of modern analytical techniques. Gas chromatography was the first instrumental technique available in the field of separation science and thus it is not surprising that these alkaloids were firstly analyzed by GC despite their low volatility. With the advent of capillary columns and the proliferation of various sample introduction and detection methods, GC has evolved as the dominant analytical technique for screening, identification, and quantitation of tropane alkaloids of plant origin as well as in biological fluids. The state-of-the-art of GC analysis of tropane alkaloids has been the subject of two comprehensive reviews [45,58]. We shall therefore mainly focus on publications which have appeared since 2002. 

The Table summarizes recent isolation and structural elucidation work on quinoline and furoquinoline alkaloids of plant origin. The structure of folisine (4) from Haplophyllum foliosum was confirmed by synthesis. Heating the methiodide of dubinidine (11) yielded folisine. The alkaloid distribution in H. suaveolens was extensively examined in leaf, stem, fruit with seeds, and root kokusaginine (1 R = = OMe, R = H) was found to be the major component in all... 

Keeler, R.F. 1989. Quinolizidine alkaloids in range and grain lupins, in Cheeke, P.R., Ed., Toxicants of plant origin, Vol. I Alkaloids, CRC Press, Boca Raton, pp. 133-168. 

Soaking plants parts in alcohol (ethanol) creates a tincture. In this process, pharmacologically active constituents of the plant are extracted by the alcohol. Tinctures do not contain the complete spectrum of substances that exist in the plant or crude drug, only those that are soluble in alcohol. In the case of opium tincture, these ingredients are alkaloids (i.e., basic substances of plant origin) including morphine, codeine, narcotine = noscapine, papaverine, narceine, and others. 

Arctiid moths are also capable of synthesizing their own PAs from a necine base of plant origin and a necic acid synthesized from isoleucine in their own metabolism. Callimorphine, a PA not produced by plants, is synthesized by many arctiid moths and is sequestered as a defensive compound after re-esterification of retronecine of plant origin. Creatonotine, another insect PA, is produced by adults of C. transiens by esterifying ingested retroncine with a distinctive necic acid. These moths are unique in adding de novo-synthesized PAs to plant-derived alkaloids as part of their defensive arsenal. 

CHEEKE, P.R., Pyrrolizidine alkaloid toxicity and metabolism in laboratory animals and livestock, in Toxicants of Plant Origin, Vol. 1, (P.R. Cheeke, ed.), CRS Press, Boca Raton. 1989, pp. 1-22. 

Gas chromatography of cocaine of plant origin has mainly involved the analysis of the coca plant [77-79]. Identification and quantitation GC methods of minor naturally occurring tropane alkaloids in illicit cocaine samples have also been reviewed [80]. Moore et al. presented an in-depth methodology for the analysis of the coca plant by GC-FID, GC-ECD, and GC-MS for the identification of alkaloids of unknown structure [81]. Recently, Casale et al. [82] have analyzed the seeds from Erythroxylum coca for their alkaloidal content. Several tropane alkaloids were detected and characterized and it appeared that methylecgonidine (MEG) was the primary constituent and not an analytical artifact. 

The chemistry of jS-carbolines of plant origin (5b-f) as well as the history and ethnopharmacological background of these alkaloids have been reviewed (5d). The chemistry of the mammalian j3-carbolines relevant to synthesis and further chemical transformation, however, has never been presented. With the information detailed in Figs. 4-7, and in Fig. 8 for the preparation of optically active representatives, this gap has now been filled. 

While there may be phylogenetic reasons for particular distributions of the polyhydroxylated alkaloids in plants, caution should nevertheless be exercised in using the presence of these compounds as taxonomic markers. One reason is that these alkaloids can be released into the soil by producer plants and micro-organisms from where some, such as DMDP and castanospermine can be readily taken up and accumulated in plant tissues of completely unrelated neighbouring species. It may also be the case that micro-organisms (Rhizobium, other rhizosphere organisms, or endophytes) closely associated with specific plants may also produce polyhydroxylated alkaloids which could then be mistakenly considered of plant origin. 

Alkaloid—/K nitrogen-based chemical, usually of plant origin, also containing oxygen, hydrogen, and carbon. Many are very bitter and may be active if ingested. Common alkaloids include nicotine, caffeine, and morphine. 

Caffeine belongs to a large class of compounds known as alkaloids. These are of plant origin, contain basic nitrogen, often have a bitter taste and complex structure, and usually have physiological activity. Their... 

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