The Alkaloids and Their Occurrence

It is to be noted that there is a difference in alkaloid content between the two subspecies oi Salamandra, namely, S. maculosa taeniata (S.m.t.) endemic to western Europe and 9. maculosa maculosa (S.m.m.) endemic to south-eastern Europe (3). An outline of the alkaloids and their occurrence in the two subspecies are given in Table I the table emphasizes the two groups of alkaloids which will be discussed in the following sections. 

Volume 15 of this series features four important reviews of research on alkaloids. Chapter 1 by B. S. Joshi, S. W. Pelletier and S. K. Srivastava is the first comprehensive review of the carbon-13 and proton NMR shift assignments and physical constants of diterpene alkaloids and their derivatives. In addition to the catalogue of spectral and physical data, the chapter includes a table of the occurrences of these alkaloids in various plant species, tables containing molecular formulas versus calculated high-resolution mass values, and calculated high-resolution mass values versus the molecular formulas of diterpenoid alkaloids, as well as seven tables summarizing the carbon-13 chemical shifts of various functional groups in diterpenoid alkaloids. 

The monoterpene alkaloids constitute a relatively small group of compounds and their occurrence has been restricted to several species of the genus Kopsia, viz., K. pauciflora, K. macrophylla and K. dasyrachis, from which several new monoterpene alkaloids related to skytanthine have been recently isolated. 

Secophenanthroindolizidine alkaloids and their secophenanthroquinolizidine analogs were last surveyed in Volume 28 of this series (i). A comprehensive review on the occurrence, structural elucidation, biosynthesis, synthesis, and biological activity of the phenanthroindolizidine alkaloids, including their seco variants, was published in 1987 (57P). The topic was also included in several more general reviews on indolizidine alkaloid chemistry 14,19,563). 

New occurrences of the Picralima alkaloids and their derivatives are occasionally reported they are summarized in Table I 2, 8-20a). Ni,-Methylakuammicine has previously been isolated from the bark of Hunteria ehurnea, and it is now shown to be present in the seeds. The occurrence of akuammigine in the leaves of Mitragyna parvifolia collected in the Maharashtra State of India, near Poona, and in Ceylon is of some interest, since it appears not to be present in plants grown... 

Protopine alkaloids are apparently not very common in Aristolochia and however, constrictosme (135), 3-0-methylconstrictosine (136), 3,5-di-O-methyl-constrictosine (137), 5,6-dihydroconstrictosine (138) and 5,6-dihydro-3,5-di-0-methylconstrictosine (139) are the only examples of the protopine alkaloids [280], Their occurrence in Aristolochia was also strictly confined to A. constricta [280]. Protopine alkaloids are usually reported as C-2 substituted on the basis of biogenetic considerations. The unusual absence of C-2 substitution was noticed in the protopines of Aristolochia. 

The occurrence of new furoquinoline alkaloids and their physical properties are indicated in Table VII. N-Methyl-4-quinolones, the so-called isoalkaloids are well known one example is isodictamnine (164), obtained by heating dictamnine with methyl iodide. Isodictamnine, iso-pteleine, isomaculosidine, and isoflindersiamine have now been recognized as constituents of rutaceous species the N-isopentyl alkaloids of Acronychia are also in this category. The alkaloids discussed in this section are grouped in accord with the pattern of oxygenation in the aromatic ring. 

A previous chapter in this series by Price dealing with this subject appeared in 1956 169). The reader is also referred to the standard work in alkaloid chemistry, The Alkaloids [Manske, ed. 16a, 133—135, 147)], and to the authoritative books by Boit 25), Armarego 6), and Dopke 60). A comprehensive review on the quinazoline alkaloids by Johne and Groger appeared in 1970 94). The chemistry of quinazoline alkaloids is being continuously updated in The Alkaloids, a Specialist Periodical Report published by The Chemical Society (London) 78,196). The present review summarizes current knowledge of the occurrence, properties, synthesis, biosynthesis, and biological activity of the quinazoline alkaloids and covers the literature up to the middle of 1983. Table 2 at the end of the chapter lists all presently known quinazoline alkaloids and their sources. 

The three major approaches of ELISA, LC-FLD, LC-MS are likely to continue to be applied to the currently increasing demand for information on occurrence. ELISA techniques are limited in the information provided and as they give variable between-run results, they are therefore best used as semiquantitative tools. Only LC-FLD and LC-MS/MS enable the identification and quantification of the major ergot alkaloids and their epimers. Mass spectrometry is required. LC-MS and LC-MS/MS methods provide unequivocal identification of the alkaloids, and the ability to obtain structural information through collision-induced fragmentation greatly enhances its usefulness for confirmation and elucidation of structure confirmation. LC-MS/MS methods therefore could be preferred to LC-FLD however, the capital costs of equipment are higher. 

Reviews on various aspects of the chemistry of the Veratrum alkaloids have been written by Fieser and Fieser (i), Boit (2), Kupchan (5), and Narayanan (4). In addition, the occurrence of alkaloids in plants of the Veratreae, the classical botanical taxonomy of the Veratreae, and the implications of alkaloid occurrence and structure to the taxonomy of the Veratreae have been reviewed by Kupchan et al. (5). Relationships between structure and hypotensive activity of Veratrum alkaloids and their semisynthetic derivatives have recently been reviewed by Kupchan and Flacke (6). 

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