Pyrrolizidines quinolizidine alkaloids

Quinolizidine alkaloids are non-toxic to the legumes which produce them. On the other hand, the quinolizidine alkaloids can be toxic and in some cases very toxic to other organisms. The biotoxicity of alkaloids has for some time been considered to be connected with their bitter taste" ° ". The quinolizidine alkaloids are certainly bitter in taste to humans. However, not all alkaloids are. Literature states that some pyrrolizidine and indolizidine alkaloids are not bitter in their pure forms" Furthermore, there are many non-alkaloid compounds, such as flavonoids, that are bitter in taste but non-toxic. Therefore, although quinolizidine alkaloids are bitter, the connection between biotoxicity and bitter taste is not absolute. 

Acute toxicity of berberine and thebaine Acute toxicity of some quinolizidine alkaloids Acute toxicity of some pyrrolizidine alkaloids Some narcotics and their derivatives. 

Dreyer, D. L., Jones, . C. and Molyneux, R. L. (1985). Feeding deterrency of some pyrrolizidine, indolizidine, and quinolizidine alkaloids towards pea aphid (Acryrthosiphon pisum) and evidence of phloem transport of indolizidine alkaloid swainsonine. Journal of Chemical Ecology 11 1045-1051. 

Robins DJ (1995) Biosynthesis of pyrrolizidine and quinolizidine alkaloids. The Alkaloids, Chemistry and Pharmacology (ed Cordell GA) Vol 46. Academic, San Diego, pp 1-61. 

Hyoscyamine, scopolamine, and other tropane alkaloids (AA) acetylheliosupine and some other pyrrolizidine alkaloids arecoline (A) berbamine, berberine, and other isoquinoline alkaloids dicentrine and other aporphine alkaloids strychnine, brucine cryptolepine (AA) sparteine and other quinolizidine alkaloids (A) pilocarpine (A) emetine himbacine and other piperidine alkaloids (A) imperialine (AA) muscarine (A)... 

A comparable situation to insect specialists can be found in parasitic and hemi-parasitic plants, another example of multitrophic interactions. In several instances it can be shown that the parasites can tap the xylem or phloem of their host plants and sequester the host alkaloids into their own system [2,31]. The parasites would gain chemical defense against herbivores by such a process (Table 1.4). In Osyris alba it can be shown that plants exist that can sequester the alkaloids of more than one host plant that is, pyrrolizidine and quinolizidine alkaloids [32]. The situation of Lolium is even more complex [33]. If the grass Lolium temulentum is infected by an endophytic... 

Figure 7.8 (Continued) (c) pyrrolizidine and quinolizidine alkaloids and are highlighted in colour. (See Plates 10-12 in colour plate section.)...

Pyrrolizidine alkaloids, chemistry and toxicology of 86MI9. Quaternary benzo[c]phenanthridine alkaloids 90CCC2840. Quinolizidine alkaloids 87WCH393. 

II.1. PYRROLIZIDINE, PYRIDINE, PIPERIDINE AND QUINOLIZIDINE ALKALOIDS Chapter 4... 

Both castanospennine and swansonine occur in some legume plants, such as Castanospermum australe and Swainsom canescens, respectively. They are hybrid molecules compounded of pyrrolizidine and quinolizidine alkaloids and have shown some resistance to the AIDS virus. Certainly, the above-mentioned alkaloids are also toxic for animals. 

Many species of Castilleja (Scrophulariaceae) contain iri-doid monoterpenes (Arslanian et al, 1985) as well as pyrrol-izidine, quinolizidine, and monoterpene iridoid alkaloids (Stermitz et al., 1986a). Both pyrrolizidine and quinolizidine alkaloids appear to be taken from the hosts of these hemipar-asitic plants see Chapter 30). The larvae of Platyptilia pica (Pterophoridae) excrete but do not sequester iridoids. The adult moths contained rhexifoline, an iridoid monoterpene alkaloid (Stermitz et al, 1986a). 

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