Fabaceae pyrrolizidines

Pyrrolizidine alkaloids have a wide distribution, but are characteristic of certain genera of the Boraginaceae (e.g. Heliotropium, Cynoglossum, and Symphytum), the Compositae/Asteraceae (e.g. Senecio) and the Leguminosae/Fabaceae (e.g. Crotalaria). The pyrrolizidine bases rarely occur in the free form, but are generally found as esters with rare mono- or di-basic acids, the necic acids. Thus, senecionine (Figure 6.18) from Senecio species is a diester of retronecine with senecic acid. Inspection of the ten-carbon skeleton... 

PAs are found widely in the families Asteraceae, Boraginaceae, Fabaceae, and Apocynaceae. About 360 diverse structures have been characterized,23 and these widespread alkaloids are produced by at least 3% of all flowering plants. It is remarkable that one group of animals-the insects-have broken through the formidable alkaloidal defenses represented by the highly toxic pyrrolizidine alkaloids. This evolutionary adaptation has provided a large resource for these insects that is not available to PA-intolerant species, which constitute most of the herbivores. 

Simple bicyclic compounds form a rather small subset of the lupine (or lupin) alkaloids, the overwhelming majority of which have tricyclic or tetracyclic structures based on the quinolizidine motif. These alkaloids are characteristic metabolites of the Papilionoideae, a sub-family of the Leguminosae (Fabaceae), although representative examples have also been isolated from several other plant families. The simple lupine quinolizidines were surveyed in Volume 28 of this treatise (7), while later reviews in Volumes 31 (5) and 47 (9) comprehensively covered all classes of lupine alkaloids, including those containing indolizidine components. Much relevant material is also to be found in the review on the biosynthesis of pyrrolizidine and... 

C,H,5N04, Mr 189.21, mp. I62-I63 C, (c]d +40 (H2O). A. is a polyhydroxylated pyrrolizidine alkaloid (see polyhydroxy alkaloids) from the tree Alexa leio-petala, a south American Fabaceae. The 8-epimer aus-... 

C,H 5Cl2N, Mr 208.13, cryst., mp. 127-129 °C, [aJc +19.6° (CHCi,). An unusual, chlorinated azacyclooctane alkaloid from the Fabaceae genus Lotononis, subsection Rostrata. O. is possibly biogenetically related to the pyrrolizidine alkaloids occurring in the same genus. Ut. Phytochemistry 31, 1029 (1992). - [HS2939 90 CAS 143114-89-0]... 

CigHjjNOs, Mr 351.40, mp. 217°C (207-208°C), [alg -62.4° (CHCI3), [a]o -17.6° (CjHjOH). R. is a pyrrolizidine alkaloid from Asteraceae (Senecio, Erechtites) and some Crotalaria species (Fabaceae). It exists in the plants as the A(-oxide and is highly toxic, causing liver and kidney cancer (see pyrrolizidine alkaloids). 

Pyrrolizidine alkaloids are the leading plant toxins that have deleterious effects on the health of humans and animals. Over 360 different pyrrolizidine alkaloids are found in approximately 3% of the world s flowering plants. These noxious natural products are primarily restricted to the Boraginaceae (many genera), Asteraceae (tribes Senecionae and Eupatoriae), Fabaceae (mainly the genus Crotalaria), and... 

Senecio vulgaris (Asteraceae) is a perennial plant that came to Japan in the Meiji Era (1868—1912) and spread as a naturalized plant aU over the country. In contrast, Senecio pierotii (Asteraceae) is a perennial plant that grows in the swamps of the mountains in Japan. Pyrrolizidine alkaloids, which possess a pyrrolizidine nucleus, were isolated from a number of Senecio plants, inclu-deing S. vulgaris and S. pierotti. These alkaloids are distributed in Senecio plants, and several other genera of plants in the Asteraceae, Boraginaceae, and Fabaceae. Because their principal source is Senecio plants, these pyrrolizidine alkaloids are also known as Senecio alkaloids. 

Study of the pyrrolizidine alkaloids of the Fabaceae, tribe Crotalarieae, suggest that these data are useful for systematic and phylogenetic study of this complex group of legumes (van Wyk and Verdoom, 1990). 

A variety of pyrrolizidine alkaloids and their N-oxides have antitumor activity (Wink, 1993b). Herbal material of Senecio vulgaris (Asteraceae) has been used for hundreds of years as a treatment for cancer. The active compounds have been shown to be senecionine (5) and senecionine N-oxide. Indicine N-oxide (16) from Heliotropium indicum (Boraginaceae) has pronounced antitumor activity. Mono-crotaline (8), from several Crotalaria species (Fabaceae), has similar activity (Blasko and Cordell, 1988 Suffness and Cordell, 1985). Alkylation seems to be involved in the antitumor activity. As the A -oxides cannot serve as enamines and hence cannot be directly involved in alkylation, these compounds should only be active to the extent they are converted to the free bases. At least in the case of indicine iV-oxide (16), this does not appear to be the case (Suffness and Cordell, 1985). 

The pyrrolizidine alkaloids form a toxicologically important group today they occur in some genera of the Fabaceae, Boraginaceae and Asteraceae families. TLC can also be used for identification of these substances. Some hi /-values of the alkaloids occurring most often in these plants are given in Table 76 [200]. 

The already mentioned occurrence of certain alkaloids or alkaloid types in unrelated plants creates some problems for the chemotaxonomist (Matveyev, 1959 Sharapov, 1962). The pyrrolizidine alkaloids, for example, are produced by plants like Crotalaria in Fabaceae, Senecio in Com-positae, Lolium in Glumiflorae, Cynoglossum in Boraginaceae, and Secu-rinega in Euphorbiaceae (Crowley and Culvenor, 1962 Culvenor and Smith, 1967 Culvenor et aL, 1968a,b). The alkaloids derived from the pyridine nucleotide cycle are distributed in unrelated plants. The most common... 

Pyrrolizidine alkaloids are a large and important group of about 250 alkaloids produced by approximately 6000 plant species belonging to 13 families. The most important plants belong to the famflies Boraginaceae, Asteraceae, Heliotropiaceae, Fabaceae and Rham-naceae. Pyrrolizidine alkaloids occur in relatively small amounts (0.1-1% of dry matter) as a complex mixture of more than ten different compounds. Important sources of alkaloids are some herbs and certain fodder plants. 

The structures of a new pyrrolizidine alkaloid, named crotavitelin, isolated from fruits of Crotalaria vitellina, Fabaceae (Papilionoideae) by Bezerra et and six new caffeoyl derivatives possessing a rare octu-losonic acid skeleton isolated from the flower heads of Roman chamomile [Chamaemelum nobile) by Zhao et have been elucidated by the use of NMR including extensive analysis of the proton-proton couplings across two and three bonds. 

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