Pyrrolizidine alkaloids localization

At overwintering sites of the monarch butterfly [Danaus plexippus) in Mexico, only one of the three local mouse species, Peromyscus melanotis, actually feeds on the butterflies. The monarchs contain cardiac glycosides (CG) and pyrrolizidine alkaloids (PA). All three species of mice have similarly low avoidance thresholds to PA (specifically, monocrotaline). But P. melanotis is less sensitive to CG (specifically, digitoxin) than the other two, Reithrodontomys sumichrasti and Peromyscus aztecus. Laboratory tests indicate that PA is toxic to young mice. 

Fig. 2. Alkaloid biosynthetic pathways are associated with a diverse variety of cell types. The tissue-specific localization (shaded) of enzymes and/or gene transcripts are depicted for the biosynthesis of tropane alkaloids in Atropa belladonna and Hyoscyamus niger roots (A), monoterpenoid indole alkaloids in Catharanthus roseus leaves (B), pyrrolizidine alkaloids in Senecio vernalis roots (C), pyrrolizidine alkaloids in Eupatorium cannabinum roots (D), benzyl-isoquinoline alkaloids in Papaver somniferum vascular bundles (E), and protoberberine alkaloids in Thalictrwn flamtm roots (F).

HSS, the first committed pathway enzyme, was localized to the root endo-dermis and cortex adjacent to the phloem in S. vernalis (Fig. 2C), which might reflect a functional accommodation for systemic transport of pyrrolizidine alkaloids to the stem (259). However, HSS was found throughout the root cortex in E. cannabinum (Fig. 2D), which is a member of the Asteraceae family along with S. vernalis (170). In contrast to the general monophyletic origin of BA biosynthesis (16),... 

The main drawback of these solvent suppression procedures is that the analyte signals localized under the solvent resonances will also be suppressed and thus the whole range of H-NMR signals are not directly observable. This can be a major drawback when dealing with unknown constituents. In order to detect all analyte signals, one alternative is to carry out the solvent suppression in two independent solvent systems such as MeCN-D20 and MeOH-D2O. Such an approach is shown for the analysis of hepatotoxic pyrrolizidine alkaloids in the crude... 

Quinolizidine alkaloids are derived from lysine. Studies with labeled precursors indicate that a symmetrical intermediate, cadaverine (20), is involved in their formation (Herbert, 1988 Kinghom and Balandrin, 1984 Leete, 1983 Spenser, 1985), although no intermediate comparable to the dimeric form plays a role in the formation of pyrrolizidine alkaloids is involved (Spenser, 1985). Much recent information is based on cell suspension cultures of Lupinus polyphyllus, Baptisia australis, and Sarothamnus scoparius (all Faba-ceae). Lysine decarboxylase is localized in leaf chloroplasts (Wink 1987 Wink and Hartmann, 1982,1984) the presence of a diamine oxidase does not appear to be involved. Lysine decarboxylase is found in all parts of Lupinus plants. 

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