Acquired and Partially De Novo Synthesized Pyrrolizidine Alkaloids in Two Polyphagous Arctiids and the Alkaloid Profiles of Their Larval Food-Plants

Abstract

The profiles of pyrrolizidine alkaloids (PAs) in the two highly polyphagous arctiids Estigmene acrea and Grammia geneura and their potential PA sources in southeastern Arizona were compiled. One of four species of Boraginaceae, Plagiobothrys arizonicus, contained PAs; this is the first PA record for this plant species. The principle PA sources are Senecio longilobus (Asteraceae) and Crotalaria pumila (Fabaceae). The known PA pattern of S. longilobus was extended; the species was found to contain six closely related PAs of the senecionine type. Three novel PAs of the monocrotaline type, named pumilines A-C, were isolated and characterized from C. pumila, a species not studied before. The pumilines are the major PAs in the seeds, while in the vegetative organs they are accompanied by the simple necine derivatives supinidine and as the dominant compound subulacine (1beta,2beta-epoxytrachelanthamidine). In both plant species, the PAs are stored as N-oxides, except C. pumila seeds, which accumulate the free bases. Great variation in PA composition was observed between local populations of C. pumila. The PA profiles were established for larvae and adults of E. acrea that as larvae had fed on an artificial diet supplemented with crotalaria-powder and of G. geneura fed with S. longilobus. In both experiments, the larvae had a free choice between the respective PA source and diet or food plants free of PAs. The profiles compiled for the two species reflect the alkaloid profiles of their PA sources with one exception, subulacine could never be detected in E. acrea. Besides acquired PAs, insect PAs synthesized from acquired necine bases and necic acids of insect origin were detected in the two arctiid species. These insect PAs that do not occur in the larval food sources accounted for some 40-70% (E. acrea) and 17-37% (G. geneura) of total PAs extracted from the insects. A number of novel insect PAs were identified. Plant-acquired and insect PAs were found to accumulate as N-oxides. The results are discussed in relation to specific biochemical, electrophysiological, and behavioral mechanisms involved in PA sequestration by arctiids.

Scientific Opinion on Pyrrolizidine alkaloids in food and feed

“…Because PAs and PANOs do not show characteristic ultraviolet (UV) spectra (exhibiting only a non-specific UV-maximum of 214 nm), simple UV detection is of limited value. However, LC techniques are frequently and successfully used to purify PAs for structural identification including the enantioseparation of isomers like intermedine/lycopsamine (Hartmann et al, 2004;Pawar et al, 2010). Recently, a HPLC approach was published where retronecine-type PAs are converted by pre-column derivatisation to a common core structure derivative (7-methoxy-1-methoxymethyl-6,7-dihydro-5H-pyrrolizine) and analysed by reverse phase HPLC with photodiode array detection (HPLC-diode array detection (DAD) (absorption maximum at 223 nm)).…”

Eggs of cabbage root fly stimulate conspecific oviposition: Evaluation of the activity and determination of an egg-associated compound

“…It seems unlikely that it is absorbed directly from the plant as only a small proportion of eggs is in contact with the host. The results suggest that it may be of female origin, either by direct synthesis or via sequestration of host plant defences (Dobler et al, 1998;Barker et al 2002;Hartmann et al, 2004) or both as found for the monoterpene myrcene in the bark beetle, Ips pini (Seybold & Tittiger, 2003) or from male origin at time of mating (Bali et al, 1996;Gillot, 2003).…”

Pyrrolizidine Alkaloids in the Pericopine MothScearctia figulina(Erebidae: Arctiinae): Metabolism and Chemical Defense

“…14,15,[27][28][29] We assigned the absolute stereochemistry of PAs based only in retention index of chiral PAs reported in the literature. 20,27 Chemical defense of Scearctia figulina: predation bioassays…”