Sequestration, N-Oxidation and Transformation of Plant Pyrrolizidine Alkaloids by the Arctiid Moth Tyria jacobaeae L

Abstract

Larvae o f the arctiid moth Tyria jacobaeae reared on Senecio jacobaea or 5. vulgaris take up and store pyrrolizidine alkaloids (PAs) from their host plants. Individual PAs are taken up without preference. The PA patterns found in the insect bodies correspond to the PA com posi tion o f their host plants. Like plants the insects store PAs as N-oxides, and larvae as well as pupae are specifically able to N -oxidize any tertiary PA. Callimorphine ( 0 9-(2-methyl-2-acetoxybutanoyl)-retronecine), an insect PA well known from several arctiids, was found in pupae and imagines o f Tyria which as larvae had been fed on S. jacobaea. It is accompanied by small amounts o f its isomer 0 7-(2-m ethyl-2-acetoxybutanoyl)-retronecine named isocallimorphine. The callimorphines may well account for 45% o f total PAs found in the insect. Only small amounts o f callimorphine were detected in pupae o f Tyria which as larvae had been fed on S', vulgaris. [l4C]Callimorphine N -oxide was isolated and identified from Tyria pupae which as larvae received [14C]retronecine. It is suggested that Tyria is able to esterify retronecine, derived from hydrolysis o f ingested plant PAs with a necic acid produced by the insect. During metamorphosis the formation o f callimorphine is restricted to the early stage o f pupa tion.

Detoxification of pyrrolizidine alkaloids by the harvestman Mitopus morio (Phalangidae) a predator of alkaloid defended leaf beetles

“…Members of the plant families Asteraceae, Boraginaceae and Fabaceae, which represent the major sources of PA containing plant species, synthesize and store PAs exclusively as N-oxides (Hartmann & Witte 1995;Hartmann 1999). Most PA-sequestering insects also handle and accumulate the alkaloids as N-oxides, including Lepidoptera such as several arctiid moths (Ehmke et al 1990;Hartmann et al 1990;Nickisch-Rosenegk et al 1990;Nickisch-Rosenegk & Wink 1993) and ithomiine butterflies (Trigo et al 1996), Orthoptera such as the aposematic grasshopper Zonocerus (Biller et al 1994) and leaf-beetles of the genus Oreina Hartmann et al 1997;Hartmann et al 1999). Tertiary PAs with certain structural features (e.g., 1-2 double bond and esterification of the allylic hydroxyl group at C-9) are potentially toxic.…”

The two Faces of Pyrrolizidine Alkaloids: the Role of the Tertiary Amine and its N‐Oxide in Chemical Defense of Insects with Acquired Plant Alkaloids

“…Recent investigations revealed that in a number of alkaloid-sequestering species pyrrolizidine alkaloids are exclusively stored as N-oxides, e.g. Arctiidae (Ehmke et al, 1990;Hartmann et al, 1990;Trigo et al, 1993), Ithomiinae (Trigo et al, 1996), Orthoptera (Biller at al., 1994), chrysomelid leaf beetles (Pasteels et al, 1988(Pasteels et al, , 1996Hartmann et al, 1997). These findings indicate that storage of pyrrolizidine alkaloids as N-oxides must be advantageous to the sequestering species.…”

Chemical defense: Bestowal of a nuptial alkaloidal garment by a male moth on its mate

“…Furthermore, the ratio of N-oxide to free base of the two alkaloids varied greatly from moth to moth (on average, the ratio was 1:1). Cosmosoma can evidently convert pyrrolizidine alkaloids metabolically from one oxidation state to the other, as has been shown to be the case for another pyrrolizidine alkaloid-ingesting moth (6).…”