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Chemistry of the Androconial Secretion of the Ithomiine Butterfly Oleria onega
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Edité par CCSD ; Springer Verlag -
International audience. Ithomiine butterflies use pyrrolizidine alkaloids (PAs) as precursors for malepheromones, such as dihydropyrrolizines or lactones. In contrast to most other ithomiine genera,none of these compounds have ever been detected in Oleria species. The absence of thesecompounds is thought to be the result of limited access to PA-containing plants. Here weinvestigate the contents of the androconia of Oleria onega caught in the wild when PA containingplants were abundant. Although the PA lycopsamine was detected in the hairpencils, none of theother known PA-derived compounds were present. Instead, the unsubstituted core of the PA necinebase, 1-methylene-1H-pyrrolizine (13), a very unstable compound, was found. The identity of thiscompound was proven by synthesis. Although its formation in nature appears very likely, 13 isalso formed during GC analysis of PAs, making its natural formation ambiguous. Nevertheless, itsreactivity makes it a good candidate for a signaling compound, because its rapid degradation canbe used for transporting spatial and time information. In addition, several other compounds, likelyused in intraspecific communication, were identified. All these compounds are reported for thefirst time as natural products or from insects. These include 9-hydroxynonanoic acid (21) and (Z)-9-hydroxy-6-enoic acid (18), as well as their condensation products with 11-hexadecenoic- andoctadecenoic acids. Furthermore, self-condensation products, such as (Z)-9-[(9-hydroxynon-6-enoyl)oxy]- and 9-[(9-hydroxynonanoyl)oxy]nonanoic acid and non-6-enoic acids (35, 36, 38, 40)were identified, together with the known compounds 2-heptadecanol (39) and 6,10,14-trimethylpentadecan-2-ol (37). In summary, O. onega appears to lack enzymes to producedihydropyrrolizines. In stark contrast to other ithomiine genera, a unique blend of oxidized fattyacids seems to be used instead.
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