Direct evidence for membrane transport of host-plant-derived pyrrolizidine alkaloid N-oxides in two leaf beetle genera
| Autor: | Ingo Narberhaus, Susanne Dobler, Thomas Hartmann, Claudine Theuring, Till Beuerle, Ulrich Papke |
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| Rok vydání: | 2004 |
| Předmět: |
Pyrrolizidine alkaloid
Biochemistry Gas Chromatography-Mass Spectrometry Cyclic N-Oxides chemistry.chemical_compound Eating Glucosides Hemolymph Botany Animals Ecology Evolution Behavior and Systematics Pyrrolizidine Alkaloids Membranes biology Biological Transport General Medicine biology.organism_classification Oreina Longitarsus Coleoptera chemistry Isotope Labeling Pyrrolizidine Senecionine Oxidation-Reduction Longitarsus jacobaeae Oreina cacaliae Leaf beetle |
| Zdroj: | Journal of chemical ecology. 30(10) |
| ISSN: | 0098-0331 |
| Popis: | The chrysomelid leaf beetles Longitarsus jacobaeae, Oreina cacaliae, and O. speciosissima sequester pyrrolizidine alkaloids from their asteracean host plants and store them as nontoxic N-oxides. Previous analyses showed that Longitarsus is able to N-oxidize protoxic tertiary PAs, but did not resolve in which form N-oxides are taken up. For Oreina, beetles seem able to directly transmit the polar PA N−oxides from the gut into the hemolymph and prevent any reduction of them in the gut yielding protoxic free bases. Here, we confirm the predicted direct uptake of PAs as N−oxides by Oreina, and elucidate the situation for Longitarsus by applying double-labeled [14C]senecionine [18O]N−oxide as tracer. The beetles were fed with the tracer and subsequently senecionine N−oxide was recovered from the defensive secretions (Oreina) and beetle extracts (Longitarsus), purified by HPLC, and submitted to ESI-MS, GC-MS, and analysis of the specific radioactivity. The 18O-label is retained without any loss in the labeled senecionine N−oxide recovered from the two Oreina species. Analysis of the Longitarsus experiment was complicated by a contamination of the HPLC-purified senecionine N−oxide with a second compound, identified as a dihydrosenecionine N−oxide by high-resolution CID analysis. The dihydrosenecionine N−oxide, probably the 15,20-dihydro derivative, constitutes a major idiosyncratic senecionine metabolite present in the beetle. The recovered senecionine N−oxide retained 74% 18O-label. The remaining 25% is mostly due to loss of 18O by reduction and subsequent re-N−oxidation. The experiments confirm for both beetle genera a direct uptake of the polar nontoxic PA N−oxides, which requires specific membrane carriers. Accumulation of detrimental free base PA is prevented by glucosylation (Oreina) or N−oxidation (Longitarsus). |
| Databáze: | OpenAIRE |
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