Stefan Schulz^*

Stefan.schulz@tu-braunschweig.de

Institute of Organic Chemistry, Technische Universität Braunschweig, Braunschweig, Germany.

Compared to plants, microorganisms, or fungi, secondary metabolites of terrestrial animals have been less often investigated, except perhaps for insects. One of those neglected groups are Collembola, important soil-dwelling arthropods often occurring in large numbers. They constitute a sister lineage to the Insecta, but the common precursor dates back to more than 450 mya. This long time leads to surprising differences in the secondary metabolites of these lineages that will be discussed. We focused our studies on three aspects, which are important in Chemical Ecology: epicuticular lipids, defense compounds, and volatile signals. Several difficulties must be overcome when working with these animals, namely their small size, difficult and slow rearing, and often uniform appearance. However, with trace analytical techniques and chemical synthesis, we could show that springtails often rely on the terpenoid biosynthetic pathway for both epicuticular lipids and signals. For defense, compound classes are produced that are not known from other genera.

While the defense chemistry of certain frog lineages is well explored, their chemical communication systems are rarely investigated. Certain groups developed gular or femoral glands that are likely used in chemical communication. Our results show that batrachopolyenes, unusual hydrocarbon steroids with a nor-A-ring, are found in several distinct lineages, suggesting a common precursor. In contrast, highly diversified macrocyclic lactones are used mainly within the Mantellinae and seem to represent a derived compound class. Related lactones occur in various sources, such as insects, bacteria, or mammals, indicating a preferred structural motif that was introduced several times independently during evolution.

We report here on the identification of these compounds, which proved quite difficult due to the small amounts of material available or conservation restrictions. Therefore, GC/MS, GC/IR, and various other methods were used for structure confirmation, including total synthesis, because NMR analysis was only possible in some cases.

Keywords: Steroids, macrocyclic lactones, GC/MS, terpenoids, total synthesis

 
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