Stick insect chemical defenses: potential for useful chemistry (Order Phasmatodea)

Insects make up the most numerous and diverse group of organisms on the planet, yet make up one of the least explored groups of organisms in natural products research (Dossey, A. T., Nat. Prod Rep. 2010, 27, 1737–1757). For about five years our stick insect chemical defense research has led to several seminal discoveries. This presentation will discuss: 1) a brief overview of selected insect natural products with medicinal potential, 2) new findings on the chemistry and biosynthesis of stick insect chemical defenses, and 3) the effects that these compounds have on ants and mosquitoes. To date, the defense chemistry of only 13 of the more than 3,000 species of stick insect species have been analyzed. Our current research program has identified 9 previously known compounds for the first time from phasmids and discovered at least one novel compound, parectadial. For example, we have identified sulcatone from Lopaphus sphalerus and a spiroketal from Asceles glaber, both members of the stick insect lineage Necrosciinae, and demonstrated their behavioral effects on red imported fire ants (Solenopsis invicta) and mosquitoes (Aedes aegypti). Additionally, we have found that the defensive secretion of Anisomorpha buprestoides also contains glucose oxidoreductase activity, demonstrating the potential role of glucosidated precursors in their chemical defense biosynthetic pathways. These results demonstrate that insect chemical biodiversity holds promising potential for studies of biosynthetic pathways and for the discovery of useful natural products.