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Title: Defensive Spiroketals from Asceles glaber (Phasmatodea): Absolute Configuration and Effects on Ants and Mosquitoes

Author
item DOSSEY, AARON - University Of Florida
item WHITAKER, JOHN - Scripps Institute
item DANCEL, MARIA CHRISTINA - University Of Florida
item Vander Meer, Robert - Bob
item Bernier, Ulrich
item GOTTARDO, MARCO - University Of Siena
item ROUSH, WILLIAM - Scripps Institute

Submitted to: ACS Chemical Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2012
Publication Date: 9/14/2012
Citation: Dossey, A., Whitaker, J.M., Dancel, M.A., Vander Meer, R.K., Bernier, U.R., Gottardo, M., Roush, W.R. 2012. Defensive Spiroketals from Asceles glaber (Phasmatodea): Absolute Configuration and Effects on Ants and Mosquitoes. ACS Chemical Biology. 38(9): 1105-1115.

Interpretive Summary: Insects are the largest and most diverse group of organisms on earth, with over 1,000,000 species identified to date. Stick insects (“walkingsticks”) are well known for and name derived from their use of camouflage as a primary line of defense from predation. However, many species also possess a potent chemical defense spray. This spray is likely to be released as a predator deterrent and could function as a repellent. In the present study, Scientists from the Imported Fire Ant and Household Insect, and the Mosquito and Fly Research Units at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, FL, Scripps Florida, Jupiter, FL; University of Siena, Siena, Italy; and University of Florida, Gainesville, FL identified the major compound produced by stick insect, Asceles glaber, demonstrated the effect of this compound on mosquitoes and fire ants using several bioassays, and discussed how these results provide evidence of the utility stick insects possess in natural product research. This work contributes to the demonstration of the chemical biodiversity which exists in insect chemical defenses and support for stick insects as model organisms for insect chemical defense studies.

Technical Abstract: Recently we discovered that the defensive spray of Asceles glaber, a stick insect native to Thailand, contains two spiroketals (major: 2(S)-(-)-(E,E)-2- methyl-1,7-dioxaspiro[5.5]undecane and minor: 2-ethyl-1,6-dioxaspiro[4.5]decane) and glucose. In this report we: 1) illustrate the identification of spiroketals and glucose in the defense spray of A. glaber using NMR, GCMS, and comparison with a synthetic reference sample, 2) provide the elucidation of the absolute configuration of the major spiroketal in that defense spray, 3) quantify the concentration of the major spiroketal in A. glaber defense spray, 4) demonstrate the effect of both enantiomers of the major A. glaber defensive spiroketal on both fire ants and mosquitoes, 5) propose a mechanism for stick insect chemical defenses, 6) discuss a potential role of glucose in stick insect defense sprays, 7) note the possible significance of the chemistry of defense sprays in the taxonomic relationships among the Phasmatodea and 8) discuss how these results provide evidence of the utility stick insects possess in natural product research. This work contributes to the demonstration of the chemical biodiversity which exists in insect chemical defenses and support for stick insects as model organisms for insect chemical defense studies.