|Le Blanc, Blaise|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 20, 2008
Publication Date: December 20, 2008
Citation: Le Blanc, B.W., Boue, S.M., Hoffman, G.D., Deeby, T.A., Mccready, H.D., Loeffelmann, K.L. 2008. Cyclodextrins as Carriers of Monterpenes into the Hemolymph of the Honey Bee (Apis mellifera) for Integrated Pest Management. Journal of Agricultural and Food Chemistry 56(18), 8565-8573. Interpretive Summary: Thymol and carvacrol (monterpenes), which are components of oil of thyme and origanum, respectively, were encapsulated with beta cyclodextrin. Beta cyclodextrin served as a carrier to carry the monterpenes into the hemolymph of honey bees (Apis mellifera) in effort to repel Varroa mites, which thrive by ingesting bees hemolymph. The toxicity of the characterized complexes and the cyclodextrin were reported and the levels of thyme and carvacrol were quantitated.
Technical Abstract: The Varroa mite (Varroa destructor), is becoming ubiquitous worldwide and is a serious threat to honey bees. The cultivation of certain food crops are at risk. The most noted acaricides against Varroa mites are with tau-fluvaninate and with coumaphos, but the mites are showing resistance. Since these insectidices are used in the proximity of honey, it is desirable to use natural alternatives. Monoterpenoids such as thymol and carvacrol, that are constituents of oil of thyme and oil of origanum, show promise as acaricides against the Varroa mite, but the delivery of these compounds remains a challenge due to the low water solubility and uncontrolled volatility. Beta cyclodextrin inclusion complexes of thymol oil of origanum and carvacrol were prepared on a preparative scale. Competitive binding was studied by fluorescence spectroscopy by using 6-p-toluidinylnaphthalene-2-sulfonate as a fluorescent probe. The complexes were characterized and the competitive binding described by 1H and 13C nuclear magnetic resonance spectroscopy chemical shifts. The toxicity of Beta cyclodextrin and the prepared complexes in enriched sucrose syrup were studied by conducting caged honey bee (Apis mellifera) feeding trials. After the first and second weeks of feeding, hemolymph and gut tissue samples were acquired from the caged bee study. The levels of thymol and carvacrol were quantified by solid phase micro-extraction gas chromatography mass spectroscopy, by our optimized procedure. High (mM) levels of thymol and carvacrol were detected in bee tissues without any imposed toxicity to the bees, in effort to deter Varroa mites from feeding on honey bee hemolymph.