Submitted to: Journal of Chemical Ecology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/3/2011
Publication Date: 5/26/2011
Citation: Jang, E.B., Siderhurst, M.S., Khrimian, A. 2011. Di- and Tri-flourinated analogs of methyl eugenol: attractiveness to and metabolism in the oriental fruit fly, bactrocera dorsalis (hendel). Journal of Chemical Ecology. 37:553-564. Interpretive Summary: The oriental fruit fly is a serious pest of agriculture in the tropics. Methyl eugenol, a natural product, is highly attractive to this pest. In this research we looked at the effects of chemical modification of the methyl eugenol molecule to determine if 1) the molecule was as attractive as the parent (methyl eugenol) and 2) whether or not we could use the unique metabolic detoxification pathways of the insect to design a molecule that was both attractive and toxic specifically to the fly. Our results showed that although attraction could be maintain in some of the modified molecules, toxicity was not sufficient to achieve the desired results. Still we believe that understanding how pest insects behave to attractants and their metabolism of the compounds they feed on may yet allow us to develop better control products against this pest.
Technical Abstract: Oriental fruit fly, Bactrocera dorsalis (Hendel), males are highly 1 attracted to the natural phenylpropanoid methyl eugenol (ME). They compulsively feed on ME and metabolize it to ring and side-chain hydroxylated compounds that have both pheromonal and allomonal properties. Previously, we demonstrated that mono-fluorination at the terminal carbon of the ME side-chain significantly reduced metabolic side-chain hydroxylation while mono-fluorination of ME at position 4 of the aromatic ring blocks ring-hydroxylation but surprisingly enhanced side chain hydroxylation. In the current paper, we demonstrate that the introduction of fluorine atoms on both the ring and side-chain of ME blocks both positions which undergo enzymatic hydroxylation, and in particular completely inhibits oxidative biotransformation of the allyl group. In laboratory experiments, oriental fruit fly males were initially more attracted to both 1- fluoro-4,5-dimethoxy-2-(3,3-difluoro-2-propenyl)benzene (I) and 1-fluoro-4,5-dimethoxy-2-(3- fluoro-2-propenyl)benzene (II) than to ME. However, both I and II were consumed at rates significantly less than ME. Flies fed with difluoroanalog II partially metabolize it to 5-fluoro-4- (3-fluoroprop-2-en-1-yl)-2-methoxyphenol (III), and flies fed with trifluoroanalog I produce 4- (3,3-difluoroprop-2-en-1-yl)-5-fluoro-2-methoxyphenol (V) but the rates of metabolism relative to intakes were much lower compared to ME. Flies that consumed either the tri- or difluorinated analog showed higher post-feeding morality than those fed on methyl eugenol. In field trials, 18 trifluoroanalog I was ~90% less attractive to male B. dorsalis than ME, while difluoroanalog II was ~50% less attractive. These results suggest that although increasing fluorination can contribute to fly mortality, the trade off with attractancy makes it unlikely that either a di or trifluorinated ME would be an improvement in current use of ME for detection and/or eradication of this species.