Di- and Tri-fluorinated Analogs of Methyl Eugenol: Attraction to and Metabolism in the Oriental Fruit Fly, Bactrocera Dorsalis (Hendel)

Abstract

Oriental fruit fly, Bactrocera dorsalis (Hendel), males are attracted to the natural phenylpropanoid methyl eugenol (ME). They feed compulsively 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 blocked ring-hydroxylation but surprisingly enhanced side-chain hydroxylation. Here, we demonstrated that the introduction of fluorine atoms on both the ring and side-chain of ME blocks both positions that undergo enzymatic hydroxylation and, in particular, completely inhibits oxidative biotransformation of the allyl group. In laboratory experiments, B. dorsalis males initially were 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 taken up by flies at rates significantly less than that of ME. Flies fed with difluoroanalog II partially metabolized it to 5-fluoro-4-(3-fluoroprop-2-en-1-yl)-2-methoxyphenol (III), and flies fed with trifluoroanalog I produced 4-(3,3-difluoroprop-2-en-1-yl)-5-fluoro-2-methoxyphenol (V), but the rates of metabolism relative to rates of intakes were much lower compared to those of ME. Flies that consumed either the tri- or difluorinated analog showed higher post-feeding mortality than those that fed on methyl eugenol. In field trials, trifluoroanalog I was ∼90% less attractive to male B. dorsalis than ME, while difluoroanalog II was ∼50% less attractive. These results suggest that increasing fluorination can contribute to fly mortality, but the trade off with attractancy makes it unlikely that either a di or trifluorinated ME would be an improvement over ME for detection and/or eradication of this species.

BdorOR88a Modulates the Responsiveness to Methyl Eugenol in Mature Males of Bactrocera dorsalis (Hendel)

“…Particularly noteworthy is the fact that ME has its risks, however: it is carcinogenic to humans and its attractiveness is limited to mature males ( Smith et al, 2002 ; Khrimian et al, 2009 ; Zheng et al, 2012 ). Although novel attractants of B. dorsalis are diligently being developed, their progress toward better and more affordable attractants has nonetheless been slow ( Khrimian et al, 1994 , 2006 , 2009 ; Jang et al, 2011 ). Design of attractants to target specific ORs may promote the development of new baits for pest management ( Di et al, 2017 ; Mitchell et al, 2017 ).…”

BdorOBP2 plays an indispensable role in the perception of methyl eugenol by mature males of Bactrocera dorsalis (Hendel)

“…In addition, ME can trap sexually mature male flies, but it fails to attract immature males or females. Although, several analogues of ME have been developed 13 , 15 – 17 , the trade-off with male attractancy makes them an unlikely improvement over ME for detecting the oriental fruit fly in the field. Therefore, clarifying the molecular mechanism underlying the olfactory perception of ME should provide much-needed information for the developing of efficient, simple, green and sustainable lures for monitoring and controlling B. dorsalis pest populations.…”

Responses of fruit flies (Tephritidae:Dacinae) to novel male attractants in northQueensland,Australia, and improved lures for some pest species

“…, ; Jang et al . , ). However, any lures tested where there is a limited number of invasive species will only provide information on how those particular species respond to those compounds but not on potential responses of other species.…”