Location: Mosquito and Fly ResearchTitle: Insecticidal, repellent and fungicidal properties of novel trifluoromethylphenyl amides) Author
|Bernier, Ulrich - Uli|
|Linthicum, Kenneth - Ken|
Submitted to: Pesticide Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2013
Publication Date: 6/18/2013
Citation: Tsikolia, M., Bernier, U.R., Coy, M.R., Chalaire, K.C., Becnel, J.J., Agramonte, N.M., Tabanca, N., Wedge, D.E., Clark, G.G., Linthicum, K., Swale, D.R., Bloomquist, J.R. 2013. Insecticidal, repellent and fungicidal properties of novel trifluoromethylphenyl amides. Pesticide Biochemistry and Physiology. 107:138-147. Interpretive Summary: Scientists at the USDA-ARS, Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, FL, synthesized 20 trifluoromethylphenyl amides, of which 13 were novel. All compounds were evaluated for insecticidal, repellent, and fungicidal activity. One amide was 2.3 times more repellent against female Aedes aegypti than the standard repellent N,N-diethyl-3-methylbenzamide (DEET). A second amide had repellency comparable to DEET while a third compound exhibited some ability to control Phomopsis species. Although none of the novel amides were extremely potent insecticides against mosquitoes, a few may serve as the basis for the design of additional, novel insecticides.
Technical Abstract: Twenty trifluoromethylphenyl amides were synthesized and evaluated as fungicides and as mosquito toxicants and repellents. Against Aedes aegypti larvae, (trifluoromethyl)phenyl)-3,5-dinitrobenzamide (1e) was the most toxic compound (24 h LC50 1940 nM), while against adults (trifluoromethyl)phenyl)-2,2,2-trifluoroacetamide (1c) was most active (24 h LD50 19.182 nM, 0.5 'l/insect). However, the 24 h LC50 and LD50 values of fipronil against Ae. aegypti larvae and adults were significantly lower: 13.55 nM and 0.787 10-4 nM, respectively. Compound 1c was also active against Drosophila melanogaster adults with 24 h LC50 values of 5.6 and 4.9 'g/cm2 for the Oregon-R and 1675 strains, respectively, compared to fipronil. Fipronil had LC50 values of 0.004 and 0.017 'g/cm2 gainst the two strains of D. melanogaster, respectively. In repellency bioassays against female Ae. aegypti, 2,2,2-trifluoro-N-(2-(trifluoromethyl)phenyl)acetamide (4c) had the highest repellent potency with a minimum effective dosage (MED) of 0.039 'mol/cm2 compared to DEET (MED of 0.091'mol/cm2). The compound N-(2-(trifluoromethyl)phenyl)hexanamide (4a) had a MED of 0.091'mol/cm2 which was comparable to DEET. Compound 4c was the most potent fungicide against Phomopsis obscurans. Several trends were discerned between the structural configuration of these molecules and the effect of structural changes on toxicity and repellency. Para- or meta- trifluoromethylphenyl amides with an aromatic ring attached to the carbonyl carbon showed higher toxicity against Ae. aegypti larvae, than ortho- trifluoromethylphenyl amides. Ortho- trifluoromethylphenyl amides with trifluoromethyl or alkyl group attached to the carbonyl carbon produced higher repellent activity against female Ae. aegypti and Anopheles albimanus than meta- or para- trifluoromethylphenyl amides. The presence of 2,6-dichloro- substitution on the phenyl ring of amide had influence on larvicidal and repellent activity of para- trifluoromethylphenyl amides.