|ALI, ABBAS - University Of Mississippi|
|ALI, ZULFIQAR - University Of Mississippi|
|KHAN, IKHLAS - University Of Mississippi|
Submitted to: International Journal of Current Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/13/2019
Publication Date: 9/30/2019
Citation: Ali, A., Li, A.Y., Tabanca, N., Ali, Z., Khan, I.A. 2019. Insecticidal and repellent activities of cinnamates against mosquitoes and ticks. International Journal of Current Research. 11(09):6814-6818.
Interpretive Summary: Mosquitoes and ticks are important vectors of human diseases, such as malaria, Zika, West Nile, and Lyme disease, that impact global public health. Synthetic pesticides have been used widely for vector control and vector-borne disease prevention. Use of insect repellents, such as DEET, can prevent infected mosquitoes or ticks from biting humans, therefore reduce the risk of vector-borne diseases. Due to public concerns over the safety of the common repellent DEET, researchers are searching for effective and safe naturally derived compounds as alternative to DEET against blood sucking disease vectors. In collaboration with university researchers, USDA-ARS scientists conducted a study to evaluate the toxicity and repellency of two new natural compounds against mosquitoes and ticks through laboratory bioassays. One of the compounds was found to have a high residual repellency against mosquitoes; therefore, can potentially be developed as a mosquito repellent. The results obtained from this study are of interest to researchers and pest control professionals who work in the field of repellent development and vector control.
Technical Abstract: Three natural flavor and fragrance compounds, n-butyl cinnamate, benzyl cinnamate, and benzyl cinnamate, were evaluated for toxicity and repellency against mosquitoes and ticks in this study. n-Butyl cinnamate showed the highest level of toxicity among the tested cinnamates with LC50 value of 7 ppm followed by benzyl cinnamate (LC50= 8.4 ppm) and phenethyl cinnamate (LC50= 10.3 ppm) against 1-d old Ae. aegypti larvae. In Klun & Debboun (K&D) biting deterrence bioassay, these three compounds showed biting deterrent activity above the solvent control. n-Butyl cinnamate and benzyl cinnamate with proportion not biting (PNB) values of 0.8 and 0.74, respectively, were similar to DEET while the activity of phenethyl cinnamate was lower than DEET and the other compounds at a rate of 25 nmol/cm2. In Ali and Khan (A&K) bioassay, n-butyl cinnamate was active at the lowest dose of 5.9 µg/cm2 followed by DEET and benzyl cinnamate that were active at 11.7 µg/cm2 whereas phenethyl cinnamate did not show repellent activity at the highest dose of 93.7 µg/cm2. Based on repellency data, n-butyl cinnamate was tested for residual repellency. Both DEET and n-butyl cinnamate were within the limits of the minimum effective dose (MED) up to 120 min at a dose of 23 .4 µg/cm2. At 11.7 µg/cm2, DEET crossed MED threshold after 30 min whereas n-butyl cinnamate was active up to 120 min. In tick bioassays, the repellent activity of n-butyl cinnamate at the concentration of 2.5% was similar to DEET at 1.25% n-butyl cinnamate demonstrated reasonably good concentration-repellency response. In contrast, benzyl cinnamate did not demonstrate significantly repellency when compared to DEET at the highest dose of 5%. High residual repellency of n-butyl cinnamate indicated its potential to be used as mosquito repellent.