Location: Mosquito and Fly ResearchTitle: Discovery of Repellents from Natural Products Author
|Tabanca, Nurhayat - University Of Florida|
|Bernier, Ulrich - Uli|
|Agramonte, Natasha - University Of Florida|
|Tsikolia, Maia - University Of Florida|
|Bloomquist, Jeffrey - Mississippi State University|
Submitted to: Current Organic Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2016
Publication Date: 10/20/2016
Citation: Tabanca, N., Bernier, U.R., Agramonte, N., Tsikolia, M., Bloomquist, J.R. 2016. Discovery of Repellents from Natural Products. Current Organic Chemistry. DOI: 10.2174/1385272820666160421151503.
Interpretive Summary: Scientists at the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology, University of Florida, University of Mississippi, and Turkey collaborated to report the results of repellents tests of natural products extracted from plants. Extracts and compounds were tested for as repellents against the Yellow fever mosquitoes (Aedes aegypti). Based on the results of the study, a chemical called carvacrol is the strongest repellent. Unfortunately, this compound feels uncomfortable when put on the skin. This paper also describes how to extract chemicals for repellent testing and how certain chemical structures are better repellents. The results of this study benefit people at risk of mosquito attack throughout the world, and may be of specific use to researchers and commercial entities that are developing new repellents for personal protection from mosquito attack.
Technical Abstract: Natural products are an ideal source of chemicals for topical application to human skin, and can be a means of personal protection from the bites of mosquitoes and other arthropods. This report covers a diverse array of natural compounds, and includes descriptions of observed correlations between chemical properties and repellency. Repellent efficacy is determined by a ‘cloth-patch’ assay, which involves human volunteers testing chemically-treated cloth in cages of adult female mosquitoes. Known concentrations of chemical are applied to cloth and the treated cloth is affixed on the arm of a volunteer. The volunteer inserts the clothed arm into a cage of adult female mosquitoes to determine if they will land and bite through the treated cloth. The Minimum Effective Dosage (MED) is determined as the threshold concentration at which 1% of the mosquitoes bite through the treated cloth. This standardized assay has been used to develop in silico models to predict the relationship between chemical and structural properties, as well as the repellent performance. This report covers the past several years of our research, which has focused on natural products and essential oils extracted from plant species from different parts of the world. Structural indicators, such as the location of an oxygen or double bond in small molecules, have been found to predict repellency. The most potent natural repellent in our studies is carvacrol; however, this compound is also a skin irritant. Thymol, as well as a-terpineol, eugenol, and carvacrol methyl ether were also highly efficacious against Aedes aegypti. This work may lead to the discovery of derivatives of these compounds which possess both repellent efficacy and dermal safety.