Next-gen insect repellents to combat mosquito-borne diseases

phys.org | 8/20/2018 | Staff
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Nearly 700 million people suffer from mosquito-borne diseases—such as malaria, West Nile, Zika and dengue fever—each year, resulting in more than 1 million deaths. Increasingly, many species of mosquitoes have become resistant to the popular pyrethroid-based insecticides. Today, researchers report a new class of mosquito repellents based on naturally occurring compounds that are effective in repelling mosquitoes with potentially fewer environmental side effects than existing repellents.

The scientists will present their research today at the 256th National Meeting & Exposition of the American Chemical Society (ACS).

Repellents - Joel - R - Coats - PhD

"Our new repellents are based on how nature already works," Joel R. Coats, Ph.D., says. "For example, citronella, a spatial repellent that comes from lemongrass, contains naturally occurring essential oils that have been used for centuries to repel mosquitoes. But citronella doesn't last long and blows away easily. Our new, next-generation spatial repellents are variations of natural products that are longer-lasting and have greater repellency."

Coats and graduate students James S. Klimavicz and Caleb L. Corona at Iowa State University in Ames have been synthesizing and testing hundreds of compounds against mosquitoes. They knew that sesquiterpenoids, which are found in many plants, are effective insect repellents, but these large molecules are difficult to isolate from plants and hard to make and purify in the laboratory.

Challenges - Sesquiterpenoids - Coats - Team - Repellents

Because of the challenges of synthesizing sesquiterpenoids, Coats' team designed their repellents using smaller, less complex, easily obtainable molecules—monoterpenoids and phenylpropanoid alcohols with known, short-term repellent activities against insects. By modifying these compounds chemically, they produced new potential repellents with higher molecular weights, making them less volatile and longer-lasting. Klimavicz has synthesized more than 300 compounds, the most effective of which are α-terpinyl isovalerate (a natural compound), citronellyl cyclobutanecarboxylate and citronellyl 3,3-difluorocyclobutanecarboxylate.

To determine the compounds' effectiveness as repellents against mosquitoes, Corona tests them in a tubular chamber developed in the Coats laboratory. The...
(Excerpt) Read more at: phys.org
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