The smoke of breadfruit flowers has long been used as a traditional mosquito repellent in Oceania. A new study has verified its effectiveness and pointed to the compounds responsible.
By Tyler Irving
Posted May 2012
For centuries, Pacific islanders have burned breadfruit flowers to create a mosquito-repellent smoke. New research published in the Journal of Agricultural and Food Chemistry has identified the chemical substances responsible.
Max Jones led the research during his PhD in the Department of Biology at the University of British Columbia’s Kelowna campus. “During my literature review, I came across several mentions of burning the flowers to ward off flying insects, but no one had ever actually tested it before,” he says. Jones created extracts of both dried breadfruit flowers and smoke using a variety of solvents, as well as steam distillation. In collaboration with the U.S. Department of Agriculture, he tested those extracts using a bioassay involving boxes of hungry Aedes aegypti, the mosquito that carries yellow fever. The bugs were exposed to a feeding bag coated with the extracts or a control, and the extracts with the highest repellency were further fractioned and analysed using NMR and mass spectrometry. Eventually, the team identified capric acid, undecanoic acid and lauric acid as active compounds.
In the final experiment, the team found that commercially produced versions of these fatty acids, when applied in equimolar concentrations, performed even better than DEET (N,N-Diethyl-meta-toluamide), a common ingredient in mosquito repellents. In fact, previous large-scale screening studies have identified their potential as alternative mosquito repellents, and some companies are looking at using them in commercial repellent formulations. But for Jones, the most exciting part was validating the traditional use. “I was surprised to see how effective the compounds were; this wouldn’t be observed in just any smoke,” he says. “Breadfruit provides a food as well as mosquito repellent, in exactly the places that need these two items the most.”
Photo credit: Max Jones
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