Sweetgrass Oil Repels Mosquitoes as Well as Deet

The researchers say folk remedies are a rich source of possible new repellents.

Using sweetgrass to keep the mosquitos away is nothing new to Native Americans. The researchers observed what the insects did, counting how many mosquitoes went for a bite of each type of “blood” Value-Added Tax. The research was presented this week at a meeting of the American Chemical Society in Boston. They also compared it with other repellents, including DEET.

Charles Cantrell and his team at the U.S. Department of Agriculture, in collaboration with researchers at the University of Guelph and the University of Mississippi, put the plant’s oil to the test. Man versus mosquito has not been a war won easily, and conventional repellants and pesticides can prove problematic for anyone concerned about exposure to chemicals and potential toxins. The vial was then covered with a thin membrane and laced with either the sweetgrass oil, other extracts of sweetgrass obtained without steam distillation, the gold standard of insect repellants called N, N-diethyl-m-toluamide (DEET) or the solvent alcohol as the negative control.

Cantrell and his colleagues exposed the vials to mosquitoes and monitored the number of insects that would feed on the solution and those that would pass them by.

“Then you take the mosquitoes and squish them on some paper”, Cantrell said in the release.

Up next, the laboratory plans to investigate additional folk remedies for pests to see if any could be eventually used as part of a commercial insect repellent on USDA-approved organic products.

Wanting deeper into the precise chemical compounds that work to fend off the pests, they discovered three fractions of the oil that repelled mosquitoes in addition to the entire. Of all the options, the steam-distilled sweetgrass oil tested with the fewest mosquito bites, matching the repellent potency of DEET. The researchers purified the oil into 12 fractions and again checked their ability to ward off the bugs. They then made use of mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy to isolate two active chemicals that are responsible for repelling the mosquitoes.

Coumarin is an ingredient in some business anti-mosquito merchandise, he provides, whereas phytol is reported to have repelling exercise within the scientific literature.

“We’ve been able to show that [with] sweetgrass, there’s actually some scientific basis for what [Native Americans] were claiming the plant was used for, at least in the short term”, he said.