In their quest for new insect repellents, researchers at the University of Guelph and the University of Mississippi have found that folk remedies provided good leads. They have identified the compounds in sweetgrass that repel mosquitoes.
Lead researcher Charles Cantrell said, "Sweetgrass gave off a sweet aroma that repels mosquitoes." The research team performed steam distillation on sweetgrass samples and evaluated its oil for the ability to deter mosquitoes from biting. The team filled small vials with a red-colored feeding solution that mimicked human blood and covered the vials with a thin membrane. The researchers coated the membranes with different substances i.e. the sweetgrass oil, alternative sweetgrass extracts obtained without steam distillation, the gold-standard insect repellent.
They observed what the insects did by counting how many mosquitoes went for a bite of each type of 'blood' vat. Further, the researchers purified the oil into 12 fractions and again checked their ability to ward off the mosquitoes. They found three fractions that repelled mosquitoes as well as the oil. Using nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry, the research team identified two chemicals in these active fractions that seemed to be responsible for putting off mosquitoes, which were phytol and coumarin.