Going Camping? Pack a Tomato
By Hannah Hoag
Next summer, campers and picnickers may be turning to a tomato extract to keep the mosquitoes from biting.
Michael Roe, an entomologist at North Carolina State University, was designing synthetic insecticides when he realized their structures resembled that of an oily organic compound that occurs naturally in tomatoes. "I thought I would test the substance as an insect repellent--on a whim, basically," he says. Roe grabbed a cloth, dabbed it with a synthetic version of the tomato molecule, and placed it in a cage full of cockroaches. They scattered. He then did additional tests to show that the molecule repelled mosquitoes and ticks as well.
Alan Brandt, president and chief operating officer of Insect Biotechnology Inc., a Durham, North Carolina, company that develops and markets insecticides, caught wind of this discovery while he was working with Roe on several other projects. He decided to compare the tomato compound to DEET, the most popular and effective commercial bug repellent. Each year approximately one-third of Americans spray or spread DEET-based insect repellents on their skin to keep bugs at bay.
A 20 percent solution of the tomato extract, applied to the arms of volunteers, repelled mosquitoes as effectively as the same concentration of DEET. But during a 12-hour test, DEET's efficacy slipped, letting 4 out of every 100 mosquitoes take a nibble. Arms covered with the tomato-derived compound stayed bite-free. DEET also has been linked to adverse reactions, including irritated skin, rashes, and blisters. The Environmental Protection Agency considers DEET to be safe when used correctly, but many parents worry about exposing their children to the chemical. "People are looking for an alternative," says Brandt.
For proprietary reasons, Insect Biotechnology will not reveal the name of the insect-repelling molecule. The company calls it IBI-246; IBI stands for the company's name. Brandt says that while the compound is well known and used in other products, he will not identify it until after a patent for its use as a repellent has been granted. Even to those in the know, IBI-246 is somewhat mysterious: Neither Roe nor Brandt understands exactly how it deters mosquitoes from their blood quest. Brandt suspects that, like DEET, the compound disrupts a chemical receptor on the mosquito's antennae that the insect uses to guide itself to its prey. Tomatoes probably create this molecule as part of the plant's natural anti-insect arsenal, Roe says.
Because the tomato-derived substance is a naturally occurring compound that is already used in other products, including cosmetics, it is known to be safe and unlikely to produce any adverse skin reactions. Brandt expects to have the tomato-inspired bug repellent on the market by the time the mosquitoes start biting in 2003.