Although previous studies by the researchers showed that salsa has antibacterial activity, this new study represents the first time that they have isolated any of the antibacterial compounds from it. Their study appears in the May 26 issue of the Journal of Agricultural and Food Chemistry, a peer-reviewed publication of the American Chemical Society, the world's largest scientific society.
The compound — dodecenal — was isolated from the fresh leaves of cilantro, or coriander, one of the main ingredients found in salsa, along with tomatoes, onions and green chilies. The compound also is found in the seeds of cilantro. Both leaves and seeds contain about the same amount of dodecenal, but the leaves are used more abundantly in salsa.
In laboratory tests, dodecenal was twice as potent as the commonly used medicinal antibiotic gentamicin at killing Salmonella, a frequent and sometimes deadly cause of foodborne illness, the researchers say. It is the only naturally occurring antibacterial that is more effective than gentamicin against Salmonella, they claim.
"We were surprised that dodecenal was such a potent antibiotic," says study leader Isao Kubo, Ph.D., a chemist with the University of California, Berkeley. Most natural antibacterial agents found in food generally have weak activity.
"The study suggests that people should eat more salsa with their food, especially fresh salsa," Kubo adds.
In addition to dodecenal, about a dozen other antibiotic compounds were isolated from fresh cilantro that show some activity against a variety of harmful bacteria. Salsa likely contains even more antibacterial compounds that have not yet been identified, according to Kubo.
The findings could lead to expanded use of dodecenal as a tasteless food additive to prevent foodborne illness, perhaps as a protective coating for meats in processing plants, or even as a general purpose disinfectant to be used in cleaning and hand washing, Kubo says.
But don't rely on salsa alone to safeguard your food: There's only a small amount of the potent antibacterial in a typical serving. "If you were eating a hot dog or hamburger," explains Kubo, "you would probably have to eat an equivalent weight of cilantro to have an optimal effect against food poisoning."
The researchers say that their lab does not plan to market dodecenal as a bacteria fighter or test it further to see if it works in humans. But they acknowledge that their findings are attractive for industry and others wanting to develop better ways to combat foodborne illness.
Dodecenal also shows promise in side-stepping the growing problem of antibiotic resistance. The researchers believe the compound works by destroying the cell membrane of bacteria, similar to the way soap kills bacteria. As the compound does not appear to interfere with any of the protein-manufacturing machinery of the cell, as occurs with many commercial antibiotics, bacteria are less likely to develop resistance to it, Kubo says.
Whether you choose to eat salsa with your tacos, chips or chicken, keep in mind that there's no substitute for proper storage, handling and cooking of any food in order to prevent foodborne illness, according to health experts.
The University of California, Berkeley, and the University of California Institute for Mexico and the United States (UC MEXUS) provided funding for this study.
Kubo's associates in this study were Ken-ichi Fujita, Aya Kubo and Ken-ichi Nihei, of UC Berkeley, and Tetsuya Ogura, of Universidad Autonoma de Guadalajara, Mexico.
— Mark T. Sampson
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