Cinnamon oil may be an environmentally friendly pesticide, with the ability to kill mosquito larvae

A new study published in the Journal of Agricultural and Food Chemistry, shows that cinnamon oil may be an environmentally friendly pesticide, with the ability to kill mosquito larvae.

Researchers from the National Taiwan University also suggest that cinnamon oil could be used as a mosquito repellant.

Peter Shang-Tzen Chang, a professor in the School of Forestry and Resource Conservation at the National Taiwan University tested eleven compounds in cinnamon leaf oil for their ability to kill emerging larvae of the yellow fever mosquito, Aedes aegypti.

"Four compounds — cinnamaldehyde, cinnamyl acetate, eugenol and anethole — exhibited the strongest activity against A. aegypti in 24 hours of testing," Chang says.

Larvicidal activity is judged with a measurement called LC50. "The LC50 value is the concentration that kills 50 percent of mosquito larvae in 24 hours," Chang explains. Lower LC50 translates into higher activity, because it takes a lower concentration to kill larvae in the same amount of time. All four compounds had LC50 values of less than 50 parts per million (ppm), with cinnamaldehyde showing the strongest activity at an LC50 of 29 ppm.

Other common essential oils, such as catnip, have shown similar promise in fighting off mosquitoes, but this is the first time researchers have demonstrated cinnamon’s potential as a safe and effective pesticide, according to Chang.

Cinnamaldehyde (cinnamic aldehyde) is the main component in cinnamon bark oil and is used in flavoring compounds to impart a cinnamon flavor. Considerable safety data exist from the food and flavoring industry which utilizes food grade cinnamaldehyde in non-alcoholic beverages, ice cream, candy, baked goods, chewing gum, condiments and meats at levels ranging from 9 ppm to 4900 ppm.

A formulation using the compound could be sprayed just like a pesticide, but without the potential for adverse health effects — plus the added bonus of a pleasant smell.

Bark oil from the Cinnamomum cassia tree is the most common source of cinnamaldehyde, but the tree used in this study — indigenous cinnamon, or Cinnamomum osmophloeum — has been of interest to researchers because the constituents of its leaf oil are similar to those of C. cassia bark oil. The leaves of C. osmophloeum, which grows in Taiwan’s natural hardwood forests, could be a more economical and sustainable source of cinnamon oil than isolating it from bark, Chang says.

Though the team only tested the oil against the yellow fever mosquito, cinnamon oil should prove similarly lethal to the larvae of other mosquito species, the researchers say. In further studies they plan to test cinnamon oil against other types of mosquitoes as well as different commercial pesticides.

"We think that cinnamon oil might also affect adult mosquitoes by acting as a repellant," Chang says. The researchers haven’t yet tested this theory, but they plan to find out in the near future.