PHA-Exchange> Cinnamon Oil Found Effective In Mosquito Control

[claudio at hcmc.netnam.vn]

[The Journall of Agricultural and Food Chemistry article itself can be
accessed directly at:
    http://pubs.acs.org/cgi-
bin/abstract.cgi/jafcau/2004/52/i14/pdf/jf0497152.pdf]
Cinnamon oil kills mosquitoes

Cinnamon oil shows promise as a great-smelling, environmentally friendly
pesticide, with the ability to kill mosquito larvae, according to a new
study published in the July 14 issue of the Journal of Agricultural and
Food Chemistry, a peer-reviewed journal of the American Chemical Society,
the worldUs largest scientific society.

The researchers also expect that cinnamon oil could be a good mosquito
repellant, though they have not yet tested it against adult mosquitoes.

Besides being a summer nuisance, mosquitoes pose some major public health
problems, carrying such deadly agents as malaria, yellow fever and West
Nile virus. While conventional pesticide application is often effective in
controlling mosquito larvae before they hatch, repeated use of these
agents has raised serious environmental and health concerns.

"These problems have highlighted the need for new strategies for mosquito
larval control," says Peter Shang-Tzen Chang, a professor in the School of
Forestry and Resource Conservation at National Taiwan University and lead
author of the paper. Scientists are increasingly turning to more benign
natural chemicals to ward off mosquitoes and other pests.

Chang and his coworkers 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 cinnamonUs potential as a safe and effective pesticide,
according to Chang.

Cinnamaldehyde is the main constituent in cinnamon leaf oil and is used
worldwide as a food additive and flavoring agent. 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 TaiwanUs 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 havenUt yet tested this
theory, but they plan to find out in the near future.

The Council of Agriculture of the Executive Yuan, a government agency in
Taiwan, provided support for this research.



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