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Smelling Citrus Oils Prevents Asthma in Rats
By Alison McCook
NEW YORK
(Reuters Health) -
A key
ingredient in the aroma from citrus fruits such as oranges and lemons
appears to protect rats from the symptoms of asthma, new research
shows.
Study author Dr. Ehud Keinan explained that the citrus ingredient
is called limonene, and it likely protects against asthma by "burning"
inhaled ozone, which can increase inflammation in the lungs.
Other scents - such as those emitted from pine trees, geraniums
and roses - contain similar ingredients to limonene, Keinan said,
which may help explain why asthma is much more common in urban areas
that lack vegetation.
"In rural populations, people are very much exposed to these
compounds," he said.
The researcher, who is based at the Technion-Israel Institute of
Technology in
Israel,
told Reuters Health that squeezing an orange peel releases liquid that
contains a high concentration of limonene. He said he has heard
stories of people who say they experienced relief from asthma and
other lung diseases after spending time around limonene.
He added that he and his colleagues, who report their current
findings in the journal Bioorganic & Medicinal Chemistry, are
currently investigating how limonene and similar substances may help
alleviate asthma in humans.
A growing body of research suggests that ozone, which is a key
component of air pollution, can encourage changes in the body that
result in persistent inflammation in the airways.
Limonene helps rid the body of ozone because it reacts with
ozone, muting its toxic effects, Keinan explained.
To investigate whether limonene could protect lungs from asthma,
Keinan and his team induced the symptoms of asthma in rats, them let
them smell limonene or eucalyptol, the key ingredient in the odor of
eucalyptus, which does not react with ozone.
The researchers checked the rats for asthma symptoms repeatedly
over a period of 20 hours to five days. They found that only rats
exposed to limonene "didn't show any symptoms of the disease," Keinan
said.
These results suggest that inhaling limonene may protect people
from developing asthma, or alleviate symptoms in those already
diagnosed, he noted.
SOURCE: Bioorganic & Medicinal Chemistry,
December 8, 2004.
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