Citrus Oils May Hold Key to Asthma Prevention

Newswise — A key to preventing asthma might be found in a lemon, a rose or a pine tree. According to a study at the Technion-Israel Institute of Technology, inhalation of limonene, the main component found in the essential oil of citrus, prevented asthma symptoms in animals. The findings are published in this week's Bioorganic and Medicinal Chemistry.

Inspired by previous findings that show the incidence of asthma to be five times higher in urban areas than in rural and agricultural ones, lead researcher Professor Ehud Keinan studied the connection between ozone and asthma and other lung disorders. He believes this higher incidence of asthma is due in large part to the absence of natural "ozone scavengers" produced by plants.

"Ozone in the outer atmosphere is essential for life on earth because it absorbs the destructive ultraviolet radiation emitted by the sun," he explained. "But on earth, it is a dangerous component of air pollution. Numerous studies have shown exposure to ozone, even at low levels, induces airway inflammation and lung injury in humans and animals."

Keinan's team also found that ozone is produced in inflammatory tissues by antibodies as a defense against asthma. The presence of this ozone activates more antibodies, perpetuating a vicious cycle.

The research team says that "ozone-scavengers" " substances that devour ozone " could be used for preventing asthma. The inhalation of water-repellent ozone scavengers that accumulate in lung membranes could break the cycle of inflammation. Organic compounds called monoterpenes -- produced by all plants -- are ideal sources of such substances.

Limonene, an unsaturated monoterpene and the main component in the essential oil of citrus, functions extremely well as an ozone scavenger. Other ozone scavenging monoterpenes studied by the team came from roses, pine trees and citronella, but limonene was the most effective. Saturated monoterpenes, however -- such as those found in eucalyptol -- were found to have no ozone scavenging properties.

The experiments involved exposing rats with induced asthma-like symptoms to either limonene or eucalyptol for a couple of days. The lung function of the rats showed that limonene inhalation prevented the asthmatic symptoms. The anti-inflammatory effect of limonene was also supported by pathological evidence.According to the American Lung Association Epidemiology & Statistics Unit Research and Scientific Affairs, more than 20 million Americans (6.1 million of them children) suffered from asthma in 2002.

The research included Technion graduate student Aaron Alt, Dr. David Shoseyov of the Hadassah Mount Scopus University hospital, Dr. Haim Bibi of the Barzilai Medical Center, Ashkelon, Dr. Gail Amir of the Hadassah University hospital and Dr. Lea Bentur of the Technion Medical Faculty.

The Technion-Israel Institute of Technology is Israel's leading science and technology university. Home to the country's only winners of the Nobel Prize in science, it commands a worldwide reputation for its pioneering work in computer science, biotechnology, water-resource management, materials engineering, aerospace and medicine. The majority of the founders and managers of Israel's high-tech companies are alumni. Based in New York City, the American Technion Society is the leading American organization supporting higher education in Israel, with more than 20,000 supporters and 17 offices around the country.