First identification of four new limonoids that deter leaf-eating pests
Washington, D.C. - Naturally occurring substances that appear to repel a leaf-eating insect pest have been found in the leaves of Spanish cedar trees, according to results of a study by British researchers published in the Sept. 24 issue of the Journal of Natural Products, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society.
The researchers, based at the Royal Botanic Gardens, Kew, the University of Oxford, and the Natural Resources Institute at the University of Greenwich, say that selecting seedlings with high concentrations of these previously unidentified substances, known as limonoids, may help in the production of plantation-raised Spanish cedars while also reducing the need for synthetic insecticides.
Spanish cedars are hardwood members of the mahogany sub-family and have great economic importance worldwide for their use in buildings and in furniture. Trees such as Spanish cedars are mostly harvested from the wild, but with growing demand for their timber, the need for plantations is increasing. However, the success of plantation-raised trees is seriously constrained by damage from insects such as mahogany webworms and shoot-borers, as well as the insect examined in this study, a weevil known as Exopthalus jekelianus. If plantation-raised timber production does not succeed already endangered primary forests are threatened even further, the scientists note.
"The four compounds we identified are new to science," said Philip C. Stevenson, Ph.D., natural product chemist at the Jodrell Laboratory of the Royal Botanic Gardens and the Natural Resources Institute at the University of Greenwich, and the study's primary coordinator. "As well, our study was the first to examine Spanish cedar leaves for the particular group of substances (known as triterpenoids, which include limonoids) in tandem with the first extensive field observations of insect feeding patterns on Spanish cedars. We are providing field observations rather than mere in vitro (laboratory) evidence that insects actually reject leaves containing these substances. We hope our findings will help in the protection of endangered primary forests in the tropics by promoting economically viable alternatives for timber production."
Stevenson and his colleagues, Nigel G. Veitch, also of the Royal Botanic Gardens, Geraldine A. Wright, now at Ohio State University but formerly at the University of Oxford, and Steve Simpson, of the University of Oxford, have other work in progress that describes the behavior of Exopthalus jekelianus in more detail.
A nonprofit organization with a membership of nearly 159,000 chemists and chemical engineers, the American Chemical Society publishes scientific journals and databases, convenes major research conferences, and provides educational, science policy, and career programs in chemistry. Its main offices are in Washington, D.C., and Columbus, Ohio. ( http://www.acs.org )
Journal
Journal of Natural Products