A New Use for a Feline Favorite

The arrival of spring-like weather is a sure sign that summer - and mosquito season - is just around the corner.  To help combat the onslaught of mosquitoes and other biting insects, you can choose from several commercially available synthetic or "natural" insect repellents.  While N,N-diethyl-3-methylbenzamide (CAS Registry Number® 134-62-3), commonly known as DEET, is viewed as "the standard by which all other repellents are judged",1 the next big thing in insect control may come from a plant better known for its effect on cats.

According to a recent study of the essential oil from the catmint plant (Nepeta cataria):

  • "Overall, the data indicates this material is a highly effective insect repellent against some of the key nuisance and disease vector species of biting insects."2

The idea of using the catmint plant, or catnip, to control insects isn't exactly new.  Nepetalactone (CAS Registry Number 490-10-8), the substance known to elicit odd behavior in cats, was identified in the essential oil of the catmint plant in 1941.3  A report by entomologist Thomas Eisner in 1964 described a possible reason the catmint plant produces nepetalactone, because "surely, a mint plant derives no benefit from an ability to stimulate cats!".4  In fact, his findings suggest that the purpose of nepetalactone is to repel plant-eating insects, a function shared by similar cyclopentanoid monoterpenes identified in other plants.  Eisner concluded:

  • "There is always the possibility that secondary plant substances might be of potential practical use as insect repellents... one would think that the cyclopentanoid monoterpenes might themselves be investigated profitably with this end in mind."4

Forty-five years later, it appears that Eisner's idea of a catmint-based insect repellent may soon reach the U.S. market.  Researchers at Iowa State University were granted a U.S. patent in 2003 for a nepetalactone-based insect repellent,5 followed in 2004 by a similar U.S. patent application filed by DuPont.6  Importantly, the active ingredient in DuPont's invention, Refined Oil of Nepeta cataria, has also been registered by the U.S. Environmental Protection Agency.  According to a recent press release:

  • "DuPont has received registration from the U.S. Environmental Protection Agency (EPA) for an insect repellent ingredient derived from the catmint plant, a sustainable resource more commonly known and loved by felines worldwide as catnip."7

You can use SciFinder® or STN® to search the CAS databases for additional information about Nepeta cataria, nepetalactone, and DEET.  If your organization is enabled to use the web version of SciFinder, you can click the links in this article to directly access details of the substances and references.

Contributed by
Peter S. Carlton, Ph.D.
CAS Communications


References
  1. American Mosquito Control Association (AMCA). http://www.mosquito.org/ (accessed May 8, 2009).
  2. Spero, N.C.; Gonzalez, Y.I.; Scialdone, M.A.; Hallahan, D.L. Repellency of Hydrogenated Catmint Oil Formulations to Black Flies and Mosquitoes in the Field. J. Med. Entomol. 2008, 45, 1080-1086.
  3. McElvain, S.M.; Bright, R.D.; Johnson, P.R. The Constituents of the Volatile Oil of Catnip. I. Nepetalic Acid, Nepetalactone and Related Compounds. J. Am. Chem. Soc. 1941, 63, 1558-1563.
  4. Eisner, T. Catnip: Its Raison d'Etre. Science 1964, 146, 1318-1320.
  5. Coats, J.R.; Peterson, C.J.; Zhu, J.; Baker, T.C.; Nemetz, L.T. Biorational Repellents Obtained from Terpenoids for use Against Arthropods. U.S. Patent 6,524,605, Feb 25, 2003.
  6. Hallahan, D.L. Preparation of Dihydronepetalactone as Insect Repellent. U.S. Patent Application 20040127553, July 1, 2004.
  7. DuPont. http://www2.dupont.com/DuPont_Home/en_US/index.html (accessed May 8, 2009).

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