Insect repellant from catnip

The U.S. Environmental Protection Agency recently registered a new insect repellent ingredient derived from the catmint plant, or "catnip" (flower, as pictured). The ingredient, Refined Oil of Nepeta cataria, is the first new insect repellent bio-pesticide to be registered in eight years. DuPont is the registrant.

CATNIP

DuPont's research demonstrates that the refined oil "repels a broad range of biting insects with effectiveness similar to synthetic ingredients such as DEET."

A key benefit is that consumers could apply it to skin as often as desired. Because it smells nice, it could be mixed into an existing product or formulated as straight repellent.

Although I never noticed whether being around wild catnip resulted in fewer mosquito bites, it sounded as if "biomimcry" was one of the principles driving Dupont's discovery. So, I contacted Henry Bryndza, Director of Chemical Sciences & Engineering, DuPont Central Research & Development. Find out what I learned, below.

John Laumer for TreeHugger: I know people will be wondering ‘If I use this product, will cats follow me home?’ Can you address this please?

Henry Bryndza for Dupont: We don’t believe it will be an issue but there are good options available if it is a concern. We’ve noticed no such behavior from cats in our field trials for the EPA. Catnip is actually a cat excitant, not an attractant, and interest falls off dramatically with distance.

We’ve also consulted with formulators who indicate that perfumers can incorporate cat repellents into formulations that use cat stimulants. One option is citronellol, another naturally derived product with mild insect repellent properties.

TH: I see that the development work was done in DuPont’s Crop Protection business. Have you contemplated using the extract to “repel” insects from crops; or is the catnip extract intended only for consumer products?

HB: We have not found any extraordinary efficacy in crop protection applications that would warrant development for that purpose. Our Refined Oil seems to have the greatest efficacy against biting insects such as mosquitoes, biting flies, etc. that bother people and pets more than plants.

TH: Would this product potentially qualify for organic registration?

HB: Our Refined Oil was registered through the bio-pesticide process with EPA and is based on a natural product. The crop and oil most likely could be certified ‘organic’.

TH: Will DuPont be commercially supplying catnip extracts to consumer product developers?

HB: We do have a limited supply of oil to supply to interested developers.

TH: Related question: when can we anticipate a commercial product containing catnip extract?

HB: We are actively working to find a development partner or licensee to help get this product to market. Timing to market will depend on that partner or licensee.

TH: Catnip is a semi-invasive non-native in the USA and there are numerous species. Did you have to select ones to work with; or is repellant efficacy more related to a DuPont technology?

HB: Through greenhouse studies we have selected a specific variety of the species Nepeta cataria that seems to be most efficacious for oil production. But the nepetalactone-containing oils from all of the species we have tested so far can be converted to an effective insect repellent using DuPont technology.

TH: Related question. Are the agricultural inputs for Nepeta relatively low or is intensive cultivation required?

HB: It seems to be quite a non-demanding plant that actually does best in somewhat harsh, arid environments. So agricultural inputs are relatively low, as many home gardeners can probably attest to.

TH: If the past is any guide we can expect a legion of knock off products that EPA will have to look into, as well as urban legends about smearing ones’ body with catnip leaves. Can you comment about the importance of governmental pesticide registrations, then, in preserving the value of DuPont’s intellectual property?

HB: First, thank you for the question – it’s important to stress that the major component in unrefined oil from Nepeta cateria is nepetalactone, which is a skin sensitizer; therefore, people should be actively discouraged from “smearing ones’ body” with catmint leaves. DuPont technology converts this major oil component into dihydronepetalactone, which is not a skin sensitizer and is much more stable and effective than the unprocessed oil.
We view the government regulations as prudent oversight designed to protect people rather than as a means of preserving intellectual property rights. We have many filed and issued patents, as well as the EPA registration, to protect our invention.

TH: It does seem as if this is one of those stories about something ‘hidden in plain sight’ for centuries, suddenly rediscovered. True?

HB: Not really. Without DuPont science and innovation, the natural product has significant limitations as an insect repellent, including the fact that the unrefined oil is a skin sensitizer and is not very stable.

TH: Would it be fair to say there is a “biomimicry” aspect to the discovery, or is this more a matter of serendipity?

HB: Certainly we depend on our scientists to look to nature and biomimicry, as well as other sources, for their inspiration. Nature has much to teach us and it’s important that we listen.

TH: In the early 1800s’ there had been a romantic and even a religious approach to botanical discovery making. The assumption was that for every disease God had provided a cure in nature and man only had to find it. Hence aspirin was discovered. Is that just a quaint notion, which should be disregarded; or has it been transformed into a new paradigm, for which this discovery is emblematic?

HB: I’ve never really thought about it that way. I do think nature has a lot to teach us. Nature evolved human beings and plants from the same amino acid building blocks so it is not at all inconceivable that things that are made in nature can be utilized successfully by the human body. Biomimcry is something we are paying a great deal of attention to here at DuPont.

The catmint project is one more example of humankind discovering a useful raw material in nature, and improving it to fit our needs. Examples include vulcanization of natural rubber, synthetic pyrethroid insecticides based on natural pyrethrum, and so on. TH: Related question. Does DuPont have to go bio-prospecting in distant lands for more such opportunities? Or are there likely to be more growing in our backyards?

HB: There’s a lot to be said for chance favoring the prepared mind. We look for leads everywhere; however, we do so with a distinct focus. The Crop Protection business focuses its research and development efforts on the discovery and development of sustainable new products that advance agriculture. We also strive to support and renew our existing product line in a way that continues to provide new and exciting answers to today’s pest control issues. The Refined Oil work sprang from this very focus.

HB: In the realm of bio-prospecting, DuPont is also developing biologically based materials and fuels that rely on nature. More information about these can be found at this link.

HB: DuPont also has a $35 million investment in an Alliance with Massachusetts Institute of Technology (MIT) where many of the scientists are working on early stage learnings from nature. Examples of research programs that have been part of this collaboration include:

1.Professor Mriganka Sur, head of the Brain and Cognitive Sciences Department: an early stage research program to develop a novel biopolymer-based nervous system implant that could replace nonfunctional brain tissue following traumatic brain injury; 

2.Professor Linda Griffith, director of the Biotechnology Process Engineering Center: a device for tissue-like culturing of liver cells, designed to provide early assessment of the toxicity of new pharmaceuticals;

3.Professor Michael Rubner, director of the Center for Material Science and Engineering: a novel material similar to the naturally water repellent surface of the lotus leaf. Potential applications include self-cleaning fabrics, water-repellant windshields, or plumbing that resists the growth of harmful bacteria by preventing water from accumulating on its surface.

TH: I’m sure I can speak for our readership when I say that conserving biodiversity seems a more practical goal in light of this announcement. Does it give you the same hope?

HB: We are absolutely committed to sustainable growth, and prudent stewardship of our natural resources makes a lot of sense in this context. We take this very seriously. DuPont has corporate sustainability goals, which drive each of us to consider the environment in everything we do – whether you are a scientist like myself, an accountant or a plant manager. I’d encourage you to read more about these goals. In particular, there is a speech given by DuPont Chairman Chad Holliday that recaps the history of DuPont and sustainability and how it is embedded in everything that we do.

TH: Do you know enough about the mechanism of how this repellency works to comment as to whether all or some biting insects may develop a resistance?

HB: While we know a fair amount about efficacy, it would be a major overstatement to suggest we understand the mechanism of repellency. We do know that insects do not need to land and contact the Refined Oil to be repelled. There is no evidence to suggest that these natural repellents stimulate resistance.

TH: Related question: could potential product abuse – I’m thinking about large scale spraying of lawns for example – lead to a loss of efficacy?

HB: How does DuPont guard against potential product abuses in general? It’s not clear that widespread spraying would be the most effective means of repelling biting insects. DuPont Refined Oil is not an insecticide, but a repellent. As such we believe it’s likely to be most effective as a topical spray or lotion. That said, we are evaluating its efficacy as an area repellent.

TH: What’s next for the DuPont & Nature “JV?”

HB: Many things. DuPont is committed to the integration of biology with our strengths in chemistry, engineering and materials sciences to develop answers for our customers. And, in addition to our traditional biology-based product lines in Pioneer and Solae, we have made a significant, strategic investment in our Applied BioSciences platform to bring more sustainable, bio-based products to market in the areas of BioMaterials, BioFuels and BioSpecialties.

HB: If I would leave you with one consideration, it is to remind your readers that DuPont will not be commercializing this technology, but is interested in potential partners or licensees for this technology.