Catnip 2
Tapping into the weed power
Catnip 1 covered the look and some of the fun of Catnip, but there’s so much more. Nepeta cataria is in extensive commercial production, not only to entertain our pet cats, but because of its excellent safety profile compared to other insect repellents. We’ll delve into this a bit more as well as sharing some work from our pharmacognosy friends to explain some of the traditional uses of Nepeta cataria.
For the newest readers, Weedom includes research done in countries which rely more on herbal medicine, and bear a more positive attitude towards it than the strongly pharma-connected U.S. institutions and government. The lab equipment and technology used in those countries is generally not as advanced, and often they are tracking active constituents in plant extracts in the same way that was done 2 to 4 decades ago in the U.S., (before we kicked the job of modeling useful drug compounds largely over to computers.) More laborious work certainly does not negate the validity of well designed experiments and reasonable conclusions.
The case of Catnip ability to repel mosquitoes exemplifies the tenet in herbalism that the natural mix of plant constituents provides activity that is different and often superior to that of any purified constituent. This is natural, since the plants adapt and survive with ever changing modifications to their vast array of chemical output. It’s a big job to keep up with them. A 2011 (Birkett et al) study comparing individual nepetalactone isomers, mixtures of them, and unfractionated Catnip essential oil showed the latter to be more effective in repelling insects such as the brown ear tick, the Southern house mosquito and the malaria carrying mosquito (Anopheles gambiae).
The essential oil of Catnip is of relatively low toxicity, (unusual among essential oils). This information comes from animal studies. The median acute lethal dose was 2710 mg/kg in male mice and 3160mg/kg in female mice (This represents the contents of vastly more plant material than could possibly be jammed into a mouse. The essential oil yield is on the order of 0.25% dry weight of a first cutting.) An acute topical administration of 5000mg/kg showed no toxicity in Wistar rats. Acute inhalation at a concentration of 10g/m3 showed no untoward effects in mice up to 2 weeks. New Zealand white rabbits showed some redness of skin (erythema) 3-4 days after application of a half gram of catnip oil. Nasty eye testing in rabbits showed no corneal clouding or inflammation of the iris, but did show initial irritation of the conjunctiva, membranes surrounding the eyeball, which did not persist after 24 hrs.
Yield of the major essential oil components of Nepeta cataria seems not to vary radically with the growth stage. The amounts of nepetalactones remain fairly constant through the vegetative, budding, and full flowering stages of growth, however concentrations of α-pinene, β-pinene, and trans-caryophyllene increase gradually with budding and flowering. Changing type of distillation method affects the composition and array of essential oil components. For example, hydro-distillation produces more aldehyde constituents, and steam distillation produces more of the corresponding alcohols, as well as a higher total yield of essential oils.
Nepetalactones are mysterious substances which are insanely attractive to some species, and repellent to others. They have been found to act as pheromones for diverse species, from aphids to cats. The green lacewing also utilizes nepetalactone as a pheromone, and its larvae feed on the aphids which share this characteristic. Paradoxically nepetalactones also serve as irritants affecting some of the varied TRPA1 receptors found ubiquitously among species, and therefore are effective deterrents to various kinds of mosquitoes, house and stable flies, ticks, bedbugs, moths, roaches, etc. TRPA1 receptors are associated with the ends of nerves that are equipped to sense noxious stimuli. Various species are repelled to different degrees, depending on the individual structure of their TRPA1 irritant receptors. (Humans have this class of receptors, and are not bothered by nepetalactone, but rather, such things as wasabi.) Catnip essential oil from certain strains (containing higher amounts of nepetalactone) was found to be more effective than DEET in repelling bedbugs for 24 hours. Perhaps due to volatility, the effectiveness wears off faster than DEET, which remains more effective 72 hours after application. A less abundant component of Catnip oil, dihydro-nepetalactone was determined, in 1% concentration with isopropyl alcohol, to be twice as effective as DEET, and active for 8 hours.
From a practical standpoint, the insect repellent components of catnip oil can evaporate and dissipate over a short period, so that application of the oils have to be done once to a few times per day, depending on temperature, humidity, and which bug is targeted for repulsion. Researchers are working on ways to overcome this using cyclodextrin complexes (which has met with some success for tick repellancy) to encapsulate the oils, and allow them to be effective for much longer. We could call it sustained release catnip oil. At Weedom, we have been utilizing a rinse off soap product containing catnip and other essential oils for years, because we reside near the mosquito ridden, wet spot that supports our spring peepers. It appears to us that the mosquitos have higher sensitivity to catnip than ticks, which we believe would be more completely discouraged with a leave on product such as a cream or spray. During the Zika virus scare, Robert Tisserand, who wrote the “bible” of essential oil safety, gleaned the literature and came up with his own recommendation for a home made, leave on, mosquito deterrent. It appears to be based on the results of research in tropical regions, and upon his own safety assessment of the oils as leave on products on the skin. He suggested a mixture of 4% turmeric essential oil, 3% peppermint EO, 3% citronella EO, and 90% base oil of your choice. Olive oil or coconut oil were used as diluents in the research. Tisserand also favored catnip oil as highly effective, but found it to be cost prohibitive for most people. At the time of his recommendation, that was very true, but the price is decreasing, and using the degree of dilution seen in research, (from 1% to 10%), it becomes more affordable. If aphids and kitties cling to you, you’ve been warned. If you start experimenting, always dilute essential oils for topical use, try on a small area of skin first, and don’t assume that pets and animals can tolerate human doses.
Catnip has traditionally been added to food products (as are other herbs and spices) with a view towards food preservation. Investigators (Zomorodian, et al) determined that there is sense to this practice based upon their lab findings that the constituents of nepeta cataria can inhibit or kill a variety of food borne, pathogenic bacteria and fungi. Among those tested were Staph. aureus, Listeria monocytogenes, E. coli, various Salmonella species, and Aspergillus species. There were no significant differences in potency of the oils extracted during various life stages of catnip, as was expected from the small amount of variability in essential oil constituents among these stages. Also, there was no difference in the effectiveness of the oils to inhibit antibiotic-resistant bacterial strains vs. antibiotic susceptible strains. The antibacterial effects of the oils are likely via different mechanisms than conventional antibiotics, and it has been suggested that the nepetalactones were largely responsible for the effectiveness. Other experiments showed good activity of the catnip essential oil against oral bacteria associated with dental issues, and Candida species. The concentrations required for inhibiting and for killing microbes in the lab, compared favorably with some of the antibiotics which are in current medical use. Nepeta citriodora has been more popular as a food and drink additive for reasons of flavor preference. The neral and citral constituents (also found in lemongrass and citrus peels), smell and taste much better to us, but cats are not impressed. Considerable antimicrobial activity has also been found in the essential oil of this relative of catnip. Research is scant regarding the ability of catnip oils to exert anti-infective actions to treat human disease, but considering their potency and low toxicity to mammals it’s certainly worthy of formal investigation.
In Catnip 3 we’ll be telling your about this weed’s activity as “Viagra” for rats, nervine, relaxant, anti-cancer potential and more. Keep in mind that the mint family, Laminaceae is a huge part of our nervine and anti-infective armamentarium of herbs. We’ll be presenting many more members of that botanical family tree.
We invite you to relaaaaax with Kitties of Weedom on Catnip , fun stuff from our video bootcamp. Advice is welcome as we learn.
It’s challenging to convey the real evidence that plants build defense systems for themselves which we can use, in the unrefined state, for our own benefit. Questions and feedback are welcome. Interactions with you will surely help to improve the writing, inspire more content, and make it accessible to more people.
Where We Dig
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