Repellent compositions for insects

Abstract

Repellent compositions for insects are disclosed, in particular mosquitoes, containing N,N-dibenzyl-meta-toluamide aass aann active ingredient, a solid substance which can advantageously be formulated in various forms which can be used both topically and by diffusion into the environment, for example by means of candles.

Description

[0001] REPELLENT COMPOSITIONS FOR INSECTS

[0002] The present invention relates to repellent compositions for insects, in particular mosquitoes, characterized in that they contain N,N-dibenzyl-meta-toluamide as an active ingredient.

[0003] Prior art

[0004] Mosquitoes are vectors of numerous infectious diseases which affect humans. In addition to malaria, which is endemic in many geographical areas, diseases previously confined to predominantly tropical or subtropical areas are spreading, a complex and worrying phenomenon influenced by several factors including climate change, globalization and the increase in international travel.

[0005] These include Dengue, caused by a virus, transmitted by Aedes aegypti and Aedes albopictus mosquitoes, Zika, Chikungunya, yellow fever, West Nile virus from Culex mosquitoes, lymphatic filariasis caused by parasitic worms and transmitted by Culex, Anopheles and Aedes mosquitoes.

[0006] To prevent mosquito-borne diseases, it is critical to adopt individual protection measures, such as the use of insect repellents, mosquito nets, and protective clothing, as well as reducing mosquito breeding sites by eliminating water stagnation.

[0007] The most widely used repellents for insects, in particular for mosquitoes, are generally based on several active ingredients which have demonstrated efficacy.

[0008] DEET (N,N-diethyl-meta-toluamide) is one of the most effective and widely used repellents. It is available in various concentrations and can protect for several hours, depending on the concentration. As an alternative to DEET, picaridin (also known as icaridin), against a wide range of insects and characterized by a less strong odour with respect to DEET. Other known repellents include eucalyptus citrate oil (OLE) or p-menthane-3,8-diol (PMD), IR3535 (ethyl butylacetylamino propionate), lemongrass oil, one of the best known natural repellents, neem oil, another natural repellent which has shown some efficacy against mosquitoes, although some people may find its odour unpleasant.

[0009] These ingredients are found in various repellent products, including sprays, lotions, wipes, and bracelets. The choice of repellent depends on various factors, including the duration of protection desired, personal preferences for natural or synthetic ingredients, and skin sensitivity.

[0010] In addition to topical use, the repellents can also be spread in the environment by means of candles and coils. Essential oils such as lemongrass, eucalyptus, lemon eucalyptus, lavender and geranium oils are commonly used in candles, often in mixtures.

[0011] The anti-mosquito coils are mostly based on pyrethroids such as allethrin, D-allethrin, exbiothrin, transfluthrin.

[0012] The candles are lit and release the smoke and odour of the essential oils, creating a barrier which mosquitoes find unpleasant. They are generally used in gardens, terraces or balconies.

[0013] The coils are lit and burn slowly, releasing smoke which contains pyrethroids. This smoke is effective at repelling and killing mosquitoes in a confined area.

[0014] Both methods are useful for reducing the presence of mosquitoes in outdoor environments, but their effectiveness can vary depending on environmental conditions, such as wind and mosquito population density.

[0015] Description of the Invention

[0016] It has now been found that N,N-dibenzyl-meta-toluamide is an effective inducer of anosmia in hematophagous insects, in particular mosquitoes. The inhibition of smell impairs the mosquito's ability to detect a warm-blooded animal, in particular a human being. In fact, it is known that mosquitoes identify their prey mainly by means of smell, detecting even at a distance of several tens of metres the emission of compounds such as carbon dioxide and lactic acid emitted by the human metabolism.

[0017] The activity of N,N-dibenzyl-meta-toluamide appears surprising as a solid substance at room temperature, significantly less volatile than N,N-dimethyl-meta-toluamide. This feature is advantageous, especially for an easier preparation of candles for the environment.

[0018] The invention therefore relates to the use of N,N-dibenzyl-meta-toluamide as a repellent for insects, in particular mosquitoes.

[0019] N,N-Dibenzyl-meta-toluamide of formula I is known and can be prepared by conventional synthetic methods.

[0020] Formula I N,N-dibenzyl-meta-toluamide can be used either for topical use, for example in the form of sprays, lotions, wipes, ointments, impregnated bracelets, or by diffusion in environments in the form of candles, diffuser plates or coils. The candles are particularly effective, guaranteeing a prolonged and constant diffusion of the active ingredient in the environment, with a particularly marked repellent effect.

[0021] A further object of the invention consists of compositions in the form of candles, diffuser platelets or coils comprising N,N-dibenzyl-meta-toluamide as an active ingredient.

[0022] The concentration by weight of N,N-dibenzyl-meta-toluamide is preferably between 1 and 30% by weight, more preferably between 1 and 15%.

[0023] The compositions of the invention can also contain, in addition to conventional vehicles and excipients, one or more repellents selected from essential oils and natural pyrethroids. The candles can be prepared by adding the active ingredient in the solid state to the molten wax or paraffin which constitutes the candle.

[0024] The invention further relates to a method for repelling hematophagous insects, in particular Culex, Anopheles an Aedes mosquitoes, which comprises both the diffusion into the environment of N,N-dibenzyl-meta-toluamide by means of diffusers, candles, coils, electrical devices and the like and the protection of humans and animals both with application on clothing, on hair and directly on the skin of humans and animals.

[0025] N,N-dibenzyl-meta-toluamide was negative in the Ames test for genotoxicity and the rabbit dermal sensitization test.

[0026] The invention is now illustrated in more detail in the following example.

[0027] EXAMPLE 1

[0028] Tests were carried out with both paraffin and soy wax candles with solidification temperature 58-60°C, considering that the melting point of the substance is 70-74°C and so as to allow a passage in the aeriform phase of the substance itself, also "transported" by the phase change of the wax. Candle diameter 75 mm, approx. 45 mm high, average weight 75 g. in cylindrical glass 65 mm tall.

[0029] The content of repellent substance used in the tests was 1%, 2%, 10% on the weight of the candle. Near the candle, whose temperature simulates a warm body with respect to the surrounding environment, a source of carbon dioxide (aqueous solution of citric acid and sodium bicarbonate) and a garment impregnated with sweat were placed in order to attract insects.

[0030] The tests were carried out at dawn and dusk in a lake area with clean and even still waters typically infested with firstly Anopheles mosquitoes and secondly Culex mosquitoes, in late spring (late May) and an average daytime ambient temperature of 22°C in the typical breeding period in which the female mosquito needs blood for the eggs to mature.

[0031] The tests were performed by visual inspection and counting insects caught on adhesive tablets. The repellency effect in the open environment remained constant even with the lowest amount 1% by weight, with a measured repellency radius of about 4 metres in diameter in the plane with a cone of about 3 metres in height from the source in the absence of air currents. The duration of the test was 90 minutes. In the aforementioned volume, an average of 10 insects were spotted, of which 50% were collected on the adhesive tablets: fewer than 5 individuals for candles at 10% by weight and in any case compatible with an adequate repellency effect for both the 2% by weight and 1% by weight candles.

[0032] EXAMPLE 2

[0033] Practical repellency tests were carried out with the usual test on volunteers who place the forearm on which the repellent is spread in a special plexiglass cage, in which an adequate number of insects are placed. The tests are repeated for 3 minutes at 30 minute intervals until the first puncture occurs. Formulations were used in which the repellent, dosed at 5, 10 and 15% by weight, was suspended in an alcoholic solution, applying a single pass on the upper part of the forearm with a non-woven fabric wipe on which the repellent was gently absorbed.

[0034] The ensured protection exceeded 3 hours with the formulation at 10% by weight and more than 5 hours with the formulation at 15% by weight.

Claims

CLAIMS1. Use of N,N-dibenzyl-meta-toluamide as a repellent for insects, in particular mosquitoes.

2. Use according to claim 1, wherein the N,N-dibenzyl-meta-toluamide is administered topically.

3. Use according to claim 2, wherein the N,N-dibenzyl-meta-toluamide is administered by means of formulations in the form of sprays, lotions, wipes, ointments, impregnated bracelets.

4. Compositions according to claim 1, for diffusion into environments.

5. Insect repellent compositions in the form of candles, diffuser platelets or coils comprising N,N-dibenzyl-meta-toluamide as an active ingredient.

6. Compositions according to claim 5 comprising one or more repellents selected from essential oils, natural pyrethroids.

7. Compositions according to claim 5 or 6, wherein the concentration by weight of N,N- dibenzyl-meta-toluamide is between 1 and 30% by weight, preferably between 1 and 15.

8. A method for repulsion of hematophagous insects comprising diffusing N,N-dibenzyl- meta-toluamide into the environment.

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