CA2325372A1 - Utilization of natural and/or synthetic quinic acid and/or precursors thereof as insect repellents - Google Patents

Abstract

The invention relates to the utilization of natural and/or synthetic quinic acid (1,3,4,5-tetrahydroxycyclohexane carboxylic acid) and/or precursors thereof as insect repellents.

Description

Use of natural andlor synthetic chinic acid andlor precursors thereof als insect repellents The present invention relates to an insect repellent against flying, creeping, biting and sucking insects and other related species of articulates (Arthropodes), like mites and ticks (Acarina), as well as spider animals (Arachnids). Such insect repellents are commonly called repellents.
Repellents are chemical substances having a repulsive effect on articulates, particularly on insects, which are noxious and pestering to man and animal.
Their use has a great practical importance in human and veterinary hygiene where they protect man and animal against attacks by bloodsucking, biting or otherwise annoying arthropodes. When repellents have to be applied directly to skin, coat or apparel it is required that these are well tolerated by skin, non-toxic, particularly not resorbable, perspiration and light save and perfect in cosmetic respect. Moreover, the protection of the treated skin areas is to be as broad as possible, i.e. they should act against the largest possible number of harmful and annoying insects.
The practical utilization of repellents and their benefit is exlained solely by the fact that statistically every thirty seconds a person dies from the consequences of insect bites and number and extent of all other consequential manifestations of attacks of insects to man and animal remain unrecordable by number. Therefore only the transfer of dangerous diseases like malaria, yellow fever, dengue fever and filariasis should be refered to as a causal factor for the benefit of repellents.
All repellents so far known present the common chemical-physical property of evaporating more or less quickly at room temperature whereas the intensity and duration of their protective effect depend essentially from two factors:

1. The more volatile a substance, the more intensive its protective effect, in particular shortly after application, however, the duration of its protection is proportionally shorter. In this respect, essential oils and natural compounds comprising these oils should be particularly mentioned and notice should be made how in earlier times they were the only repellents available, like i.e. garlic, pennyroyal oil and the juice of ripe tomatoes resp.
the essential oils citronella, bergamot, eucalyptus, lavender, clove, nutmeg, cinnamon and others.
2. The slower the evaporation proceeds at room temperature, the longer the protective effect lasts. In connection therewith, it should be taken into account that substances which do not evaporate to a sufficient extent cannot establish a durable protective shield capable to disturb to the attracting mechanism of the parasites. These compounds are ill appropriate when not totally unsuitable to be used as repellents.
Consequently, the following ones of the extremely extensive group of repellent acting, synthetic compounds, which are essentially part of the compound classes of amides, alcohols, esters and ethers have proved to be particularly effective and have therefore prevailed on the market : N,N-diethyl-m-toluamide (DEET), dimethylphthalate (DMP) and butylacetamido propionic acid ethyl ester (BAP, 3535) and combinations thereof. Other compounds are not enough effective or involve massive toxicological risks and are only ocasionnally to be found on the market or have already completely gone out. However, for some time past, the medical and in particular the dermatological experts have increasingly debated about the tolerance and the toxicological risks of the above mentioned synthetic repellent active substances since, for reason of their molecular structure, they are able to diffuse through the skin resp. to be resorbed by it.
Therefore, the object of the present invention is to provide an effective insect repellent based on natural substances and on substances identical to natural substances presenting the minimal toxicological risk and having a high effectivity over a long period.
The object is solved by the use of natural and/or synthetic chinic acid and/or precursors thereof. Preferably, the chinic acid is dissolved in at least one suitable, toxicologically harmless, natural and/or identical to natural and/or synthetic carrier.
Natural andlor synthetic chinic acid andlor precursors thereof can be used for the protection against creeping, biting, sucking and infecting parasites, particularly insects and related species.
The active substance used in the present invention is chinic acid (1 R, 3R, 4S, 5R)-(1,3,4,5,-tetrahydroxycyclohexane carbonic acid) with the structure H HO OH COOH and the total formula C,H,ZOs.
OH
The molecular weight is 192.17.
Preferably, the chinic acid is dissolved in a carrier of natural or synthetic origin, preferably water. The preferred amount of active agent is 0.1 to 50 wt.
of chinic acid in the carrier.An amount of 5 to 30 wt. % of china acid is particularly preferred.
The carrier used in the present invention can be a mixture of different carriers. The use of a mixture of water with glycerol, alcohols or propane diols is particularly preferred. More particularly preferred is the use of a mixture of 0.1 to 50 wt. % chinic acid in 50 to 99.1 wt. % of a mixture of 0.1 to 99.9 wt.
water and 0.1 to 99.9 wt. % of the other carrier.
The china acid used is prepared according to known methods (extraction and recrystallisation) using its natural sources, chinic bark (Cortex Chinae), different species of chinona (Rubiaceae), coffee- beans, sugar-beets, meadow hay, gooseberrys and blackberrys as well as leafs of bilberrys and cranberrys. Chinic acid can also be prepared synthetically and used.
Precursors of chinic acid can also be used. A preferred precursor is their dehydrated form, the shikimi acid (3,4,5-trihydroxy-1-cyclohexane carbonic acid). In the following all these compounds will be designated china acid for simplicity.
In further preferred embodiments 0.1 to 50 wt. % of chinic acid and 50 to 99.9 wt.% water, or 0.1 to 50 wt. % chinic acid, dissolved in a mixture of glycerol and water or of 1,2-propylene glycol and water, are used. In this case, use of to 30 wt. % of chinic acid is particularly preferred. The mixture ratios of the different carriers are as given generally above.
Moreover, china acid can be used in the form of an emulsion, dispersion, lotion, creme, gel or solution. For the preparation of these types of applications, the usual methods of preparation can be employed. The usual substances and additives can also be employed. These substances and additives comprise the typically used solvents, solvent accelerators, emulsifiers, solubilizers, wetting agents, anitfoamants, salt formers, buffers, gelatinizing agents, thickening agents, film-forming agents, binders, lubricants, detackifiers, flow regulation agents, humectants resp. desiccants, fillers as well as auxiliary agents, like antioxidants, preservatives, odor correctives and coloring agents.
The wording "emulsion" includes all dispersed systems of two or more liquids not miscible with each other whereby the emulsion components may be compounds solid at room temperature. These emulsions can be macro or micro emulsions. Typically, water-in-oil or oil-in-water emulsions may be used.
For the reduction of the interfacial surface work (work needed for the emulsification) emulsifiers are employed. Emulsifiers are usually surface active compounds, typically with hydrophilic end groups. Typical examples therof comprise:
a) anionic emulsifiers, i.e. emulsifiers with carboxylic, sulfonic, sulfate, phosphate, polyphosphate, lactate, citrate, tartrate, glucose or polyglucose end groups;
b) cationic emulsifiers, i.e. emulsifiers with amine salt or quaternary ammonium end groups;
c) amphoteric and zwitterionic emulsifiers, i.e. emulsifiers with zwitterionic end groups or betain end groups; as well as d) non-ionic emulsifiers, i.e. emulsifiers with alcohol, polyether, glycerol, sorbitol, pentaerythritol, saccharose, acetic acid and/or lactic acid residues as end groups.
All emulsifiers contain additionally lipophilic end groups like alkyl or alkenyl rests, each of which are linear, branched or cyclic as well as aryl or alkylaryl residues.
Further hydrophilic side groups like hydroxyl, ester, sulfamide, amide, amine, polyamide, polyamine, ether, polyether, glycerol, sorbit, pentaerythrite or saccharose end groups can be comprised.
The wording "gels" includes form stable, easily deformable systems being rich in liquids of at least 2 components. Usually these two components are a) a liquid and b) a solid, colloid dispersed compound like gelatine, silicic acid, montmorillonites, bentonites, polysaccharides, polyacrylic acids, pectins etc.
According to the present invention, a completely harmless active substance prepared from natural raw materials is used which can be formulated in equally harmless, cosmetically and pharmaceutically well known and toxicologically totally safe solvents.

Additionally, the use according to the present invention offers in contrary to all other compounds known so far a completely new acting mechanism. This is not a mechanism based on a permanent evaporation cloud extending above the skin and masking the position receptors which are secreted from the skin, the effect of such a mechanism being subject to variations depending on the circumstances. The use of china acid according to the present invention blocks in a constant and permanent reaction with precursors permanently produced or secreted and being positioned on the skin and being soluble in the solvent of the repellent the formation of receptors on the skin, the coat or garments lying on top thereof indepently of variations of the surrounding conditions. Said precursors are e.g. ammonia, lactic and butyric acid, carbon dioxide and certain amino acids (like cystine and glutamine). It is thus not an evaporation cloud masking these already formed receptors formed which keeps off parasites but their formation on the skin is already prevented rendering the areas treated therewith unattractive for destructive insects.
The chinic acid used according to the present invention cannot for reason of its chemical and physical properties penetrate into the skin. Consequently threre exists no factor of risk for the health.
The following examples will explain the invention.
1. Examples of formulations for use of chinic acid according to the present invention TS (I) 10.00 wt. % chinic acid 20.0 wt. % water 70.0 wt. % 1,2,3-propanetriol (glycerol) TS (II) 5.00 wt. % chinic acid 57.00 wt. % water 10.00 wt. % Cetylstearyl-polyglycosides 28.00 wt. % glycerol TS (III) 2.00 wt. % chinic acid 3.00 wt. % glycerol 2.00 wt. % propane-1,2-diol (1,2-propylene glycol) 3.00 wt. % ethanol (ethyl alcohol) 90.00 wt. % water 2. Examples of application The repellents (I) and (II) were tested with two different persons whereas a commercial product was used as reference (KIK AKTIV - 30 % DEET).
Experiment:
The right forearm of a test person was treated on an area of about 250 cmZ
with the respective test compound - TS (I) or (II). An amount of 2 ml of the respective test compound was equally spread. The treated area of the forearm was sealed on both ends with an insect save adhesive tape and provided with a short plastic tube. The untreated hand was covered with a thick glove and served thus at the same time as a control for the biting activity of the laboratory animals. The left forearm was treated in the same manner with a reference product (REF). As laboratory animals about 300 to 400 yellow fever insects (Aedes aegypti), almost exclusively little females, were employed in a breeding cage of 40x40x40 cm.
For the test, the forearms and the hands, successively, first the left then the right, were kept into the cage with insects and during 10 minutes, the number of insects which:

g ( a ) tried to bite through the glove (positive control), ( b ) flied closer than 3 cm towards the treated area, ( c } landed and remained sit on the treated area longer than 2 seconds, and ( d ) bit into the treated area and sucked blood, was noted.
3. Results: Test person (1 ) time afterdurationlanding insects landing number applica- of on flying insects of tion exposureglove towards (c) bites (a) (b} TS (d) TS TS (I) TS
(I} (I) REF (I) REF REF REF

1 h 10 min 100 100 0 0 0 0 0 0 2 h 10 min 100 100 0 0 0 0 0 0 3 h 10 min 100 100 0 0 0 0 0 0 4 h 10 min 100 100 0 2 0 0 0 0 h 10 min 100 100 0 4 0 1 0 0 6 h 10 min 100 100 2 12 0 7 0 0 7 h 10 min 100 100 1 10 0 3 0 0 8 h 10 min 100 100 1 8 0 ~ 3 0 0 ~

Test person (2) time afterdurationlanding insects landing number applica- of on flying insects of tion exposureglove towards (c) bites (a) (b) TS (d) TS TS (I) TS
(I) (I) REF (I) REF REF REF

1 h 10 min 100 100 0 0 0 0 0 0 2 h 10 min 100 100 0 0 0 0 0 0 3 h 10 min 100 100 0 0 0 0 0 0 4 h 10 min 100 100 5 3 1 1 0 0 h 10 min 100 100 8 8 2 1 0 0 6h 10 min 100 100 14 10 6 7 0 0 7 h 10 min 100 100 10 12 4 2 0 0 8 h 10 min 100 100 8 10 4 6 0 ~

The number of insects landing on the gloves was estimated since due to the varying high numbers an exact evaluation was impossible.
The effectivity of a compound results primarily from the ratio of insects landing on the glove and willing to bite to the other values.
The number of biting insects is the decisive factor for the period of effectivity and therewith in the tropics indirectly also for the risk of infection. The tested compounds ensure protection for more than 8 hours. As can be taken from parameters b) and c) there is a certain number of insects even with the utilization of compounds used according to the present invention flying towards and landing; however, they do not bite. A strong repelling effect can be attributed to all tested compounds whereby the TEST PRODUCT (I) showed the best effect. Particularly, the extremely low number of insects flying towards and the fact that not a single insect landed shows the superior effect of the use of chinic acid according to the present invention having an amount of 10% of active substance vis-a-vis the commercial reference compound having an amount of 30% of active substance. Therefore, the advantage of preventing the formation of receptors directly on the skin as compared with the covering of receptors is particularly clearly demonstrated.
Even TEST PRODUCT (II) with only one sixth of the content of active substance of the reference results in a comparable effect.
For the verification of these laboratory results a open land experiment was conducted with 20 test persons over a period of 5 days in a river meadow highly burdened with insects and gadflys.
The preparation of the test persons was effectued in the same manner as in the laboratory experiment. The persons who were to be submitted to the tests with insects were exposed exclusively from sunset on at temperatures of from 18 to 28°C, relative humidity of from 50 to 95% and wind speeds below 1 mls and the persons to be submitted to the tests with gadflys were exposed exclusively during the day with the above conditions.
For each experiment, groups of five test persons were formed whereof one person served as an untreated control, 2 persons were treated with the TEST
PRODUCT (I) and 2 persons with the REFERENCE. The untreated control served as measurement for the willingness of insects or gadflys to bite and was exposed each time for one minute.
Average values were calculated for all experiments, whereby the insects landing on the gloves were estimated and the insects landing on the remaining protective garment of the test pesons were not taken into consideration.

Test results INSECTS, particularly Culex pipiens 1. Average untreated control over 1 min. exposure landing on gloveinsects flying landing insectsnumber of bites towards 2. Average REFERENCE, exposure 8 hours 10 minutes each, numbers refer to 10 minutes landing on gloveinsects flying landing insectsnumber of bites towards 3. Average TEST PRODUCT (I), exposure as 2.
landing on gloveinsects flying landing insectsnumber of bites towards The comparison over an average test time of 10 minutes shows that an untreated person would have been bitten theoretically 420 times during that time whereas both the REFERENCE and TP (I) remained without bite.
In a comparison of REF and TP (I) it is again noticeable that the TEST
PRODUCT shows a rate of annoyance by far lower (numbers of insects flying towards and landing) and therewith the result of the laboratory experiments could be verified.

Test results GADFLYS particularly Haematopoda pluvialis In this case, only the numbers of bites could be evaluated since gadflys fly towards an area in a stretch without particular search flight, land, bite, suck with lightning speed a drop of blood and start again.
Average of bites of gadflys at 1. untreated control over 1 min. exposure: 2 2. REFERENCE against TEST PRODUCT (I), 10 min. exposure timel hour, average of all test times Q~ Gadfly bites at Time after applicationREF. TP (I) 1. hours 0.0 0.0 ~ 2. hours 0.0 0.0 if 3. hours 0.1 0.0 4. hours 1.0 0.0 5. hours 2.0 0.1 6. hours 3.0 1.0 This experiment undertaken 12 times during a cross test also shows that the effect of the test product used according to the present invention lasts at least about two hours longer than the effect of the reference commercial product.
For the examination of the effectivness of the repellent effect against ticks as a typical representative of Acarinae which are the by far most dangerous representatives of this genus a five days lasting open land test was conducted. From a house for the protection of animals three shepherds dogs, male, of almost the same size and the same weight with three dog's masters were provided who walked the dogs daily each time for four hours through a known tick contaminated area. Constantly, on a daily basis each 1 dog was labelled with K (control), TP (I) and REF. The dog and the leader belonging to it were each treated on the whole surface of their bodies with about 10 ml TEST PRODUCT (I) and REFERENCE. An untreated dog served in each case as control whose masters, although inoculated against FSME, was treated with REFERENCE to encounter the risk of a transfer of borreliosis by possible tick bites.
After each four hour walk daily, the test animals and their masters were thorougly examined for the presence of ticks, these were documented and collected in labeled glasses and observed for another 72 hours.
Results:
1. untreated control - during five experiment days 86 ticks, 68 thereof of the genus I.rizinus and 18 of R.sanguineus- whereby the respective stages (adults and nymphs) were not differentiated - were found on the dogs. All ticks survived the 72 hours observation afterwards.
On the articles of clothing of the dog's masters, a total of 24 ticks were found, whereby, in comparison to the untreated dog, no tick could be found on the skin of the dog's master or bored into it. The 24 ticks survived the observation time afterwards as well.
2. REFERENCE - on the dog a total of 6 ticks were found and on the clothing of the dog's master 19 ticks (adults and nymphs of 21 I.ritinus and 4 R.sanguineus) were found whereby, however, none of them were on the skin or bored into it. All ticks survived the 72 hours observation afterwards. The repellent time (duration of effect) of the reference product can therefore be given as 4 hours whereby, however, the total of 6 ticks would surely have bored into the coat of the dog with a decrease in effect of the product since they survived the observation time afterwards.

3. TEST PRODUCT (I) - during the whole 5 days experiment time, no tick was found on the dog.
On the clothing of the dog's masters (all wearing a long-sleeved light shirt and white linen trousers) a total of 5 ticks of the genus I.rizinus were found, 3 of which did not survive the observation time.
After the 72 hours observation time, the total of 110 ticks of the untreated control and the ticks of test product (TP I) were immersed for 5 minutes into TEST PRODUCT (I) according to the instructions of the immersion test of the ectoparasites screening and were all dead 24 hours later. The 25 ticks which survived the observation time of REFERENCE were immersed as above into the reference product for 5 min.and survived additional 72 hours and were then by immersion over 1 min. in TP (I) after additional 24 hours classified as being dead.
That experiment demonstrated that TEST PRODUCT (I) not only shows a protection period against ticks lasting at least 4 hours but also that the ticks were reliably killed after having been brought in contact with the product and that the latter is therefore superior to the ususal in trade, accepted reference as regards the absolute protective effect against tick bites.
As support for the surprisingly occuring mortal effect of the repellent used according to the present invention, the following screenings were conducted with different insects as follows:
1. TEST PRODUCT (III) in comparison with a 2. commercial insect repellent (REFERENCE) comprising as active substance according to the label 0.05 % Bio Allethrin and 0.25 % Permethrin in a watery emulsion.
Acrylic tubs with L=50 cm, B=30 cm, D=25 cm, whose floors were painted IS
with each 1 ml TB (III) and REF, respectively, served as test containers. Both into the containers treated with TB (III) and into the containers treated with REF each 10 test insects were placed onto the floor and after 1 minute contact time transfered into an untreated container and observed for another 48 hours.
Test insects:
I. cockroaches (Blatella germanica) II. ants (Lasius niger) Results:
Both the test insects brought into contact with TP (III) and those brought into contact with REF were all dead after 48 hours. A further observation over 72 hours brought not any reanimation so that the use of chinic acid according to the present invention shows a comparable effect to the commercially accepted reference product.

Claims (8)

Claims:

1. Use of natural and/or synthetic chinic acid (1,3,4,5-tetrahydroxycyclohexane carbonic acid) and/or precursors thereof as parasite repellents.

2. Use according to claim 1 characterized in that the chinic acid is dissolved in at least one appropriate carrier.

3. Use according to claim 2 characterized in that 0.1 to 50 wt.% of chinic acid is dissolved in 50 to 99.9 wt.% carrier.

4. Use according to claim 2 or 3 characterized in that the carrier is water.

5. Use according to any one of claims 2 to 4 characterized in that glycerol, alcohols or propanediols are comprised.

6. Use according to claim 5 characterized in that 0.1 to 50 wt.% chinic acid, 0.1 to 99.8 wt.% water and 0.1 to 99.8 wt.% of a further carrier are comprised.

7. Use according to any of claims 1 to 6 in form of emulsions, dispersions, lotions, cremes, gels or solutions.

8. Use according to any of claims 1 to 7 for protection against flying, creeping, stinging, biting and sucking parasites and annoying animals.