Efficient mosquito repellent liquid and preparation method thereof

Abstract

According to the efficient mosquito repellent liquid and the preparation method thereof, trans-menthanediol serves as a main active component, cis-menthanediol can serve as a secondary active component, the total content of trans-menthanediol and cis-menthanediol is 6%-20%, and the effective repelling time of the mosquito repellent liquid is remarkably prolonged; in addition, by increasing the proportion of the trans-menthanediol with the configuration, the effective mosquito-repelling time of the mosquito-repelling liquid is remarkably prolonged under the same concentration; on the basis, a small amount of eucalyptus citriodora essential oil is added to serve as a synergistic component, synergistic interaction can be further achieved, the continuous mosquito repelling performance is improved, and the whole formula is free of toxic and side effects and high in safety.

Description

TECHNICAL FIELD

[0001] The present application relates to a mosquito repellent product, in particular to a high-efficiency mosquito repellent liquid and a preparation method thereof. BACKGROUND

[0002] Malaria transmitted and caused by mosquitoes harms 350 million to 500 million people and causes more than 1 million deaths every year. Mosquitoes are the vectors of infectious diseases, especially in tropical regions, and many infectious diseases are often transmitted to humans by mosquitoes, seriously endangering human health. People usually rely on reducing the number of infected persons for prevention and control. To reduce the risk of infection and reduce the discomfort caused by mosquitoes, it is necessary to find safe and effective mosquito repellent products. The active ingredients of the common mosquito repellents on the market are N, N-diethyl-m-toluamide (DEET), ethyl 3-[(acetyl)(butyl)amino]propanoate (IR3535), ecarizine (RS)-sec-butyl (RS)-2-(2-hydroxyethyl)piperidine-1-carboxylic acid and other synthetic active substances. However, most of the mosquito repellents on the market are single agents, and the effective period is not very long, so it is the main purpose of the present application to develop a long-acting and composite mosquito repellent. SUMMARY

[0003] In order to solve the problem of short effective period of mosquito repellent in the prior art, the present application discloses a high-efficiency mosquito repellent liquid, which uses trans-menthyl alcohol as the main active ingredient and lemon eucalyptus essential oil as the synergistic ingredient, so that the effective mosquito repellent time of the prepared mosquito repellent liquid is significantly prolonged, and there is no toxic side effect.

[0004] To achieve the above-mentioned application purposes, the technical solutions adopted by the present application are as follows: A high-efficiency mosquito repellent liquid, which uses trans-menthyl alcohol as the main active ingredient and lemon eucalyptus essential oil as the synergistic ingredient.

[0005] Optionally, the high-efficiency mosquito repellent liquid further comprises a secondary active ingredient, and the secondary active ingredient is cis-menthyl alcohol.

[0006] Optionally, the mass ratio of the trans-menthyl alcohol and the cis-menthyl alcohol is 3:(0-2), and the average effective repellent time is not less than 5.74 hours.

[0007] Optionally, the mass ratio of the trans-menthyl alcohol and the cis-menthyl alcohol is 3:(0-1), and the average effective repellent time is not less than 5.88 hours.

[0008] Optionally, the total content of the trans-menthyl alcohol and the cis-menthyl alcohol is 6%-20%.

[0009] Optionally, the mass ratio of the total mass of the trans-menthyl alcohol and the cis-menthyl alcohol to the mass of the lemon eucalyptus essential oil is 8:(1-5).

[0010] Another object of the present application is to provide a preparation method of the high-efficiency mosquito repellent liquid as described above, comprising the following steps: S1: taking citronellal with a single configuration as a raw material to obtain a mixture of menthone glycerol acetal under the catalysis of an acid; S2: obtaining cis-menthone glycerol acetal by recrystallization; S3: obtaining trans-menthone glycerol acetal by column chromatography after concentrating the filtrate; S4: mixing the cis-menthone glycerol acetal and the trans-menthone glycerol acetal, and adding lemon eucalyptus essential oil to obtain the mosquito repellent liquid.

[0011] Optionally, the cis-menthone glycerol acetal is at least one selected from (1R)-(+)-cis-menthone glycerol acetal, (1S)-(-)-cis-menthone glycerol acetal and (±)-cis-menthone glycerol acetal.

[0012] Optionally, the trans-menthone glycerol acetal is at least one selected from (1R)-(-)-trans-menthone glycerol acetal, (1S)-(+)-trans-menthone glycerol acetal and (±)-trans-menthone glycerol acetal.

[0013] Optionally, the citronellal is at least one selected from S-citronellal, R-citronellal and (±)-citronellal.

[0014] The present application has the following beneficial effects: Compared with the traditional mosquito repellent liquid mainly containing racemic cis-menthone glycerol acetal, the high-efficiency mosquito repellent liquid provided by the present application significantly prolongs the effective repellent time of the mosquito repellent liquid by taking (1R)-(-)-trans-menthone glycerol acetal with a specific configuration as the main active ingredient and supplementing with (1R)-(+)-cis-menthone glycerol acetal; in addition, by increasing the proportion of the trans-menthone glycerol acetal with the configuration, the effective mosquito repellent time of the mosquito repellent liquid is significantly improved at the same concentration, and there is no toxic side effect; on this basis, a small amount of lemon eucalyptus essential oil is added as a synergistic ingredient, which can further synergize to improve the continuous mosquito repellent performance, and the whole formula has no toxic side effect and is safe. DETAILED DESCRIPTION

[0015] The examples described below are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application, and all other examples obtained by a person of ordinary skill in the art based on the examples of the present application without creative labor belong to the scope of protection of the present application.

[0016] General repellents on the market usually contain N, N-diethyl-m-toluamide (DEET), ethyl 3-[(acetyl)(butyl)amino]propanoate (IR3535), Ecampridine (RS) -sec-butyl (RS) -2- (2-hydroxyethyl) piperidine-1-carboxylic acid and other synthetic active substances; however, these active substances have potential defects such as skin irritation, plastic corrosion and environmental residues, prompting regulators and consumers to turn their attention to natural alternatives.

[0017] The p-menthane-3,8-diol (PMD) is currently the only natural active component of insect repellent allowed by the United States and the European Union, and the commercial repellent repellent containing p-menthane-3,8-diol as an active ingredient is also on the market in China; it exists in lemon eucalyptus leaf oil extract and is a monoterpene with three asymmetric chiral centers. In theory, such compounds should have 8 stereoisomers, but natural p-menthane-3,8-diol exists as a mixture of 4 chiral isomers.

[0018] Current studies have shown that cis-p-menthane-3,8-diol is much more active than trans-p-menthane-3,8-diol in preventing mosquitoes, and high-quality p-menthane-3,8-diol contains no or little trans structure. To further verify this conclusion, it is necessary to synthesize these different configurations of p-menthane-3,8-diol and systematically screen their activities.

[0019] The present application prepared (1R)-(+)-cis-p-menthane-3,8-diol, (1S)-(-)-cis-p-menthane-3,8-diol, (±)-cis-p-menthane-3,8-diol, (1R)-(-)-trans-p-menthane-3,8-diol, (1S)-(+)-trans-p-menthane-3,8-diol and (±)-trans-p-menthane-3,8-diol according to the following method: S1: Add magnetic sub and deionized water in a single mouth bottle, slowly drop sulfuric acid under stirring state; after slightly cooling, add single configuration citronellal to the above dilute sulfuric acid, start heating, keep at 50-60 DEG C for 6-7h, after GC detection, add saturated sodium bicarbonate aqueous solution, after separation, the water phase is extracted with ethyl acetate, and the combined organic phase is dried with anhydrous sodium sulfate; after rotary evaporation, add n-hexane to the crude product, freeze in the refrigerator, and then filter the solid to obtain cis-p-menthane-3,8-diol; S2: The filtrate of the above step is concentrated and purified by column chromatography to obtain trans-p-menthane-3,8-diol.

[0020] The mosquito repellent effect of (1R)-(-)-trans-menthodiol is optimal through the research results of different configurations of 10% menthadiol. Based on the finding, the present application screens the mosquito repellent effect of different cis-trans ratios of the configuration, and the mass ratio of trans-menthodiol and cis-menthodiol is preferably 3:(0-2); further, the mass ratio of trans-menthodiol and cis-menthodiol is preferably 3:(0-1), and the average effective repellent time is not less than 5.88 hours; in addition, under the same concentration, the effective mosquito repellent time of the mosquito repellent liquid becomes longer with the increase of the proportion of trans-menthodiol, and when the effective component of the mosquito repellent liquid is pure trans, an optimal effect is reached, and the average effective repellent time reaches 6.13 hours.

[0021] Therefore, we further configure different contents of (1R)-(-)-trans-menthodiol mosquito repellent liquid, and the specific preparation method is as follows: (1R)-(-)-trans-menthodiol, double-dealcohol and water are mixed, and the mosquito repellent liquid required can be obtained after uniform mixing.

[0022] The test results show that the 8% content of (1R)-(-)-trans-menthodiol mosquito repellent liquid reaches the best balance between irritability, effective repellent time and production cost, and the irritability is significantly enhanced when the concentration is too high. Therefore, we select 8% as the reference content, and adjust the cis-trans ratio of (1R)-(-)-trans-menthodiol and (1R)-(+)-cis-menthodiol to evaluate the mosquito repellent performance of the formula, and the specific preparation method is as follows: (1R)-(-)-trans-menthodiol, (1R)-(+)-cis-menthodiol, double-dealcohol and water are mixed, and the mosquito repellent liquid required can be obtained after uniform mixing.

[0023] Further, the total content of (1R)-(-)-trans-menthodiol and (1R)-(+)-cis-menthodiol is preferably 6%-20% in the present application.

[0024] To further improve the mosquito repellent effect, the present application preferably further comprises lemon eucalyptus essential oil as a synergistic component; the specific preparation method is as follows: (1R)-(-)-trans-menthodiol, (1R)-(+)-cis-menthodiol, lemon eucalyptus essential oil, double-dealcohol and water are mixed, and the mosquito repellent liquid required can be obtained after uniform mixing.

[0025] Further, the mass ratio of the total mass of trans-menthodiol and cis-menthodiol to the mass of lemon eucalyptus essential oil is preferably 8:(1-5) in the present application.

[0026] Compared with the traditional mosquito repellent liquid mainly containing racemic cis-menthodiol, the high-efficiency mosquito repellent liquid provided by the application significantly prolongs the effective repellent time of the mosquito repellent liquid by taking (1R)-(-)-trans-menthodiol with a specific configuration as the main active ingredient (the main active ingredient refers to the component with the highest proportion in all components of the high-efficiency mosquito repellent liquid and playing a decisive role in the mosquito repellent effect) and taking (1R)-(+)-cis-menthodiol as the secondary active ingredient. In addition, by increasing the proportion of the trans-menthodiol with the specific configuration, the effective mosquito repellent time of the mosquito repellent liquid is significantly improved at the same concentration, and there is no toxic side effect. On this basis, a small amount of lemon eucalyptus essential oil is added as a synergistic component, which can further synergistically improve the continuous mosquito repellent performance, and the whole formula has no toxic side effect and high safety.

[0027] In order to make the above-mentioned purposes, characteristics and advantages of the application more obvious and easy to understand, the specific embodiments of the application are described in detail below.

[0028] Example 1: Synthesis of (1R)-(+)-cis-menthodiol and (1R)-(-)-trans-menthodiol S1: In a 50 mL single-neck flask, add magnetic sonicator and 3.8 mL of deionized water, slowly drop 9.5 mg of sulfuric acid under stirring, and after slight cooling, add 3 g of R-citronellal (19.4 mmol) to the above dilute sulfuric acid, start heating and keep at 50℃ for 7 h, after GC detection, add 5 mL of saturated sodium bicarbonate aqueous solution, separate the liquid, and then extract the aqueous phase with 50 mL*2 ethyl acetate, dry the combined organic phase with anhydrous sodium sulfate, and then rotary evaporate to obtain 800 mg of white crystal (1R)-(+)-cis-menthodiol; 1 H NMR (400 MHz, CDCl3) δ 4.34 (s, 1H), 2.85 (s, 1H), 2.54 (s, 1H),1.77-1.71 (m, 3H), 1.64-1.61(m, 2H), 1.30 (s, 3H), 1.16 (s, 3H), 1.12-1.09(m, 1H), 1.03-0.96 (t, 1H), 0.86-0.85 (m, 1H), 0.82 (d, 3H). 13 C NMR (100 MHz,CDCl3): δ 72.29, 67.08, 47.29, 41.48, 33.82, 27.88, 27.86, 24.60, 21.18,19.20;[α] D 20 +5.89 (c 0.5, CH2Cl2); S2: The filtrate from the previous step was concentrated and purified by column chromatography to obtain 510 mg of white solid (1R)-(-)-trans-menthol; 1 H NMR (400 MHz, CDCl3) δ 3.98 (br.s, 1H), 3.73 (br.s, 1H), 3.68 (td,1H), 1.89-1.84 (m, 1H), 1.64-1.58(m, 2H), 1.36-1.28(m, 2H), 1.15 (s, 6H), 1.01-0.96 (m, 2H), 0.93-0.82 (m, 4H). 13 C NMR (100 MHz, CDCl3): δ 74.05,71.89, 52.38, 43.57, 33.51, 30.34, 29.04, 26.06, 22.66, 20.96; [α] D 20 -8.77 (c0.5, CH2Cl2).

[0029] Example 2: Synthesis of (1S)-(-)-cis-menthol and (1S)-(+)-trans-menthol S1: Add a magnetic flask and 30 mL of deionized water to a 100 mL single-necked flask. While stirring, slowly add 66 mg of sulfuric acid. After slightly cooling, add 21 g of S-citronellal to the above dilute sulfuric acid. C2 (136 mmol), heating was started and maintained at 50℃ for 7 h. After GC analysis, 5 mL of saturated sodium bicarbonate aqueous solution was added. The aqueous phase was extracted with 50 mL of ethyl acetate twice. The organic phases were combined, dried over anhydrous sodium sulfate, and evaporated to dryness. 50 mL of n-hexane was added to the crude product, and the mixture was frozen at -20℃ for 24 h. The solid was filtered to obtain 7.1 g. (1S)-(-)-cis-menthol; 1 H NMR (400 MHz, CDCl3) δ 4.34 (s, 1H), 3.13 (br.s, 1H), 2.85 (br.s,1H), 1.77-1.70 (m, 3H), 1.66-1.60(m, 2H), 1.29 (s, 3H), 1.15 (s, 3H), 1.11-1.07 (m, 1H), 1.02-0.96 (t, 1H), 0.88-0.84 (m, 1H), 0.81 (d, 3H). 13C NMR (100MHz, CDCl3): δ 73.29, 68.06, 48.26, 42.49, 34.84, 28.90, 28.82, 25.60, 22.21,20.25; [α] D 20 -14.63 (c 0.5, CH2Cl2).

[0030] S2: The filtrate from the previous step was concentrated and purified by column chromatography to obtain 4.6 g of white solid (1S)-(+)-trans-menthol; 1 H NMR (400 MHz, CDCl3) δ 3.68 (td, 1H), 1.86 (d, 1H), 1.62-1.56(m,2H), 1.34-1.29(m, 2H), 1.16 (s, 6H), 0.99-0.94 (m, 1H), 0.92-0.82 (m, 5H). 13 CNMR (100 MHz, CDCl3): δ 75.09, 72.92, 53.42, 44.62, 34.54, 31.36, 30.11,27.10, 23.71, 21.99; [α] D 20 +14.29 (c 0.5, CH2Cl2).

[0031] Example 3: Synthesis of (±)-cis-menthol and (±)-trans-menthol S1: Add a magnetic flask and 159 mL of deionized water to a 250 mL single-necked flask. While stirring, slowly add 0.39 g of sulfuric acid. After slightly cooling, add 125 g of (±)-citronellol to the above dilute sulfuric acid. C1 0.81 mol), start heating, maintain at 50℃ for 7 h, after GC detection, add 20 mL saturated sodium bicarbonate aqueous solution, after separation, the aqueous phase is extracted with 100 mL * 2 ethyl acetate, the organic phases are combined, dried over anhydrous sodium sulfate, after rotary evaporation, 200 mL n-hexane is added to the crude product, and it is frozen in a -20℃ refrigerator for 24 h. The solid is filtered to give 47.4 g (±)-cis-menthol; 1H NMR (400 MHz, CDCl3) δ 4.34 (s, 1H), 1.77-1.71 (m, 3H), 1.66-1.60(m, 2H), 1.29 (s, 3H), 1.16 (s, 3H), 1.12-1.08 (m, 1H), 1.02-0.96 (t, 1H),0.88-0.85 (m, 1H), 0.82 (d, 3H). 13 C NMR (100 MHz, CDCl3): δ 73.31, 68.09,48.29, 42.50, 34.85, 28.89, 28.88, 25.62, 22.21, 20.24; S2: The filtrate of the previous step was concentrated and purified by column chromatography to obtain 26.7 g of white solid (±)-trans-mintol; 1 H NMR (400 MHz, CDCl3) δ 3.68 (td, 1H), 1.89 (d, 1H), 1.62-1.58(m,2H), 1.36-1.31(m, 2H), 1.16 (s, 6H), 0.99-0.93 (m, 1H), 0.93-0.82 (m, 5H). 13 CNMR (100 MHz, CDCl3): δ 74.06, 71.89, 52.39, 43.59, 33.51, 30.33, 29.08,26.07, 22.68, 20.96。

[0032] Example 4:10 Preparation of mosquito repellent containing commercially available mintol (cis: trans = 3:2) Take commercially available mintol 10.0 g, double-dealcohol 20.0 g, and add water to make up to 100.0 g, and mix evenly to obtain.

[0033] Example 5:10 Preparation of mosquito repellent containing S-type mintol (cis: trans = 3:2) Take (1S)-(-)-cis-mintol 6.0 g, (1S)-(+)-trans-mintol 4.0 g, double-dealcohol 20.0 g, and add water to make up to 100.0 g, and mix evenly to obtain.

[0034] Example 6:10 Preparation of mosquito repellent containing R-type mintol (cis: trans = 3:2) Take (1R)-(+)-cis-mintol 6.0 g, (1R)-(-)-trans-mintol 4.0 g, double-dealcohol 20.0 g, add water to 100.0 g, mix well to get.

[0035] Example 7:10 Preparation of mosquito repellent liquid of racemic mintol (cis: trans = 3:2) Take (1R)-(+)-cis-mintol 6.0 g, (1R)-(-)-trans-mintol 4.0 g, double-dealcohol 20.0 g, add water to 100.0 g, mix well to get.

[0036] Example 8: Preparation of 10% (1R)-(+)-cis-mintol mosquito repellent liquid Take (1R)-(+)-cis-mintol 10.0 g, double-dealcohol 20.0 g, add water to 100.0 g, mix well to get.

[0037] Example 9: Preparation of 10% (1R)-(+)-cis-mintol: (1R)-(-)-trans-mintol = 3:1 mosquito repellent liquid Take (1R)-(+)-cis-mintol 7.5 g, (1R)-(-)-trans-mintol 2.5 g, double-dealcohol 20.0 g, add water to 100.0 g, mix well to get.

[0038] Example 10: Preparation of 10% (1R)-(+)-cis-mintol: (1R)-(-)-trans-mintol = 1:1 mosquito repellent liquid Take (1R)-(+)-cis-mintol 5.0 g, (1R)-(-)-trans-mintol 5.0 g, double-dealcohol 20.0 g, add water to 100.0 g, mix well to get.

[0039] Example 11: Preparation of 10% (1R)-(+)-cis-mintol: (1R)-(-)-trans-mintol = 2:3 mosquito repellent liquid Take (1R)-(+)-cis-mintol 4.0 g, (1R)-(-)-trans-mintol 6.0 g, double-dealcohol 20.0 g, add water to 100.0 g, mix well to get.

[0040] Example 12: Preparation of 10% (1R)-(+)-cis-mintol: (1R)-(-)-trans-mintol = 1:3 mosquito repellent liquid Take 2.5g of (1R)-(+)-cis-menthol, 7.5g of (1R)-(-)-trans-menthol, and 20.0g of diethanolamine, then add water to make up to 100.0g and mix well.

[0041] Example 13: Preparation of 10% (1R)-(-)-trans-Montanediol Mosquito Repellent Take 10.0g of (1R)-(-)-trans-menthol and 20.0g of diethanol, then add water to make up to 100.0g, and mix well to obtain the final product.

[0042] Example 14: Preparation of 6% (1R)-(-)-trans-Montanediol Mosquito Repellent Take 6.0g of (1R)-(-)-trans-menthol and 20.0g of diethanol, add water to make up to 100.0g, and mix well.

[0043] Example 15: Preparation of 8% (1R)-(-)-trans-Montanediol Mosquito Repellent Take 8.0g of (1R)-(-)-trans-menthol and 20.0g of diethanol, add water to make up to 100.0g, and mix well.

[0044] Example 16: Preparation of 12% (1R)-(-)-trans-Montanediol Mosquito Repellent Take 12.0g of (1R)-(-)-trans-menthol and 20.0g of diethanol, then add water to make up to 100.0g, and mix well to obtain the final product.

[0045] Example 17: Preparation of 20% (1R)-(-)-trans-Montanediol Mosquito Repellent Take 20.0g of (1R)-(-)-trans-menthol and 20.0g of diethanol, add water to make up to 100.0g, and mix well to obtain the final product.

[0046] Example 18: Preparation of 8% (1R)-(-)-trans-Montanediol + 1% Lemon Eucalyptus Oil Mosquito Repellent Take 8.0g of (1R)-(-)-trans-menthol, 1.0g of lemon eucalyptus oil, and 20.0g of diethanolamine, then add water to make up to 100.0g and mix well.

[0047] Example 19: Preparation of 8% (1R)-(-)-trans-Montanediol + 3% Lemon Eucalyptus Oil Mosquito Repellent Take 8.0g of (1R)-(-)-trans-menthol, 3.0g of lemon eucalyptus oil, and 20.0g of diethanolamine, then add water to make up to 100.0g and mix well.

[0048] Example 20: Preparation of 8% (1R)-(-)-trans-Montanediol + 5% Lemon Eucalyptus Oil Mosquito Repellent Take 8.0g of (1R)-(-)-trans-menthol, 5.0g of lemon eucalyptus oil, and 20.0g of diethanolamine, then add water to make up to 100.0g and mix well.

[0049] The testing method used in this invention is as follows: 1. Mosquito repellent effect test (1) Test insect species and test subjects: sensitive Aedes albopictus mosquitoes, female adult mosquitoes that have not fed on blood for 3-5 days after emergence; 300 test insects are placed in the mosquito cage, and the test subject's back of hand is exposed with 40mm×40mm of skin exposed, while the rest of the hand is tightly covered. The hand is placed in the mosquito cage for 2 minutes and closely observed. When a mosquito is found to have landed, the arm is shaken to drive it away before its mouthparts penetrate the skin, and this is recorded as 1 test insect landing. If more than 30 test insects land, the test subject and test insects are considered to have qualified attack power, and this person and this cage of mosquitoes can be used for repellency tests; (2) Repelling test: Select about 6 test subjects with qualified aggression ability (half male and half female, and they should not drink alcohol, tea or coffee before and during the test, and should not use products containing fragrances). Draw a 50mm×50mm skin area on the back of each of their hands, and press 1.5μL / cm on one hand. 2 Apply the appropriate amount of mosquito repellent evenly, exposing 40mm x 40mm of skin, while completely covering the rest. Use one hand as a blank control. Two hours after application, place the hand into a mosquito cage with acceptable attack power for 2 minutes, observing whether any mosquitoes approach to stop and feed. Repeat the test every hour thereafter. If even one mosquito approaches to feed, the repellent is considered a failure. Record the effective protection time (in hours). For each test, the control hand should be used first. Tests with insects of acceptable attack power can continue; those with unacceptable attack power must be replaced with suitable insects. (3) The rating criteria for efficacy indicators are shown in the table below. 2. Test Results As can be seen from Table 2, R-type menthol has the best mosquito repellent effect. It is predicted that (1R)-(+)-cis-menthol and (1R)-(-)-trans-menthol are the two configurations with better effects, but further comparison of the effects of these two configurations is needed. Therefore, the efficacy of mosquito repellents with different cis-trans ratios was screened.

[0050] As can be seen from Table 3, at the same concentration, the effective mosquito repellent time of the mosquito repellent increases with the increase of the proportion of trans-menthol. The pure trans-menthol reaches the best efficacy. Therefore, we use (1R)-(-)-trans-menthol to screen for the optimal content.

[0051] As can be seen from Table 4, under the premise of meeting the toxicity requirements, the effective repellency time of the 8% concentration mosquito repellent is relatively ideal. Moreover, the low concentration can reduce the consumption of raw materials and production costs of the mosquito repellent. Therefore, we tried adding lemon eucalyptus essential oil at the 8% concentration to improve the mosquito repellency effect.

[0052] As shown in Table 5, the repellency time was significantly improved after adding a small amount of lemon eucalyptus oil to 8% (1R)-(-)-trans-montanediol, indicating that the addition of lemon eucalyptus oil has a synergistic effect and can further increase the duration of mosquito repellency. However, the amount of oil added should not be too much, as increasing the content by 5% can cause mild irritation to rabbit eyes. Based on the above-described ideal embodiments of the present invention, and through the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A highly effective mosquito repellent liquid, characterized in that, Trans-menthol is the main active ingredient, and lemon eucalyptus oil is the synergistic ingredient.

2. The high-efficiency mosquito repellent liquid according to claim 1, characterized in that, It also includes a secondary active ingredient, which is cis-menthol.

3. The high-efficiency mosquito repellent liquid according to claim 2, characterized in that, The mass ratio of trans-menthol to cis-menthol is 3:(0-2), and its average effective repellency time is not less than 5.74 hours.

4. The high-efficiency mosquito repellent liquid according to claim 2, characterized in that, The mass ratio of trans-menthol to cis-menthol is 3:(0-1), and its average effective repellency time is not less than 5.88 hours.

5. The high-efficiency mosquito repellent liquid according to claim 2, characterized in that, The total content of trans-menthol and cis-menthol is 6%-20%.

6. The high-efficiency mosquito repellent liquid according to claim 2, characterized in that, The total mass ratio of trans-menthol and cis-menthol to lemon eucalyptus oil is 8:(1-5).

7. A method for preparing a highly effective mosquito repellent liquid as described in any one of claims 1-6, characterized in that, Includes the following steps: S1: Using citronellol with a single configuration as a raw material, a mixture of menthol and glycol is obtained under the catalysis of acid. S2: Cis-Montanediol is obtained by recrystallization; S3: Concentrate the filtrate and then obtain trans-methylbenzyl glycol by column chromatography; S4: Mix cis-menthol and trans-menthol and add lemon eucalyptus oil to obtain a mosquito repellent.

8. The method for preparing the high-efficiency mosquito repellent liquid according to claim 7, characterized in that, The cis-menthol is selected from at least one of (1R)-(+)-cis-menthol, (1S)-(-)-cis-menthol, and (±)-cis-menthol.

9. The method for preparing the high-efficiency mosquito repellent liquid according to claim 7, characterized in that, The trans-menthol is selected from at least one of (1R)-(-)-trans-menthol, (1S)-(+)-trans-menthol, and (±)-trans-menthol.

10. The method for preparing the high-efficiency mosquito repellent liquid according to claim 7, characterized in that, The citronellal is selected from at least one of S-citronellal, R-citronellal and (±)-citronellal.

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