| Plant essential oils, volatile and highly fragrant liquids, are important secondary metabolites present in different tissues of the plant. Essential oils are used in the field of medicine, healthcare, and fruit industry (keeping the fruit fresh). Several studies have shown that these oils possess different kinds of bioactivities (pesticidal, funficidal and antiviral activities and may own synergistic effects. Because of the strong volatile nature, these oils may be suitable for controlling house and sanitary insect pests. Based on that, this study was aimed at investigating the interaction of constituents of essential oil and the synergistic effects on pyrethroids and making preparations. The results are as follows:1. Using Aedes albopictus as the target insect,37plant essential oils were screened for the repellent action and fumigation action.(1) sassafras oil, citriodora oil, Litsea cubeba oil, Citrus aurantium oil, L., Five times of orange oil and dai-dai flower oil showed comparable strong repellent effects than Longlife floral water after2-4h treatment, among which citrus aurantium oil and litsea cubeba oil showed50%repellent ratio after4-6h treatment worthy further study;(2) Though essential oils all showed fumigation action to adult aedes albopictus, different cultivars had different effects. Wintergreen oil, lemon grass oil and myristica oil, had LC50level lower than5μL·L-1after6h treatment and had LC50level of2.2μL·L-1,3.8μL·L-1and4.9μL·L-1, respectively. Ten oils showed some fumigation activity with less than5-10μL/L-1LC50level.(3) Tea tree oil, myristica oil, valerian oil and Ocimum gratissimum oil showed unexpectedly attractant effect and need to be considered for future research.2. For the screening of solvent and emulsifier,10EC wintergreen oil and10EC lemon grass oil were selected fitting the commodity commands:(1) recipe of10EC wintergreen oil: wintergreen oil10%, emulsifier02045%and95%ethanol for the rest;(2)10EC lemon grass oil recipe:lemon grass oil10%, exclusive used emulsifier N1:0204(6:4)5%and ethyl acetate:95%ethanol (4:6) for the rest. Fumigation active tests showed that10EC natural wintergreen oil and10EC lemongrass oil’s LC50of fumigation active against Aedes albopictus were0.4951μL·L-1and0.2384μL·L-1respectively; under the dose of LC95, LT50of10EC natural wintergreen oil and10EC lemongrass oil were13.85min and10.06min respectively. The two kinds of essential oils emulsifiable solution (EC) were environment-friendly, and had high insecticidal effects, needed further industrialization development.3. In terms of mosquito coils synergistic agent, S2, had been banned from the market. Plant essential oil solvents were screened on the basis of mosquito-repellent incense synergist as synergist formula. The results show that four kinds of solvent, butyl acetate, ethyl formate and diethyl carbonate etc., had good solubility in the deodorization of kerosene oil and could be used as a solvent in the preparation of plant essential oil synergist. To study the synergistic effect of single compound and mixtures using sassafras oil, anise leaf oil, natural wintergreen oil and lemon grass oil, we screened11kinds of plant essential oil synergist effects for allyl chrysanthemum ester, the11kinds of synergistic agent recipe were40.0%～80.0%plant essential oil+13.5%～53.5%solvent+6.5%emulsifier OP-10. Sealed cylinder method was used to test11kinds of synergist mosquito-repellent incense for fumigation activity against Culex pipiens. The results showed that KT50of11kinds of mosquito-repellent incense samples were less than2min, reaching the national A-level standard; The SRs of five mosquito-repellent incenses (14#、16#、25#、26#、28#) were1.33,1.34,1.29,1.36and1.30respectively, showing good synergistic effects comparing with control synergist S2’s SR (1.28).4. Based on the liquid formula of the commercially available "lanju" aerosol, we studied the plant essential oil of aerosol synergist by using5.8m3cottage method and the28m3simulated field efficacy method. The wintergreen oil and β-pinene screened from the selected six plant essential oil showed good synergistic activity, KT50of the aerosol by mixing these two compounds was reduced by2.3927min and1.3819min respectively compared with the sample by adding chemical synergistic agent; using wintergreen oil as the main synergistic ingredient and YW, Y001, Y002, and YN as surfactant or penetrating agent, we developed three synergistic agent formulas, S-101, S-102and S-103. Activity test through5.8m3cottage method showed that S-102had the best synergistic effect reducing the level of KT50(chemical synergistic agent S-1) by4.1875min with SR1.38. S-103and S-101also showed strong synergistic actions with SRs1.23and1.16respectively. According to the test results of28m3simulated field method and the sanitary insecticide efficacy evaluation standard, aerosol B and C reached A-level standard, and aerosol A reached B-level standard.5. GC-MS analysis of Listsea pungent and L. cubeba oils showed that:(1)11compounds of L. pungent fruit oil comprised92.7%of the total oil, with1,8-cineole (43.6%) and limonene (27.2%) being the main constituents;(2) Six components from L. cubeba oil comprised89.9%of the total with gamma-Terpinene (43.6%) and limonene (27.2%) being the main constituents;(3) Bioassay showed that the LD50values of L. pungent fruit oil and L. cubeba oil against third instar larvae of cabbage loopers were87.1μ.g/larva and112.4μg/larva respectively;(4) Though the single compounds or the mixture of the main constituents of L. pungent fruit oil, L. cubeba oil,1,8-cineole, limonene, gamma-Terpinene and limonene, didn’t show any contact activity, their synergistic effects were obvious. Our results showed that all constituents whether active or inactive, were required for the total activity of the oil.6. Comparing the different extraction methods (steam distillation method versus supercritical CO2extraction) using Qinling Mountains aromatic plant, L. pungent fruit oil as material, we got the following results:(1) The efficiency of supercritical CO2extraction was far more superior than steam distillation method;(2) After1g was loaded, the best craft for supercritical CO2extraction was:static extraction for10min, holding pressure at4000psi at55℃and40mL CO2. The production under this optimal condition was7.85%;(3) Pesticidal assay against housefly showed reversed results for these two methods and the LC50of steam distillation method and supercritical CO2extraction were170.54μL/L and566.79μL/L respectively.Studying bioactivity of essential oils is a very promising field of research, although it is also complicated, and esoteric. Many ancient books on essential oils claim that essential oils not only repel the insects but the evil too, pointing towards the magic function of essential oils. The results of our study further confirm their potential as botanical insecticides against pests, especially the hygienic insects. |
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