| Objective:In this study,the acaricidal activity of the extracts of five Chinese herbal medicines,including Radix inulae,Litsea cubeba,Agastache rugosa,Flacourtiaceae and Acorus gramineus were tested against Dermatophagoides farinae,and A.gramineus with the best acaricidal effect was selected as the follow-up research object.Isolation and identification of effective acaricidal components of A.gramineus extract,and explore its acaricidal mechanism.In order to develop a plant-derived acaricide that is non-toxic to the human body and has good acaricidal effect.Methods: The acaricidal tests were carried out on the extracts of five Chinese herbal medicines: R.Inulae,L.cubeba,A.rugosa,Flacourtiaceae and A.gramineus.The best essential oil of A.gramineus was isolated and identified.The oil was prepared by positive silica gel column under medium pressure using high-performance liquid chromatography(HPLC),and each component was collected.The acaricidal activity of different components was compared.Mass spectrometry,nuclear magnetic resonance(1H-NMR and 13C-NMR)were used to identify the components with good acaricidal effect.The acaricidal activity of active ingredients was compared with 4 plant derived acaricides and 5 chemical acaricides commonly used in the market to explore their practical application value.To study the effect of active components on gene transcriptome of D.farinae,and preliminarily explore the mechanism of acaricidal.Results:(1)The extracts of R.Inulae,L.cubeba,A.rugosa,Flacourtiaceae and A.gramineus had good killing activity to D.farinae,and the 24 h corrected mortality rate was more than 85% when the concentration was 1%.When the essential oil was diluted to 0.125%,the 24-hour corrected mortality of mites was 100%.When the oil was diluted to 0.0625%,the corrected death rate of mites reached 94.33% in 24 hours.(2)The essential oil of A.gramineus was isolated and identified,six components A-F were isolated,and the acaricidal activities of the different components were compared.It was found that the acaricidal effects of component D and component E were good.When the concentration of component D was diluted to 0.25%,all mites died,and when the concentration of component D was diluted to 0.125%,the corrected mortality of mites in 24 hours reached about 93.67%.When the concentration of component E was diluted to 0.0625%,all mites died,and when the concentration of component E was diluted to 0.03125%,the24-hour corrected death rate of mites was about 82.67%.By mass spectrometry,1H-NMR and13C-NMR analysis of components D and E,group D was identified as isoeugenol methyl ether and group E as β-asarum.β-asarum is toxic to human body,so it is not used as the object of follow-up study.(3)The acaricidal activity of isoeugenol methyl ether was compared with that of 4 plant acaricides and 5 chemical acaricides commonly used in the market.The results showed that the acaricidal activity of isoeugenol methyl ether was superior to rotenone,celangulins,matrine,avermectin,profenofos-phoxim,propargite,spirodiclofen,and pyridaben,but slightly lower than azadirachtin.(4)By using isoeugenol methyl ether to treat D.farinae,statistical analysis of differential genes and comparison between control and treatment groups showed a total of 1945 differentially expressed genes,of which 986 were up-regulated,such as sphingomyelin,hydrolase,sphingomyelin phosphodiesterase,and 959 were down-regulated,such as: Hexose transferase,cysteine type endopeptidase inhibitors,glucose ceramidase,etc.GO enrichment analysis of differential genes showed that they mainly affected ion transport,proteolysis,chitin binding,carbohydrate metabolism and serine-type endopeptidase activity of D.farinae.KEGG enrichment of differential genes showed that the main enrichment pathways were pancreatic secretion pathway,fat digestion and absorption pathway,antigen processing and presentation pathway,starch and sucrose metabolism pathway,other glycan degradation pathway,and lysosome pathway.It was found that its mechanism of acaricidal may affect the transport of potassium ions and act on the nervous system.Thirteen genes were selected from the identified differential genes,and fluorescence quantitative analysis of the m RNA expression of the treated mites was performed by RT-q PCR.The results showed that the expression levels of the above genes had significantly changed,indicating that these genes played an important role in the regulation of D.farinae.Conclusion: In this study,it was found that the rhizome extract of A.gramineus had good acaricidal activity against D.farinae.The main components were isoeugenol methyl ether andβ-asarol.Isoeugenol methyl ether has no adverse effects on human body and environment,so it can be used as a good acaricide in practice.Its effect is better than most commonly used plant and chemical acaricides on the market.Through transcriptomic analysis,it was found that its mechanism of acaricidal may affect the transport of potassium ions and act on the nervous system. |
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