The Study Of The Efficacy And Mechanism Of Carvacrol And Eugenol Against Sarcoptes Scabiei

Scabies is an infectious skin disease caused by Sarcoptes scabiei,which can cause intense itch,secondary infection and death.With the excessive use of chemical synthetic miticides,the problems of drug resistance and environmental pollution have gradually emerged.As existing drugs have short half-life and lack ovicidal activity,there is an urgent need to develop new miticides to solve these problems.Due to low toxicity,easy degradation and resistance to drug resistance,essential oils and their components have the potential to become new miticides.Our previous study has shown that essential oils of clove,palmarosa,lemongrass,tea tree and lavender are effective against the motile stages of Sarcoptes mites.The major components of these essential oils are eugenol,geraniol,citral,terpinene-4-ol and linalool,respectively.However,to date there is no report showed the ovicidal effect of the six monoterpenes（carvacrol,eugenol,geraniol,citral,terpinen-4-ol and linalool）against S.scabiei.Therefore,in this study the ovicidal and miticidal activity of six monoterpenes were tested and effective monoterpenes were screened out.TMT labeling quantitative proteomics technology was applied to study the mechanism of action of effective monoterpenes.This study mainly includes the following three parts:The miticidal activity of 6 essential oil monoterpenes（5%,1%and 0.5%）was evaluated by contact bioassay in vitro.The result showed that the LT₅₀values of carvacrol,eugenol,geraniol,citral,terpinen-4-ol and linalool at concentration of 0.5%were 6.7 min,33.8 min,48.1 min,6.1 h,22.3 h and 39.9h,respectively.All six essential oil monoterpenes revealed miticidal activity,of which carvacrol,eugenol and geraniol were the most effective against motile stages of S.scabiei.The ovicidal activity of 6 monoterpenes of 5%was evaluated by filter paper immersion.The result showed that carvacrol,eugenol,geraniol,citral,terpinen-4-ol and linalool all resulted in more than 90%eggs mortality.All six essential oil monoterpenes presented ovicidal activity after long time reaction.The ovicidal activity of 6 monoterpenes（5%,2.5%and 1%）were tested with a optimized filter paper immersion method.The result showed that the EC₅₀ value of carvacrol,eugenol,geraniol,citral,terpinen-4-ol and linalool was 0.5%,0.9%,2%,4.8%,5.1%and 9.8%,respectively.All six essential oil monoterpenes demonstrated ovicidal activity,and carvacrol and eugenol were the most effective against S.scabiei eggs.The eggs treated with 6 monoterpenes of 1%were photographed to observe the internal development at an interval of 12hours by microphotography.The result showed that carvacrol and eugenol were able to stop the development of eggs in 0～24 hours,indicating that the two essential oil monoterpenes had high ovicidal effect against early stage eggs.To clarify the miticidal mechanism of carvacrol and eugenol,TMT labeling quantitative proteomics was employed to obtain the differentially expressed proteins of Sarcoptes mites treated with carvacrol and eugenol compared with negative control group,and bioinformatics analysis was performed on the differentially expressed proteins.Finally,PRM technology was used to verify the differentially expressed proteins.In the Carvacrol/Control group,235differentially expressed proteins were identified（113 up-regulated,122down-regulated）.Analysis of GO function and KEGG pathway revealed that the miticidal mechanism may be related to oxidative phosphorylation,cholinergic synaptic pathway,drug metabolism pathway and so on.In the Eugenol/Control group,103 differentially expressed proteins were identified（43 up-regulated,60down-regulated）.Analysis of GO function and KEGG pathway found that the miticidal mechanism may be related to oxidative phosphorylation,ribosome pathways and so on.In the two comparison groups,there were 15 differentially expressed proteins,such as elongation factor 1-alpha,carboxylesterase and so on.Four differentially expressed proteins,including palmitoyl-protein hydrolase1,pyrroline-5-carboxylate reductase,heat shock protein 70,and cathepsin B,were identified by PRM,and the result was consistent with TMT analysis.In this study,carvacrol and eugenol have high miticidal and ovicidal effects.The miticidal mechanism of the two monoterpenes may be related to proteins in pathways such as oxidative phosphorylation,cholinergic synapses,drug metabolism and ribosomes.These research conclusions will provide theoretical support for the development and utilization of new botanical miticides.