Eugenol And Trans-cinnamaldehyde Reduces Blood-feeding Success In Culex Pipiens Quinquefasciatus

Culex pipiens quinquefasciatus is one of the major vector-borne insects,transmitting a variety of infectious diseases such as yellow fever,malaria and dengue fever.Controlling the number of Culex pipiens quinquefasciatus is a systematic project.Because of the high application rates and intensive treatment of conventional mosquitocides in mosquito control programs,we are facing an increased risk of pesticide resistance,resurgence of pests and residues in biota.The plant-borne compounds usually exert toxicity through multiple mechanisms of action and pleiotropic actions,such as ovicidals,larvicidals,pupicidals,adulticidals,oviposition deterrents,repellents,reproduction inhibitorsand are less prone to resistance than that of single mechanisms of action.Moreover,the plant-borne compounds can be used as regulators of behavior in insect or synergist to enhance insecticidal or repellent effect of conventional insecticide to pest insect.In this paper,we developed some eco-friendly mosquitocidal agent from 12 essential oils against the Culex pipiens quinquefasciatus from Zhongshan,Guangdong,China.Based on this,we studied the mechanism of eugenol and trans-cinnamaldehyde reduces blood-feeding success in Culex pipiens quinquefasciatus.The main results and conclusions are shown as follows:μ1.The knock-down activity（24.20μL/L）of citral,trans cinnamaldehyde,camphor,terpineol,eugenol,limonene,linalool,cineole,carvone,citronellol,para-cymene and gamma-terpinene were evaluated against Culex pipiens quinquefasciatus using conical flask method.Their KT₅₀values were 40.73、13.67、8.00、7.54、6.43、7.00、5.74、4.41、3.39、13.38、4.21 and 4.92 min respectively.Base on the preliminary screening,the six most fumigant toxicity plant-borne compounds were selected,including carvone,eugenol,linalool,citronellol,terpineol and trans cinnamaldehyde,and their fumigant toxicities were determined using conical flask method at the concentration of 3μL/L.Their mortality rates were 86.7%,100%,84.4%,93.8%,100%and 100%respectively,survived 6-hour contact exposure and recorded the mortality after 24 hours.Eugenol and trans-cinnamaldehyde showed excellent fumigant toxicity with the LC₅₀values were 0.66 and 0.24μL/L respectively.2.The biting rates of blood-feeding after fumigation with eugenol and trans-cinnamaldehydel by LC₂₅treatment dosages（0.46μl/L and 0.19μl/L）were determined.The results showed that the mortality rates were 22.56%and 23.33%;the inhibition rates of bite were 89.31%and 69.34%;the inhibition rates of hatchability were 4.79%and 7.21%respectively.The oviposition rate of fumigation with eugenol and trans-cinnamaldehydel by LC₂₅treatment dosages（0.46μl/L and 0.19μl/L）after blood-feeding were determined.The results showed that the mortality rates were 21.67%and 23.33%;the inhibition rates of oviposition were 11.36%and 13.98%;the inhibition rates of hatchability were 11.86%and 13.98%,respectively.3.The repellent effects of eugenol and trans-cinnamaldehydel on Culex pipiens quinquefasciatus were determined.Their protective durations were 60 and 150 min at the concentration of 2.20μg/cm³;the attack rates were reduced by 67.25%and 63.92%,respectively,at the concentration of 0.46μl/L and 0.19μl/L.The capable of generating electrical response of Culex pipiens quinquefasciatus to eugenol and trans-cinnamaldehydel were recorded for two dosages using antenna electrophysiology（EAG）technique.The results showed that eugenol and trans-cinnamaldehydel elicited nonsignificant electroantennogram activity from Culex pipiens quinquefasciatus antennae and there was not a logistic dose–response relationship between the generating electrical response and the stimulus concentration.The enzymatic activity of mitochondrial respiratory chain complexⅠ（NADH:UQ oxidoreductase）、complexⅡ（succinate:UQ oxidoreductase）、complexⅢ（cytochrome bc₁）、complexⅣ（cytochrome c oxidase）and complexⅤ（ATP synthase）of Culex pipiens quinquefasciatus on eugenol and trans-cinnamaldehydel using conical flask method were assessed.The results showed that the enzymatic activity of NADH oxidase,succinate oxidase,NADH dehydrogenase,succinate dehydrogenase and cytochrome c reductase succinate were 106.46%,159.69%,146.38%,335.09%,197.32%and 90.73%,106.51%,119.82%,343.46%,122.20%,respectively.The effect of eugenol and trans-cinnamaldehydel by LC₂₅treatment dosages（0.459μl/L and 0.191μl/L）on ATPase,SOD and ATP in Culex pipiens quinquefasciatus using conical flask method were determined.The results showed that the inhibition rates of eugenol and trans-cinnamaldehydel on Na⁺/K⁺-ATPase and Ca²⁺-ATPase activity were35.95%and 33.22%,21.98%and 24.96%,respectively.The ATP content was increased by216.24%and 208.36%,respectively.