Comparison Of Different Extraction Methods Of Peach Leaf On Insecticidal And Repellent Activity Against Mosquito

Peach(Amygdalu spersica L.) leaves have already used as pesticide and anti-itching drugs long before, first documented in Compendium of Materia Medica(Bencao Gangmu), a classical herbal medicine book written by Li Shizhen in Ming dynasty. To further investigate its mosquito-insecticidal activity and provide scientific basis for utilizing wasted peach leaves as mosquito controlling agents, the peach leaves were extracted by water extraction by alcohol precipitation, ethanol extraction, petroleum ether extraction(PE) and steam distillation(SD).The mosquito-larvacidal activity of peach leaves extractives by different extract methods was investigated. The larvacidal activity of all extracts against Culex pipiens pallens were studied. And fumigation activity against Culex pipiens pallens and repellant activity against Aedes albopictus were also assayed. Study results are as follows:1. Essential oils of peach leaves through stream distillation method have the highest mosquito larvicidal activity.Extraction methods have a strong effect on mosquito larvicidal activity, with SD extraction method evaluated as the best method(LC50=27.73 mg·L-1). Water extracts by alcohol precipitation at 20 g·L-1 concentration have no mosquito larvicidal activity. Ethanol extracts of 5 g·L-1 concentration have some mosquito larvicidal activity, with insecticidal rate reaching 80%. The larvacide bioassay order of different extraction methods are as follows: water extraction by alcohol precipitation < ethanol extraction < petroleum ether extraction < water vapor distillation.2. SD essential oil of peach leaves have great potency to be mosquito repellent.Repellent capacity of 40 % SD oil of peach leaves reach 90.4% against Aedes albopictus after 4 h treatment. Therefore, it has good potential to be repellant agent for Aedes albopictus.3. SD peach leaves oil can be used in the control of Culex pipiens pallens.Larvacidal and fugmitant avtivity assay demonstrated that SD essential oil of peach leaves have great performance against Culex pipiens pallens, with the LC50 value of 27.73 mg·L-1(PE 71.98 mg·L-1 oil) against 3 instar larvae and 1.03 μL·L-1 against female adults, higher than the 2.31 μL·L-1 of PE oil, implying its potent utilization as insecticide against Culex pipiens pallens.4. SD and PE essential oils of peach leaves were analyzed by GC-MS, with ten ingredients each. Pentacosane and phytol were their shared compounds, and each relative content is above 8%. The major compounds of PE essential oils were Sclareol(or Manool)(38.72%), organic ester(13.92%), and allylic hydrogen(16.19%). While the major compounds of SD essential oils were benzoid(66.98%), allylic hydrogen(10.28%) and phytol （10.02%）...