| Aedes albopictus Skuse and Culex pipiens quinquefasciatus Say, two species of common blood-feeding mosquitoes in China, they can transmit diseases which are seriously harmful to human health. Essential oils of plants are rich of bioactive substances and has advantages such as environmentally friendly, low toxicity, easily degradable, and little resistance to mosquitoes. It has became a research hotspot to use essential oil against mosquitoes.Six groups components of essential oils were extracted from Cinnamomum japonicum by decompressed distillation, Insecticidal activity of the essential oils against IV instars larvae and pupae of Ae. albopictus and Cx. quinquefasciatus were investigated by immersion method; Fumigation toxicity against adults of Ae. albopictus and Cx. quinquefasciatus at different concentration were carried out by airtight fumigation in conical flask; The chemical components of these essential oils were also qualitatively analyzed by gas chromatography-mass spectrometry. The results were listed as follows.The 24 h LC50 values of essential oils from Cinnamomum japonicum for the IV instar larvae of Ae. albopictus/Cx. quinquefasciatus were 75.02/84.4 μg·mL-1 and 80.17/86.62 μg·mL-1 ; The 24 h LC50 values of essential oils from group 1 to group 6 for the IV instar larvae of Ae. albopictus were 35.39/41.54,38.36/52.50,38.82/45.24, 79.49/88.82,78.24/137.13,80.24/90.36 μg·mL-1 respectively, to Cx. quinquefasciatus were 50.83/60.30,51.30/56.12,60.33/71.39,81.36/84.66,82.63/90.35,140.04/381.25 μg·mL-1 respectively. Toxic effects of group 1 to 3 better than group 4 to 6 and essential oils from Cinnamomum japonicum, toxic effects of group 4 to 6 lower than essential oils from Cinnamomum japonicum.The 24 h LC50 values of essential oils from Cinnamomum japonicum, group 1 to group 6 against adults of Ae. albopictus/Cx. quinquefasciatus by airtight fumigation in conical flask were 25.44/31.08 μg·cm-3,15.63/20.39 μg·cm-3,16.77/21.68 μg·cm-3, 18.65/25.34 μg·cm-3,29.35/30.46 μg·cm-3,41.99/42.32 μg·cm-3,33.97/45.63 μg·cm-3, And the 24 h LC50 value of group 1 was the best.Qualitative analysed chemical components of essential oils from Cinnamomum japonicum and six groups. Thirty-nine compounds were identified in essential oil of Cinnamomum japonicum, including the main component Borneol (32.51%), followed by Eucalyptol (16.91%),p-Cymene (7.75%), α.-Terpineol (5.32%),3-Cyclohexadiene (3.61%), (1R)-(+)-a-pinene (3.24%) and D-Limonene (3.03%); Group 1 and group 2 were contained seven compounds, eight compounds in group 3, and group 4, group 5, were contained five compounds; four compounds in group 6. Eucalyptol and (1R)-(+)-a-pinene were discovered at six groups. Distill for 20 minutes under the pressure of 0.090 MPa and obtain group 1 which the bioactivity against mosquitoes is the best, and it must be have related to the high level of D-Limonene, tert-Butylbenzene,3-Cyclohexadiene. Besides Borneol, Eucalyptol, α-pinene were have bioactivity against mosquitoes. P-isopropyltoluene might have synergistic effect on the bioactivity of a-pinene against mosquitoes.The result from above shows that there are large numbers of bioactive substances in the essential oil from the leaves of Cinnamomum japonicum, optimize the technology of separation the essential oil to obtain the higher purity components and select efficient insecticidal active substances, it will provide guiding fuction for the production of botanical pesticides. |
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