| Eucalyptus oil is a kind of aromatic oil that is derived from the leaves of Cinnamomum longepaniculatum by steam distilation. In recent years, it has been demonstrated to possess many biological activities, such as antimicrobial, antifungal, anticancer, anti-imflammatory and antioxidation. Moreover, it also can act as an insect repellent to provide protection against parasites, such as mosquito bites, scabies mites, and so on.1,8-cineole is a common compound found in eucalyptus oil, and the content of the 1,8-cineoIe is about 58.55%. To solve the problems of drug toxicity and drug resistance with chemical drugs, this study conducted to determine the acaricidal activites of 1,8-cineole against S. scabiei var.cuniculi and depict the acaricidal mechanism though measuring the enzyme activities for the purpose of developing new acaricidal targets.1 Study on the acaricidal activity of 1,8-cineole in vitro:Measured 1,8-cineole were used to kill way to determine its acaricidal activity of S.scabiei var. cuniculi larvae in vitro. The results indicated that the 1,8-cineole the the lethal concentration of 50%(LC50) value (95% confidence limit (CL)) of 1,8-cineole were 2.77 mg/mL. When the concentrations of 1,8-cineole were 9.2mg/mL,4.6mg/mL,2.3mg/mL, the lethal time of 50%(LT50) value (95%CL) were 3.606h,7.416h,11.296h. Conclusion:The results showed that 1,8-cineole has effective resistance to rabbit scabies mites, and the concentration is higher, the effective resistance to rabbit scabies mites is better.2 The effects on the morphology of S.scabiei var. cuniculi larvae with 1,8-cineole: Larval mites were placed in small polystyrene plates with 40 mites per plate. The 1,8-cineole was diluted with liquid paraffin to 2.3 mg/mL,4.6 mg/mL,9.20 mg/mL. Posttreatment was performed after 12h. The clinical symptoms of mites were observed by optical microscope, and the mites were fixed by precooling of glutaraldehyde and made into ultra-thin slicings to observe the influence on body ultrastructure of mites. After treatment, the mite manifested some clinical symptoms. At the beginning, the mite kept moving frequently; the mite revolved quickly and repeatedly around its own axis and had excitement tics of forefoot. The mite tried to escape from the plate after a while but moved more slowly and spawned sharply. Finally, the mite stayed, and the body shrank to death. Under transmission electron microscope, the mites in the control group had regular skin stripes and inact body cavity cells, While in the experimental groups, the skin prickle cells were vacuolized; the dermatoglyph layer was irregular, and the mitochondrias were vacuolized; the cellular contents and nuclear chromatin were dissolved.3 The influence of enzyme activity in the protective enzyme, detoxifying enzyme, neurotransmitter enzyme, neural effector enzyme:With concentration of 9.2 mg/mL, 4.6 mg/mL,2.3 mg/mL of 1,8-cineole and liquid paraffin processing rabbit scabies mites respectively in 4 h,8 h and 12 h proenzyme extract preparation of worm body, and then assaying the activity of enzymes including superoxide dismutase (SOD), glutathione-s-transferases (GSTs), monoamine oxidase (MAO), Ca2+-ATPase, acetylcholinesterase (AChE) and nitric oxide synthase (NOS).The result showed that within 12 h, the enzyme of SOD of the rabbit scabies mites with different concentrations of 1,8-cineole treatment in the experimental groups was increased when compared with the control group. And the increasing level was from 6.11% to 43.83%. The result showed that 1,8-cineole could increase the levels of free radicals in the body, and then induce the increase of the enzyme of SOD activity.The result showed that within 12 h, different concentrations of 1,8-cineole treatment with rabbit scabies mites, the enzyme of GSTs was increased when compared with the control group. And the increasing level was from 41.10% to 684.02%. The result showed that 1,8-cineole acted as an exogenous toxicant. When 1,8-cineole was into the insect body, it could activate the body’s defense system, and reduce the toxicity of 1,8-cineole.The result showed that within 12 h, the enzyme of MAO of the rabbit scabies mites with different concentrations of 1,8-cineole treatment in the experimental groups was increased when compared with the control group. And the increasing level was from 17.99% to 244.73%. The increased enzyme of MAO could cause the neurotransmitter of insect body accelerate and then lead to the mites excited and die. From 0 to 8 h, the enzyme of Ca2+-ATPase of rabbit scabies mites in the experimental groups was below to that in the control group, while 12 h, the enzyme in the experimental groups was higher than that in the control group. The result showed that in the early stage of the drug, the insect body was so excited that it needed to spend more energy; while in the late stage of the drug, the mites were dead and the enzyme of Ca2+-ATPase was decreased.The result showed that within 12 h, different concentrations of 1,8-cineole treatment with rabbit scabies mites, the enzyme of AChE was decreased when compared with the control group, and the higher the concentration of 1,8-cineole was, the lower the enzyme of AChE was. The concentration of 9.2 mg/mL, the AChE activity inhibition rate up to 65.52%; the concentration of 2.3 mg/mL, the AChE activity inhibition rate as low as 5.56%. The result showed that 1,8-cineole could inhibit the enzyme of AChE to improve the level of ACh, and cause the insect body superexcited and die. The NOS activity of larval mites treated with 9.2 mg/mL 1,8-cineole was significantly lower than that of the control group at all test points throughout the experiment. While the activity of larval mites treated with 4.6 and 2.3 mg/mL 1,8-cineole increased significantly as compared with the control group. The result showed that high concentration of 1,8-cineole would inhibit the NOS activity of larval mites, while the low concentration of 1,8-cineole would increase the NOS activity.In conclusion,1,8-cineole might change the activity of NOS and Ca2+-ATPase, resulting in the nervous system abnormalities of insect body and death. |
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