Background: Mosquitoes are responsible of numerous vector-borne diseases and among these diseases is malaria which takes away lives of thousands of people, especially children of under five, particularly in Africa. To...Background: Mosquitoes are responsible of numerous vector-borne diseases and among these diseases is malaria which takes away lives of thousands of people, especially children of under five, particularly in Africa. To reduce the mortality and economic burdens of this deadly disease, synthetic insecticide has been of use to control its main vector, Anopheles gambiae. Due to adverse effects caused by these conventional products on non-target organisms and the environment, plants have been of first choice as they proved their effectiveness against mosquitoes and are said to be eco-friendly and relatively safer. Therefore, the aim of this study was to screen the phytochemicals and determine the larvicidal and adult emergence exhibitory activities of Momordica charantia and Hyptis spicigera leaves extracts against Anopheles gambiae larvae. Methods: The WHO standard protocol for larvicidal activity and IGRs was followed up and concentrations from 500 - 2000 ppm for larvicidal and 500 - 1500 ppm for IGRs were set up. Results: There was the presence of alkaloids, flavonoids, tannins, phenols, steroids, terpenoids and oils in Momordica charantia against alkaloids, taponins, tannins, phenols, steroids, terpenoids and oils in Hyptis spicigera. Methanol crude extract registered the lowest LC<sub>50</sub> value of 270.6 ppm followed by ethyl acetate and hexane fractions recorded the LC<sub>50</sub> of 742.1 and 756 ppm, respectively for larvicidal activity of Momordica charantia against LC<sub>50</sub> of 760 and 867.5 ppm for hexane fraction and methanol crude extract, respectively for Hyptis spicigera. Methanol crude extract and hexane fraction of both plants as well as the ethyl acetate fraction of M. charantia registered greater emergence inhibition with IE<sub>50</sub> values of 590.2, 842.3 and 982 ppm for methanol crude extract, hexane and ethyl acetate fractions of M. charantia, respectively against 901.7 and 873.2 for methanol crude extract and hexane fraction of H. spicigera, respectively. Conclusion: The toxicity a展开更多
Background: Anopheles gambiae is enemy number one of mankind in Africa and particularly in Cameroon due to its ability of transmitting malaria which is the deadliest disease in this part of the world. Synthetic insect...Background: Anopheles gambiae is enemy number one of mankind in Africa and particularly in Cameroon due to its ability of transmitting malaria which is the deadliest disease in this part of the world. Synthetic insecticides have been used to control malaria vectors but they have negative effects on non-target organisms and are environmentally unfriendly. Control of mosquitoes at larval stages using phytochemicals is currently the leading tool to reduce the mosquito population and so the reduction of malaria transmission rates. Therefore, the present study was to evaluate the phytochemical contents, larvicidal and adult emergence inhibition activities of Balanites aegyptiaca seed and Aristolochia albida root solvents extracts against Anopheles gambiae larvae. Methods: The World Health Organization standard protocols were followed for the different bioassays. Concentrations ranging from 500 - 2000 ppm for larvicidal and 500 - 1500 ppm for IGRs were used. Results: Both plants showed the presence of alkaloids, flavonoids, saponins, tannins, phenols, terpenoids and oils except the absence of phenols in Aristolochia albida. The larvicidal activity of Aristolochia albida extracts showed that hexane and methanol fractions were the most active killing relatively all exposed larvae with the LC<sub>50</sub> values of 420.1 and 453 ppm, respectively. The same observation was made in hexane fraction from Balanites aegyptiaca (LC<sub>50</sub> = 588 ppm). The insect growth inhibitory activity of Aristolochia albida extracts proved that hexane and methanol fractions relatively caused a 100% inhibition in the mosquito development, recording the EI<sub>50</sub> values of 482.4 and 555.6 ppm, respectively. The same trend was observed with Balanites aegyptiaca hexane fraction registering better EI<sub>50</sub> of 623.9 ppm. Conclusions: Our findings demonstrate that Balanites aegyptiaca seed and Aristolochia albida seed extracts are rich in phytochemicals capable of killing mosquito larvae and disrupting mosquito larval development.展开更多
The comprehensive knowledge that the delayed systemic and reproduction side effects can be even more deleterious than acute toxicity, has caused a shift in focus toward sublethal effects assessment on physiology and b...The comprehensive knowledge that the delayed systemic and reproduction side effects can be even more deleterious than acute toxicity, has caused a shift in focus toward sublethal effects assessment on physiology and behavior of beneficial insects. In this study, we assessed the risks posed by some insecticides with different mode of action through lethal and delayed systemic sublethal effects on the pupation, adult emergence, and repro- duction of the chrysopid Chrysoperla externa （Hagen, 1861; Neuroptera： Chrysopidae）, an important predator in pest biological control. The maximum field recommended dose （MFRD） and twice （2xMFRD） for chlorantraniliprole, tebufenozide, and pyriproxyfen were harmless to C. externa. In contrast, all the tested chitin synthesis inhibitors （CSIs） were highly detrimental to the predator, despite of their lack of acute lethal toxicity. There- fore, the safety assumed by using IGRs toward beneficial insects is not valid for chrysopids. Dose-response data showed that although all CSIs have a similar mechanism of action, the relative extent of toxicity may differ （novaluron 〉 lufenuron 〉 teflubenzuron）. For CSIs, the delayed systemic effects became obvious at adult emergence, where the predicted no observable effect dose （NOED） was 1/2 048 of the MFRD for novaluron （0.085 ng/insect）, and 1/256 of the MFRD for both lufenuron （0.25 ng/insect） and teflubenzuron （0.6 ng/insect）. Finally, this work emphasized the significance of performing toxicity risk assessments with an adequate posttreatment period to avoid underestimating the toxicities of insecticides, as the acute lethal toxicity assays may not provide accurate information regarding the long-range effects of hazardous compounds.展开更多
Allatostatins （ASTs）, a family of insect neuropeptide, can inhibit juvenile hormone （JH） biosynthesis by the corpora allata （CA） in Diploptera punctata, and therefore be regarded as potential leads for the disco...Allatostatins （ASTs）, a family of insect neuropeptide, can inhibit juvenile hormone （JH） biosynthesis by the corpora allata （CA） in Diploptera punctata, and therefore be regarded as potential leads for the discovery of new insect growth regulators （1GRs）. But several shortcomings, such as their sensitivity to peptidases and high cost, impeded their practical application in pest management. In order to discover new IGRs, one AST analog B1 possessing non-peptide group was discovered with high ability to inhibit JH biosynthesis in vitro （IC50： 0.09 μmol/L） in our previous studies. In the present work, two series of B1 analogs with different substituents on the N-terminus region were designed and synthesized. The result suggested that benzene showed better activity than other heterocycles, and the para-substitution on the benzene was beneficial for activity. Moreover, analogs with logP value over 2.0 exhibited good activity, which indicated the hydrophobicity is important to the bioactivity. Three dimension quantitative structure-activity relationship （3D-QSAR） studies were performed to highlight the structural require- ments of ASTanalogs, which demonstrated introduction of bulkier substituents on the N-terminus would increase the activity. Analog Ⅱ12 （IC50： 0.08 μmol/L） exhibited similar inhibitory activity to the lead B1, but its synthetic route was simpler than B1. Therefore, Ⅱ12 could be used as a new lead compound for the discovery eco-friendly IGRs.展开更多
文摘Background: Mosquitoes are responsible of numerous vector-borne diseases and among these diseases is malaria which takes away lives of thousands of people, especially children of under five, particularly in Africa. To reduce the mortality and economic burdens of this deadly disease, synthetic insecticide has been of use to control its main vector, Anopheles gambiae. Due to adverse effects caused by these conventional products on non-target organisms and the environment, plants have been of first choice as they proved their effectiveness against mosquitoes and are said to be eco-friendly and relatively safer. Therefore, the aim of this study was to screen the phytochemicals and determine the larvicidal and adult emergence exhibitory activities of Momordica charantia and Hyptis spicigera leaves extracts against Anopheles gambiae larvae. Methods: The WHO standard protocol for larvicidal activity and IGRs was followed up and concentrations from 500 - 2000 ppm for larvicidal and 500 - 1500 ppm for IGRs were set up. Results: There was the presence of alkaloids, flavonoids, tannins, phenols, steroids, terpenoids and oils in Momordica charantia against alkaloids, taponins, tannins, phenols, steroids, terpenoids and oils in Hyptis spicigera. Methanol crude extract registered the lowest LC<sub>50</sub> value of 270.6 ppm followed by ethyl acetate and hexane fractions recorded the LC<sub>50</sub> of 742.1 and 756 ppm, respectively for larvicidal activity of Momordica charantia against LC<sub>50</sub> of 760 and 867.5 ppm for hexane fraction and methanol crude extract, respectively for Hyptis spicigera. Methanol crude extract and hexane fraction of both plants as well as the ethyl acetate fraction of M. charantia registered greater emergence inhibition with IE<sub>50</sub> values of 590.2, 842.3 and 982 ppm for methanol crude extract, hexane and ethyl acetate fractions of M. charantia, respectively against 901.7 and 873.2 for methanol crude extract and hexane fraction of H. spicigera, respectively. Conclusion: The toxicity a
文摘Background: Anopheles gambiae is enemy number one of mankind in Africa and particularly in Cameroon due to its ability of transmitting malaria which is the deadliest disease in this part of the world. Synthetic insecticides have been used to control malaria vectors but they have negative effects on non-target organisms and are environmentally unfriendly. Control of mosquitoes at larval stages using phytochemicals is currently the leading tool to reduce the mosquito population and so the reduction of malaria transmission rates. Therefore, the present study was to evaluate the phytochemical contents, larvicidal and adult emergence inhibition activities of Balanites aegyptiaca seed and Aristolochia albida root solvents extracts against Anopheles gambiae larvae. Methods: The World Health Organization standard protocols were followed for the different bioassays. Concentrations ranging from 500 - 2000 ppm for larvicidal and 500 - 1500 ppm for IGRs were used. Results: Both plants showed the presence of alkaloids, flavonoids, saponins, tannins, phenols, terpenoids and oils except the absence of phenols in Aristolochia albida. The larvicidal activity of Aristolochia albida extracts showed that hexane and methanol fractions were the most active killing relatively all exposed larvae with the LC<sub>50</sub> values of 420.1 and 453 ppm, respectively. The same observation was made in hexane fraction from Balanites aegyptiaca (LC<sub>50</sub> = 588 ppm). The insect growth inhibitory activity of Aristolochia albida extracts proved that hexane and methanol fractions relatively caused a 100% inhibition in the mosquito development, recording the EI<sub>50</sub> values of 482.4 and 555.6 ppm, respectively. The same trend was observed with Balanites aegyptiaca hexane fraction registering better EI<sub>50</sub> of 623.9 ppm. Conclusions: Our findings demonstrate that Balanites aegyptiaca seed and Aristolochia albida seed extracts are rich in phytochemicals capable of killing mosquito larvae and disrupting mosquito larval development.
文摘The comprehensive knowledge that the delayed systemic and reproduction side effects can be even more deleterious than acute toxicity, has caused a shift in focus toward sublethal effects assessment on physiology and behavior of beneficial insects. In this study, we assessed the risks posed by some insecticides with different mode of action through lethal and delayed systemic sublethal effects on the pupation, adult emergence, and repro- duction of the chrysopid Chrysoperla externa （Hagen, 1861; Neuroptera： Chrysopidae）, an important predator in pest biological control. The maximum field recommended dose （MFRD） and twice （2xMFRD） for chlorantraniliprole, tebufenozide, and pyriproxyfen were harmless to C. externa. In contrast, all the tested chitin synthesis inhibitors （CSIs） were highly detrimental to the predator, despite of their lack of acute lethal toxicity. There- fore, the safety assumed by using IGRs toward beneficial insects is not valid for chrysopids. Dose-response data showed that although all CSIs have a similar mechanism of action, the relative extent of toxicity may differ （novaluron 〉 lufenuron 〉 teflubenzuron）. For CSIs, the delayed systemic effects became obvious at adult emergence, where the predicted no observable effect dose （NOED） was 1/2 048 of the MFRD for novaluron （0.085 ng/insect）, and 1/256 of the MFRD for both lufenuron （0.25 ng/insect） and teflubenzuron （0.6 ng/insect）. Finally, this work emphasized the significance of performing toxicity risk assessments with an adequate posttreatment period to avoid underestimating the toxicities of insecticides, as the acute lethal toxicity assays may not provide accurate information regarding the long-range effects of hazardous compounds.
基金financially supported by the National Natural Science Foundation of China(No.21372257)the grants from the National Key Research and Development Plan(No.2017YFD0200504)
文摘Allatostatins （ASTs）, a family of insect neuropeptide, can inhibit juvenile hormone （JH） biosynthesis by the corpora allata （CA） in Diploptera punctata, and therefore be regarded as potential leads for the discovery of new insect growth regulators （1GRs）. But several shortcomings, such as their sensitivity to peptidases and high cost, impeded their practical application in pest management. In order to discover new IGRs, one AST analog B1 possessing non-peptide group was discovered with high ability to inhibit JH biosynthesis in vitro （IC50： 0.09 μmol/L） in our previous studies. In the present work, two series of B1 analogs with different substituents on the N-terminus region were designed and synthesized. The result suggested that benzene showed better activity than other heterocycles, and the para-substitution on the benzene was beneficial for activity. Moreover, analogs with logP value over 2.0 exhibited good activity, which indicated the hydrophobicity is important to the bioactivity. Three dimension quantitative structure-activity relationship （3D-QSAR） studies were performed to highlight the structural require- ments of ASTanalogs, which demonstrated introduction of bulkier substituents on the N-terminus would increase the activity. Analog Ⅱ12 （IC50： 0.08 μmol/L） exhibited similar inhibitory activity to the lead B1, but its synthetic route was simpler than B1. Therefore, Ⅱ12 could be used as a new lead compound for the discovery eco-friendly IGRs.
