Structure-activity relationships of 33 piperidines as toxicants against female adults of Aedes aegypti (Diptera: Culicidae)

Aedes aegypti (L.) (Diptera: Culicidae) is the primary vector of both dengue and yellow fever. Use of insecticides is one of the primary ways to control this medically important insect pest. However, few new insecticides have been developed for mosquito control in recent years. As a part of our collaborative effort to search for new insecticides to control mosquitoes, piperidine was used as base compound for further optimization. Herein, we report the structure-activity relationships of 33 piperidines against adult female Ae. aegypti. On the basis of 24-h LD50 values after topical application, the most toxic compound was 2-ethyl-piperidine, with an LD50 as low as 0.8 microg per mosquito. The toxicities of piperidine derivatives were significantly decreased when a benzyl moiety was attached to the carbon of the piperidine ring, with an LD50 value as high as 29.2 microg per mosquito. The toxicity order of three moieties attached to the carbon of the piperidine ring was ethyl- > methyl- > benzyl-derivatives. When the same moiety was attached to the piperidine ring, the carbon position to which the moiety was attached conferred different toxicity and the toxicity order was second carbon > third carbon > fourth carbon. Together, these preliminary results may be useful in guiding further piperidine ring modifications in the development of potential new insecticides.