Background:
It is one of the effective ways for pesticide innovation to develop new
insecticides from natural products as lead compounds. Quinine, the main alkaloid in the bark of
cinchona tree as well as in plants in the same genus, is recognized as a safe and potent botanical
insecticide to many insects. The structural modification of quinine into 9R-acyloxyquinine
derivatives is a potential approach for the development of novel insecticides, which showed more
toxicity than quinine. However, there are no reports on the insecticidal activity of 9Racyloxyquinine
derivatives to control Mythimna separata.
Methods:
Endeavor to discover biorational natural products-based insecticides, 20 novel 9Racyloxyquinine
derivatives were prepared and assessed for their insecticidal activity against M.
separata in vivo by the leaf-dipping method at 1 mg/mL.
Results:
Among all the compounds, especially derivatives 5i, 5k and 5t exhibited the best
insecticidal activity with final mortality rates of 50.0%, 57.1%, and 53.6%, respectively.
Conclusion:
Overall, a free 9-hydroxyl group is not a prerequisite for insecticidal activity and C9-
substitution is well tolerated; modification of out-ring double-bond is acceptable, and
hydrogenation of double-bond enhances insecticidal activity; Quinine ring is essential and open of
it is not acceptable. These preliminary results will pave the way for further modification of quinine
in the development of potential new insecticides.
Insecticidal action of the botanical insecticide wilforine on Mythimna separata (Walker) related with the changes of ryanodine receptor expression
