To explore lead compounds for biological insecticides, nine fatty acids (FAs)' insecticidal activities against Helicoverpa zea (Lepidoptera, Noctuidae) and their cytotoxicity on H. zea neuronal cells (AW1 cells) were evaluated. The results showed that FAs at 1000 mg/L had a mortality rate of 10.0-83.33% and an inhibitory rate on AW1 cells with IC50 values of 74.6-287.37 μM. Particularly, lauric acid exhibited the most excellent bioactivity both in vivo and in vitro among nine FAs. Further, its mode of action was investigated on the AW1 cells, and the results showed that lauric acid induced apoptosis on the AW1 cells, involving a decrease of mitochondrial membrane potential (ΔΨm) and an increase of caspase-9/3 activity and reactive oxygen species (ROS) levels. Furthermore, by detecting the expression of apoptosis protein, we found that the levels of Bcl-2 fell whereas the levels of cytochrome c and Bax rose remarkably. These results showed that FAs such as lauric acid could be potential lead compounds with a novel mode of action and highly insecticidal activity against H. zea.
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