Enantioselectivity Mechanism of Etoxazole Enantiomers in Tetranychus cinnabarinus: Acaricidal Activity, Metabolic Difference, and Target Binding

Etoxazole, a widely used mite growth inhibitor, contains a chiral center in its chemical structure, resulting in two mirror-image enantiomers. These enantiomers of etoxazole display significant differences in biological activity and environmental behavior. In bioassays conducted against Tetranychus cinnabarinus, it was observed that S-etoxazole demonstrated approximately 279.63 times greater activity against mite eggs compared to R-etoxazole, and its efficacy against adult mites was approximately 5 times higher than that of R-etoxazole. Furthermore, S-etoxazole was found to be more potent in inhibiting chitin synthesis. To elucidate the underlying mechanism for the observed differences in enantiomeric activity, we conducted metabolism assays using crude enzymes, revealing that R-etoxazole undergoes metabolism more readily than S-etoxazole. Subsequent molecular docking and Microscale Thermophoresis (MST) experiments showed that R-etoxazole exhibits weaker binding affinity to the target protein, chitin synthase 1, compared to S-etoxazole. This study thus demonstrates that the differential enantiomeric activity of etoxazole was attributable to a combination of factors, including detoxification metabolism and target protein binding.