To define acaricidal mechanism of a new acaricidal AKD-2023 (2-acetoxy-3-n-dodecyl-l, 4naphthoquinone) and its metabolite, DHN (2-hydroxy-3-n-dodecyl-l, 4-naphthoquinone), the effects of these compounds on the respiration of flight-muscle mitochondria isolated from house flies were investigated. The inhibitory potency of AKD-2023 for succinate and pyruvate oxidation activity was much less than that of DHN. This result suggested that the hydrolyzed metabolite, DHN is virtually biologically active and inhibits the respiration of mitochondria. It was also proved that the inhibition occurs at the complex III in mitochondrial electron transfer chain. On the basis of reduction kinetics of cytochromes b and c1, the binding site was shown to be ubiquinol oxidation site (Q0 center) of complex III, being different from that of other acaricides developed recently.

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