Acaricide fenazaquin

For the acaricide fenazaquin [4-(4-tert-butylphenethoxy)quinazoline], a potent inhibitor of electron transport at complex I (see Section 28.1.3), an additional low-affinity binding site in the stalk region of ATP synthase has been recently identified. The relevance of this newly discovered binding site is unknown since the enzymatic activity of ATP synthase is not impaired [12]. 

In contrast to the mammalian and avian studies, the available information on the metabolism of the spinosyns by insects suggests that metabolism of the spinosyns (e.g., spinosyn A) is very limited. Studies of spinosyn A metabolism in tobacco budworm Heliothis virescens) larvae show that the only component detected (within the limits of detection, up to 24 h post treatment) in larval homogenates of topically treated larvae was the parent, spinosyn A [53, 54]. In contrast, these same larvae readily metabolized the acaricide fenazaquin [3, 53], clearly demonstrating that H. virescens larvae have the capacity to metabolize xenobiotics. Further, studies with H. virescens larvae highly resistant to spinosad [55] also found no evidence for metabolism of spinosyn A [56, 57]. 

Quinazoline acaricides are derivatives of quinazoline. Fenazaquin is the only member of this unique class. It is a contact and stomach poison acaricide used for control of all stages of mites on cotton, stone and pome fruits, citrus, grapes, and ornamentals. Its oral LD50 in rats is 134-138 mg/kg. 

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