Effects of the novel acaricide acynonapyr on the calcium-activated potassium channel.

Resistance to insecticides and acaricides is a major impediment to effectively controlling insect pests worldwide. These pests include the two-spotted spider mite Tetranychus urticae (T. urticae), which exists globally. This polyphagous herbivore causes major agricultural problems and can develop resistance to the agents above. Therefore, the continuous development of acaricides with new modes of action is important to circumvent the resistance of insects to pesticides. Acynonapyr is a novel class of acaricides containing an azabicyclo ring. In this study, we determined the activity of acynonapyr and its analogs on calcium-activated potassium (KCa2) channels in two-spotted spider mites using electrophysiological techniques (patch-clamp). We also examined their acaricidal efficacy against mites in the laboratory. The acynonapyr and analogs blocked T. urticae KCa2 (TurKCa2) channels in a concentration-dependent manner. A comparison of acaricidal activity against T. urticae with inhibitory activity against TurKCa2 revealed that TurKCa2 channels are the primary toxicological targets. Finally, we examined the effect of acynonapyr on Homo sapiens KCa2 (HsaKCa2.2) channels and demonstrated that the compound at 10 µM had a limited effect on the activity of this channel.

Discovery of a novel acaricide, acynonapyr.

Acynonapyr, discovered by Nippon Soda Co., Ltd., is a novel acaricide with N-pyridyloxy azabicycle as a unique core structure. Acynonapyr exhibits high activity against the spider mite species in the genera Tetranychus and Panonychus, with good efficacy at all life stages. Early in this research, cyclic amines substituted with (hetero)aryl(oxy) moieties were designed as target molecules and diversely synthesized, and 4-[4-(trifluoromethyl)phenoxy]-1-[5-(trifluoromethyl)-2-pyridyl]piperidine was found to show weak acaricidal activity. The structural optimization of this acaricidal active piperidine as the first lead compound led to the discovery of acynonapyr. In this report, our research process that led to the discovery of acynonapyr is described.