Engineering a photoswitchable acaricidal agent by the integration of an azobenzene moiety with a bifenazate structure

Photopharmacology achieves precise photo controlled regulation of drug activity by utilizing the properties of photochromic ligands. In this study, a series of novel azobenzene-based photochromic ligands (ABB1-5) were designed and synthesized, and their biological activities were confirmed to be precisely regulated by light irradiation. Bioassays against larvae of Culex pipiens pallens showed that the activity of ABB1 was significantly enhanced after light exposure, with the median lethal concentration (LC₅₀) decreasing from 27.20 μg/mL before irradiation to 16.99 μg/mL after, a reduction of 10.21 μg/mL, yielding a difference coefficient of 1.60. Similarly, experiments on Tetranychus cinnabarinus demonstrated a remarkable decrease in acaricidal activity for ABB4 after irradiation, as evidenced by an increase in LC₅₀ from 7.01 to 18.40 μg/mL, an increase of 11.39 μg/mL, with a difference coefficient of 2.62. Notably, the light-induced differences in activity exhibited by the ABBs series against both C. pipiens pallens larvae and T. cinnabarinus not only validate the potential of photochromic ligands in the precise optical control of drug efficacy but also offer a novel strategy for delaying the development of resistance to acaricides in phytophagous mites.