Design, Bioactivity and structure-activity of 3-Arylpropionate Derivatives as Potential High-Efficient Acaricides against Psoroptes Cuniculi

A series of 3-aryl propionic esters and their analogues were designed and evaluated for acaricidal activity in vitro against Psoroptes cuniculi, a mange mite. The structure–activity relationship (SAR) was also discussed. The results showed that 6 compounds possessed the excellent activity (LC(50) = 0.17–0.24 mM, LT(50) = 1.5–2.9 h), superior to ivermectin (LC(50) = 0.28 mM, LT(50) = 8.9 h) (P < 0.05), a standard drug. Furthermore, 7 compounds showed the good activity (LC(50) = 0.25–0.37 mM, LT(50) < 3.9 h), slightly lower or close to that of ivermectin. One compound displayed super-fast acaricidal property, far superior to ivermectin. SAR analysis found that the ester group is vital for the activity and the small steric hindrance adjacent to the ester group is advantageous for the high activity. The <C4 linear alcohol esters can give the higher activity. The substituents on the 3-phenyl ring or replacement of the 3-phenyl with heterocyclic aryl generally decreases the activity. The position of the ester group in the ester chain also influences the activity, where the 3-phenyl propionate and the benzoate had the highest and lowest activity, respectively. Thus, 3-arylpropionates emerged as new and promising high-efficient acaricide candidates.