In this study, a new emulsifier
precursor was prepared via esterification of avermectin with succinic
anhydride. The chemical structure of the product was confirmed to
be monosubstituted avermectin. After neutralization with triethanolamine,
it exhibited adequate emulsification ability for avermectin. Avermectin
was then encapsulated in nanoparticles in the nanoemulsion with a
high drug loading up to 60 wt % and high stability. The nanoemulsion
of nanoparticles that serves as a carrier of avermectin shows highly
efficient pesticide characteristics, including low surface tension,
high affinity to leaves, and improved photostability. In the presence of esterase or under strongly basic conditions, the
ester bonds of the emulsifier can be hydrolyzed, and the encapsulated
avermectin molecules can be released in an accelerated manner. The
nanoemulsion exhibited improved insecticidal effect compared with
commercial emulsifiable concentrate, which was attributed to the cleavage
of ester bonds of the emulsifier by esterase in vivo
