Effects of introducing theanine or glutamic acid core to tralopyril on systemicity and insecticidal activity

- Four new conjugates that contain tralopyril and theanine or glutamic acid moieties showed phloem mobility but no tough phytotoxicity problem to tea shoots.
- Only conjugate 20 exhibited activity against Plutella xylostella.
- Conjugate 20 showed obviously systemic insecticidal activity against Dendrothrips minowai Priesner, while chlorfenapyr showed no attribute of that.
- A novel design strategy of pro-insecticide for improved phloem systemicity was provided.

Tralopyril was the active agent of a pro-insecticide chlorfenapyr. To simultaneously solve the problems of the phytotoxicity and non-systemic insecticidal activity of tralopyril, four new tralopyril conjugates containing theanine or glutamic acid moieties were designed and synthesized. Their phytotoxicity to tea shoot, phloem systemicity, and insecticidal activity were evaluated. Phytotoxic symptoms were not observed after the tea shoots were exposed to the four conjugates at concentrations of 2 mM. The phloem mobility test on Ricinus communis L. seedlings confirmed that all four conjugates were mobile in the sieve tubes. Results of insecticidal activity against the third-instar larvae of Plutella xylostella showed that only conjugate 20 exhibited activity with an LC50 value of 0.5882 ± 0.0504 mM. After root application to tea seedlings, conjugate 20 showed obviously systemic insecticidal activity against Dendrothrips minowai Priesner, while chlorfenapyr showed no attribute of that. A new conjugate as potential phloem mobile pro-insecticide candidate was provided and so a novel strategy of pro-insecticide for improved phloem systemicity was proposed.

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