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

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 2mM. 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±0.0504mM. 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.