Structure-oriented molecular extension strategies unlock C-glycoside insecticides targeting OfChtII and OfHex1.

Chitinase, a critical enzyme in insect growth and development, is recognized as an ideal target for green insecticides. In this study, leveraging B12 as a lead compound, 21 novel C-glycoside triazoles targeting chitin-degrading enzymes were designed and synthesized via a molecular elongation strategy combined with efficient click chemistry. Among them, compound C7 was uniquely designed by incorporating a nitrobenzofurazan (NBD) moiety, which enabled strong face-to-face π-π stacking with Trp1621 in the active site of OfChtII, a key interaction absent in B12. All compounds were structurally characterized, and their inhibitory activities against chitin-degrading enzymes (OfChtII and OfHex1) were evaluated. Additionally, their insecticidal efficacy was assessed against two economically significant lepidopteran pests (Plutella xylostella and Ostrinia furnacalis). As a result of its optimized binding mode, compound C7 was identified as the most potent inhibitor, with Ki values of 1.31 μM and 4.39 μM against OfChtII and OfHex1, respectively, representing a 30.69-fold and 3.46-fold improvement over the lead compound B12. Furthermore, C7 demonstrated excellent insecticidal efficacy, strongly suppressing larval growth (36.22 % and 38.11 % reduction in body length) and causing high mortality (100 % and 82.14 %) in Plutella xylostella and Ostrinia furnacalis, respectively. The inhibition mechanism was elucidated through multiple means, including molecular docking, molecular dynamics simulations, MMPBSA calculations and DFT, revealed that stable π-stacking with the active sites of the enzymes were responsible for its high efficiency. This study provides a promising lead compound and theoretical insights for the development of C-glycoside pesticides targeting chitinase.