Discovery of Rhodanine Inhibitors Targeting ChtI Based on the π-Stacking Effect and Aqueous Solubility.

The application of some reported inhibitors against the chitinolytic enzyme ChtI was limited due to their unsatisfactory insecticidal activities. Hence, we first performed a synergetic design strategy combining the π-stacking effect with aqueous solubility to find novel rhodanine analogues with inhibitory activities against ChtI. Novel rhodanine compounds and have weak aqueous solubility, but they (: = 4.0 μM; : = 2.2 μM) showed better inhibitory activities against ChtI and comparable insecticidal efficiency toward compared to the high aqueous solubility compounds and (: = 21.6 μM; : = 14.3 μM) without a large conjugate plane. Further optimized compounds with a conjugate plane as well as a higher aqueous solubility exhibited similar good inhibitory activities against ChtI (: = 2.4 μM) and better insecticidal potency (: mortality rate of 63.33%) compared to compounds and , respectively. Molecular docking studies indicated that the conjugate planarity with the π-stacking effect for rhodanine analogues is responsible for their enzyme inhibitory activity against ChtI. This study provides a new strategy for designing insect chitinolytic enzyme inhibitors as insect growth regulators for pest control.