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

The application of some reported inhibitors against the chitinolytic enzyme Of 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 Of ChtI. Novel rhodanine compounds IAa-f and IBa-f have weak aqueous solubility, but they (IAd: Ki = 4.0 µM; IBd: Ki = 2.2 µM) showed better inhibitory activities against Of ChtI and comparable insecticidal efficiency toward Ostrinia furnacalis compared to the high aqueous solubility compounds IIAa-f and IIBa-f (IIAd: Ki = 21.6 µM; IIBd: Ki = 14.3 µM) without a large conjugate plane. Further optimized compounds IIIAa-j with a conjugate plane as well as a higher aqueous solubility exhibited similar good inhibitory activities against Of ChtI (IIIAe: Ki = 2.4 µM) and better insecticidal potency (IIIAe: mortality rate of 63.33%) compared to compounds IAa-f and IBa-f, 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 Of ChtI. This study provides a new strategy for designing insect chitinolytic enzyme inhibitors as insect growth regulators for pest control.

Discovery of novel isopropanolamine inhibitors against MoTPS1 as potential fungicides with unique mechanisms.

The resistance and ecotoxicity of fungicides seriously restrict our ability to effectively control Magnaporthe oryzae. Discovering fungicidal agents based on novel targets, including MoTPS1, could efficiently address this situation. Here, we identified a hit VS-10 containing an isopropanolamine fragment as a novel MoTPS1 inhibitor through virtual screening, and forty-four analogs were synthesized by optimizing the structure of VS-10. Utilizing our newly established ion-pair chromatography (IPC) and leaf inoculation methods, we found that compared to VS-10, its analog j11 exhibited substantially greater inhibitory activity against both MoTPS1 and the pathogenicity of M. oryzae. Molecular simulations clarified that the electrostatic interactions between the bridging moiety of isopropanolamine and residue Glu396 of contributed significantly to the binding of j11 and MoTPS1. We preliminarily revealed the unique fungicidal mechanism of j11, which mainly impeded the infection of M. oryzae by decreasing sporulation, killing a small portion of conidia and interfering with the accumulation of turgor pressure in appressoria. Thus, in this study, a novel fungicide candidate with a unique mechanism targeting MoTPS1 was screened and discovered.

Discovery of piperonyl-tethered sulfoximines as novel low bee-toxicity aphicides targeting Amelα1/ratß2 complex.

Nicotinic acetylcholine receptor (nAChR) is recognized as a significant insecticide target for neonicotinoids and some agonists. In this study, the nAChR α1 subunit from Apis mellifera was first found to be narrowly tuned to different bee toxicity insecticides, namely, sulfoxaflor (SFX) and flupyradifurone (FPF). Hence, novel sulfoximine derivatives 7a-h were rationally designed and synthesized by introducing a benzo[d][1,3]dioxole moiety into a unique sulfoximine skeleton based on the binding cavity characteristics of Amelα1/ratß2. The two electrode voltage clamp responses of 7a-h were obviously lower than that of SFX, indicating their potentially low bee toxicity. Besides, representative compounds 7b and 7g exhibited low bee toxicity (LD50 > 11.0 µg/bee at 48 h) revealed by acute contact toxicity bioassays. Molecular modelling results indicated that Ile152, Ala151, and Val160 from honeybee subunit Amelα1 and Lys144 and Trp80 from aphid subunit Mpα1 may be crucial for bee toxicity and aphicidal activity, respectively. These results clarify the toxic mechanism of agonist insecticides on nontargeted pollinators and reveal novel scaffold sulfoximine aphicidal candidates with low bee toxicity. These results will provide a new perspective on the rational design and highly effective development of novel eco-friendly insecticides based on the structure of the nAChR subunit.

Rational design of near-infrared ratiometric fluorescent probes for real-time tracking of ß-galactosidase in vivo.

ß-Galactosidase (ß-gal) is a hydrolytic enzyme in lysosomes and is also an important biomarker of cellular senescence and primary ovarian cancer. Therefore, real-time non-invasive detection of ß-gal activity in vivo is of great significance for the prevention of cell senescence and early diagnosis of ovarian cancer. We designed an enzyme-activated proportional near-infrared (NIR) probe (Gal-Br-NO2) for real-time fluorescence quantification and capture of ß-gal activity in vivo. The main characteristics of the Gal-Br-NO2 probe include short response time (less than 10 min), large Stokes displacement (155 nm), and near-infrared fluorescence emission (670 nm). The probe has also been successfully used to detect ß-gal in ovarian cancer cells and senile cells and can accurately detect endogenous ß-gal in zebrafish. Our work provides a potential tool for pre-clinical real-time tracking of ß-gal activity in vivo and early diagnosis of disease.

Rational Design and Identification of Novel Piperine Derivatives as Multichitinase Inhibitors.

Asian corn borer (Ostrinia furnacalis) is one of the most destructive pests in agriculture. Three chitinases OfChtI, OfChtII, and OfChi-h are regarded as potential targets for discovering novel agrochemicals to control O. furnacalis. In this study, piperine (Ki = 43.78∼83.03 µM) was first shown to exhibit inhibitory activities against all three chitinases. Subsequently, 19 novel piperine derivatives were rationally designed based on the conserved aromatic residues of three chitinases and then synthesized. Among them, Compound 5k (Ki = 11.78∼22.82 µM) was identified as the most effective multichitinase inhibitor and indeed displayed higher insecticidal activity against O. furnacalis than dual- or single-chitinase inhibitors. Molecular mechanism studies clarified that Compound 5k interacted with two conserved TRP and TYR of three chitinases in identical modes through hydrogen bonds, hydrophobic, and π-π interactions. Moreover, the microinjection experiment indicated that Compound 5k exhibited substantial sublethal effects against O. furnacalis by regulating its growth and development. This study provides evidence of multichitinase inhibitors to be applied in the control of O. furnacalis.