Design, synthesis, biologically evaluation and molecular docking of C-glycosidic oximino carbamates as novel OfHex1 inhibitors

The inhibition of function-specific β-N-acetyl-D-hexosaminidases, such as OfHex1 from the Asian corn borer (Ostrinia furnacalis), is a promising strategy for the development of green pesticides. Among reported OfHex1 inhibitors, glycosyl inhibitors show especially high inhibitory activity. In this study, a series of novel C-glycosidic oximino carbamate derivatives were designed using the OfHex1 crystal structure and synthesized. Among the C-Glycoside derivatives studied, compound 7k exhibited the best inhibitory activity against OfHex1 (IC₅₀ = 47.47 μM). Compound 7k also exhibited excellent larvicidal activity against Plutella xylostella. The potential inhibitory mechanism of 7k was studied using molecular docking. Notably, compound 7k is the first reported C-glycoside inhibitor of OfHex1. These results provide direction for the rational design of novel OfHex1 inhibitors.

Discovery of Biphenyl-Sulfonamides as Novel β-N-Acetyl-d-Hexosaminidase Inhibitors via Structure-Based Virtual Screening

Novel insecticidal targets are always in demand due to the development of resistance. OfHex1, a β-N-acetyl-d-hexosaminidase identified in Ostrinia furnacalis (Asian corn borer), is involved in insect chitin catabolism and has proven an ideal target for insecticide development. In this study, structure-based virtual screening, structure simplification, and biological evaluation are used to show that compounds with a biphenyl-sulfonamide skeleton have great potential as OfHex1 inhibitors. Specifically, compounds 10k, 10u, and 10v have K_i values of 4.30, 3.72, and 4.56 μM, respectively, and thus, they are more potent than some reported nonglycosyl-based inhibitors such as phlegmacin B₁ (K_i = 26 μM), berberine (K_i = 12 μM), 2 (K_i = 11.2 μM), and 3 (K_i = 28.9 μM). Furthermore, inhibitory kinetic assessments reveal that the target compounds are competitive inhibitors with respect substrate, and based on toxicity predictions, most of them have potent drug properties. The obtained results indicate that the biphenyl-sulfonamide skeleton characterized by simple chemical structure, synthetic tractability, potent activity, and low toxicity has potential for further development in pest management targeting OfHex1.

Virtual screening, synthesis, and bioactivity evaluation for the discovery of β-N-acetyl-D-hexosaminidase inhibitors

BACKGROUND

Molting is an essential insect developmental process, in which a variety of enzymes are involved. The inhibition of these enzymes effect normal insect growth and development and may even cause death. OfHex1, one of the β-N-acetyl-D-hexosaminidases, is a key enzyme involved in the molting process of the Asian corn borer (Ostrinia furnacalis), and is deemed a potential insecticidal target.

RESULTS

Based on the crystal structure of OfHex1, virtual screening was carried out to obtain a novel class of OfHex1 inhibitors, of which, 28 compounds were subjected to bioactivity evaluation. The compound 3, N-(3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophen-2-yl)benzamide, showed good inhibition against OfHex1 with a K_i value of 11.2 μM. Structure optimization and molecular docking were applied for the structure-activity relationship analysis. The results also showed that the cyano group of this compound was essential for the maintenance of its inhibitory activity against OfHex1. Additionally, the interaction between this compound and Trp490, Glu328, Tyr475 and Trp524 were important for inhibitory activity.

CONCLUSION

The advantages of the derivatives of 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile, which have simple chemical structures and are easily synthesized, suggests them to be developed further as potential OfHex1 inhibitors for pest control. © 2020 Society of Chemical Industry.

Glycosyl triazoles as novel insect β-N-acetylhexosaminidase OfHex1 inhibitors: Design, synthesis, molecular docking and MD simulations

The insect enzyme GH20 β-N-acetyl-d-hexosaminidase OfHex1 represents an important chitinolytic enzyme found in the agricultural pest Ostrinia furnacalis (Guenée) and inhibition of this enzyme has been considered a promising strategy for the development of eco-friendly pesticides. In this article, based on the structure of the catalytic domains of OfHex1, a series of novel glycosyl triazoles were designed and synthesized via Cu-catalyzed azide-alkyne [3+2] cycloaddition reaction. To investigate the potency and selectivity of these glycosyl triazoles, the inhibition activities towards OfHex1 and HsHexB (human β-N-acetylhexosaminidase B) were studied. Particularly compound 17c (OfHex1, K_i = 28.68 μM; HsHexB, K_i > 100 μM) exhibited a suitable activity and selectivity against OfHex1. Furthermore, the possible inhibitory mechanisms of 17c with OfHex1 were studied using molecular docking and MD simulations. The structure-activity relationship results as well as the formed binding patterns may provide promising insights into the further development of novel OfHex1 inhibitors.

Development of Unsymmetrical Dyads As Potent Noncarbohydrate-Based Inhibitors against Human β-N-Acetyl-d-hexosaminidase

Human β-N-acetyl-d-hexosaminidase has gained much attention due to its roles in several pathological processes and been considered as potential targets for disease therapy. A novel and efficient skeleton, which was an unsymmetrical dyad containing naphthalimide and methoxyphenyl moieties with an alkylamine spacer linkage as a noncarbohydrate-based inhibitor, was synthesized, and the activities were valuated against human β-N-acetyl-d-hexosaminidase. The most potent inhibitor exhibits high inhibitory activity with K i values of 0.63 μM. The straightforward synthetic manners of these unsymmetrical dyads and understanding of the binding model could be advantageous for further structure optimization and development of new therapeutic agents for Hex-related diseases.

Identification of novel potential β-N-acetyl-D-hexosaminidase inhibitors by virtual screening, molecular dynamics simulation and MM-PBSA calculations

Chitinolytic β-N-acetyl-d-hexosaminidases, as a class of chitin hydrolysis enzyme in insects, are a potential species-specific target for developing environmentally-friendly pesticides. Until now, pesticides targeting chitinolytic β-N-acetyl-d-hexosaminidase have not been developed. This study demonstrates a combination of different theoretical methods for investigating the key structural features of this enzyme responsible for pesticide inhibition, thus allowing for the discovery of novel small molecule inhibitors. Firstly, based on the currently reported crystal structure of this protein (OfHex1.pdb), we conducted a pre-screening of a drug-like compound database with 8 × 10⁶ compounds by using the expanded pesticide-likeness criteria, followed by docking-based screening, obtaining 5 top-ranked compounds with favorable docking conformation into OfHex1. Secondly, molecular docking and molecular dynamics simulations are performed for the five complexes and demonstrate that one main hydrophobic pocket formed by residues Trp424, Trp448 and Trp524, which is significant for stabilization of the ligand–receptor complex, and key residues Asp477 and Trp490, are respectively responsible for forming hydrogen-bonding and π–π stacking interactions with the ligands. Finally, the molecular mechanics Poisson–Boltzmann surface area (MM-PBSA) analysis indicates that van der Waals interactions are the main driving force for the inhibitor binding that agrees with the fact that the binding pocket of OfHex1 is mainly composed of hydrophobic residues. These results suggest that screening the ZINC database can maximize the identification of potential OfHex1 inhibitors and the computational protocol will be valuable for screening potential inhibitors of the binding mode, which is useful for the future rational design of novel, potent OfHex1-specific pesticides.