Azobenzene-isoxazoline as photopharmacological ligand for optical control of insect GABA receptor and behavior

Recent Research Progress in Oxime Insecticides and Perspectives for the Future

In recent decades, the unique structural attributes and purported insecticidal properties of oximes have garnered increasing attention. A variety of insecticides, encompassing fluxametamide, fluhexafon, and lepimectin, have been synthesized, all of which incorporate oximes. This review endeavors to encapsulate the insecticidal efficacy, structure-activity correlations, and operative mechanisms of oxime-containing compounds. Furthermore, it delves into the conceptual frameworks underpinning the design of innovative oxime-based insecticides, thereby shedding light on prospective advancements in this field.

Optical Control of Insect Behavior and Receptors with Azobenzene-Bridged Fipronil and Imidacloprid

Photopharmacology can be implemented in a way of regulating drug activities by light-controlling the molecular configuations. Three photochromic ligands (PCLs) that bind on one or two sites of GABARs and nAChRs were reported here. These multiphoton PCLs, including FIP-AB-FIP, IMI-AB-FIP, and IMI-AB-IMI, are constructed with an azobenzene (AB) bridge that covalently connects two fipronil (FIP) and imidacloprid (IMI) molecules. Interestingly, the three PCLs as well as FIP and IMI showed great insecticidal activities against Aedes albopictus larvae and Aphis craccivora. IMI-AB-FIP in both trans/cis isomers can be reversibly interconverted depending on light, accompanied by insecticidal activity decrease or increase by 1.5-2.3 folds. In addition, IMI-AB-FIP displayed synergistic effects against A. craccivora (LC50, IMI-AB-FIP = 14.84-22.10 μM, LC50, IMI-AB-IMI = 210.52-266.63 μM, LC50, and FIP-AB-FIP = 36.25-51.04 μM), mainly resulting from a conceivable reason for simultaneous targeting on both GABARs and nAChRs. Furthermore, modulations of wiggler-swimming behaviors and cockroach neuron function were conducted and the results indirectly demonstrated the ligand-receptor interactions. In other words, real-time regulations of receptors and insect behaviors can be spatiotemporally achieved by our two-photon PCLs using light.

Design, synthesis and insecticidal activity of novel Isoxazoline Acylhydrazone compounds

BACKGROUND

Nowadays, the diamondback moth has ascended to become one of the most formidable pests plaguing cruciferous vegetables. Consequently, the exigency for the development of efficacious pesticide candidates for crop protection has never been more paramount. In response to this pressing need, this study presents a compendium of novel isoxazoline derivatives, incorporating acylhydrazone moieties, synthesized with the express purpose of serving as potential insecticides.

RESULTS

The structures of these derivatives were confirmed using Proton nuclear magnetic resonance (1 H NMR), Carbon-13 nuclear magnetic resonance (13 C NMR), and high-resolution mass spectrometry (HR-MS). Most of these derivatives demonstrated effective insecticidal activities against Plutella xylostella. Notably, compound E3 exhibited exceptional insecticidal activity against Plutella xylostella (LC50  = 0.19 mg L-1 ), surpassing the effectiveness of ethiprole (LC50  = 3.28 mg L-1 ), and comparable to that of fluxametamide (LC50  = 0.22 mg L-1 ). Interestingly, compound E3 also displayed potent insecticidal activity against Pyrausta nubilalis (LC50  = 0.182 mg L-1 ) and Chilo suppressalis (LC50  = 0.64 mg L-1 ), and the LC50 values of fluxametamide were 0.23 mg L-1 (P. nubilalis) and 2.26 mg L-1 (C. suppressalis), respectively. The molecular docking results revealed that the compound E3 can form a hydrogen bond and two Pi-Pi bonds with the active sites of GABA receptors. In addition, the DFT calculations were also performed to study the relationship between insecticidal activities. The structure-activity relationships suggested that the identity of the R substituent was crucial for their pesticidal activities.

CONCLUSION

The results of the present study suggest that isoxazoline acylhydrazone derivatives could be promising candidates against P. xylostella and other Lepidopteran pests. © 2023 Society of Chemical Industry.

Design, Synthesis, and Insecticidal Activity of Novel Isoxazoline Diacylhydrazine Compounds as GABA Receptor Inhibitors

A series of isoxazoline derivatives containing diacylhydrazine moieties were designed and synthesized as potential insecticides. Most of these derivatives exhibited good insecticidal activities against Plutella xylostella, and some compounds exhibited excellent insecticidal activities against Spodoptera frugiperda. Especially, D14 showed outstanding insecticidal activity against P. xylostella (LC₅₀ = 0.37 μg/mL), which was superior to that of ethiprole (LC₅₀ = 2.84 μg/mL) and tebufenozide (LC₅₀ = 15.3 μg/mL) and similar to that of fluxametamide (LC₅₀ = 0.30 μg/mL). Remarkably, the insecticidal activity of D14 against S. frugiperda (LC₅₀ = 1.72 μg/mL) was superior to that of chlorantraniliprole (LC₅₀ = 3.64 μg/mL) and tebufenozide (LC₅₀ = 60.5 μg/mL) but lower than that of fluxametamide (LC₅₀ = 0.14 μg/mL). The results of electrophysiological experiments, molecular docking, and proteomics experiments indicate that compound D14 acts by interfering with the γ-aminobutyric acid receptor to control pests.

Machine learning-based approach for prediction of ion channels and their subclasses

Ion channels are ion-permeable protein pores that are found in all cell lipid membranes. Distinct ion channels play multiple roles in biological processes. Proteomic data is fast accumulating as a result of the fast growth of mass spectrometry and giving us the chance to comprehensively explore ion channel classes along with their subclasses. This paper proposes an eXtreme Gradient Boosting (XGBoost)-based method to estimate the ion channel classes and their subclasses. Here, 12 feature vectors are applied to better characterize protein sequences like amino acid composition, pseudo-amino acid composition, normalized moreau-broto autocorrelation, amphiphilic pseudo-amino acid composition, dipeptide composition, Geary autocorrelation, tripeptide composition, sequence-order-coupling number, composition/transition/distribution, conjoint triad, moran autocorrelation, quasi-sequence-order descriptors. Here, a total of 9920 features are extracted from the protein sequence. The principal component analysis is applied to determine the optimal number of features to optimize the performance. In 10-fold cross-validation the proposed XGBoost based approach with optimal 50 features achieved accuracy of 100%, 98.70%, 98.77%, 97.26%, 87.40%, 97.39%, 98.03%, 96.42%, and F1-Score of 100%, 99%, 99%, 97%, 87%, 97%, 98%, 97%, for prediction of ion channel and nonion channel, voltage-gated and ligand-gated ion channels, subclasses of voltage-gated ion channels (VGICs), subclasses of ligand-gated ion channels (LGICs), subclasses of voltage-gated calcium channels (VGCCs), subclasses of voltage-gated potassium channels (VGKCs), subclasses of voltage-gated sodium channels (VGSCs), and subclasses of voltage-gated chloride channels, respectively. Here the proposed approach also compares with the other approaches such as support vector machine, k-nearest neighbor, Gaussian Naïve Bayes, and random forest and also compares with existing methods such as support vector machine (SVM) with maximum relevance maximum distance with an accuracy of 86.6%, 83.7%, and 85.1%, for ion channels, non-ion channels and overall respectively and SVM with radial basis function kernel-based method with an accuracy of 100%, 97% and 99.9% for ion channels, nonion channels, and overall accuracy, respectively.

Synthesis of (E)/(Z)-Verbenone Oxime Ethers and Photoresponsive Behavior to Herbicidal Activity

The accumulation of residual active herbicides in the environment can cause a series of problems. It is thus meaningful to explore a photoresponsive herbicide, whose activity can be weakened under the action of light to reduce the negative effect. To this purpose, a series of (E)/(Z)-verbenone oxime ethers were designed, synthesized, and characterized. Oxime ether groups were adopted as the trigger switches. The preliminary screening for herbicidal activity showed that some of them exhibited better or comparable effects than that of the commercial herbicide flumioxazin against Brassica campestris and Echinochloa crusgalli. Meanwhile, five pairs of the target compounds with significantly different herbicidal effects between E- and Z-forms were further investigated for their reversible isomerization reaction and the accompanying variation of herbicidal activity. As a result, the maximum conversion rates were around 50%, and the herbicidal effect of the resulting mixture of E- and Z-isomers decreased outstandingly. The phototransformation mechanism of a pair of isomers (E)-4a and (Z)-4a was preliminarily explored. Besides, a reasonable and effective 3D-quantitative structure-activity relationship model (r² = 0.984 and q² = 0.571) was established and the binding mode was also investigated by molecular docking.

Optical Regulation of GABA Receptor by Visible Light via Azobenzene-Phenylpyrazole

Photopharmacology provides superior temporal and spatial resolution for the study of biological functions of γ-aminobutyric acid receptors (GABARs), and photopharmacology based on GABARs has significantly advanced the research of neurons and cells. Herein, we reported the azobenzene-phenylpyrazole (ABPs) for controlling the function of GABARs by light. The insecticidal activity of ABPs against Aedes albopictus larvae was different before and after light illumination. ABP3 (1 μM) could induce depolarization of dorsal unpaired median neurons and enable the real-time photoregulation of mosquito larval behavior. An electrophysiological experiment indicated that ABP3 had different inhibitory effects on GABARs before and after illumination. ABPs realized optical control of GABARs utilizing visible light, providing valuable supplements to the existing GABAR photocontrol tools.

Azobenzene-Avermectin B1a Derivatives for Optical Modulation of Insect Behaviors

Naturally occurring avermectins are allosteric modulators of glutamate-gated chloride channels (GluCls) and possess exceptionally potent anthelmintic, acaricidal, and insecticidal activities. Here, we develop photoswitchable azobenzene-avermectin (ABAVM) derivatives, which can be photoactivated upon ultraviolet irradiation. After illumination, the best compound p-AB4″AVM had a 1.88-fold and 2.74-fold insecticidal activity enhancement toward Culex pipiens pallens and Mythimna separata larvae, respectively. p-AB4″AVM allows for optical regulation of dorsal unpaired median neuron membrane potential with a 2.15-fold fluorescence intensity decrease after illumination. p-AB4″AVM and p-AB5AVM enable optical modulation of the behavioral response of Culex pipiens pallens larvae with 1- and 4-fold reduced mobility upon irradiation, respectively. The ABAVMs could be used to reversibly manipulate GluCls with light and may be useful for the mechanistic study of macrocyclic lactone insecticides.