Design, Synthesis, and Study of the Insecticidal Activity of Novel Steroidal 1,3,4-Oxadiazoles

Design, Synthesis of Dienthiazole Derivatives, and Evaluation of Aphicidal Activity

Nitrogen-containing heterocycles have attracted attention for the development of chemicals because of their many types, high physiological activities, and ease of synthesis. Aphids are severe pests found worldwide that cause serious losses in crop yield and quality every year. In this study, a series of novel dienolone thiazole derivatives were synthesized using dienolone acetate as the parent molecule. The synthesis involved bromination, Hantzsch reaction, esterification, deprotection, and other reactions. The structure of the compounds was determined using proton and carbon-13 nuclear magnetic resonance, high-resolution mass spectrometry, and single-crystal diffraction. The synthesized compounds exhibited excellent insecticidal activities against five species of aphids, including Schizaphis graminum, Brevicoryne brassicae, Aphis gossypii, Aphis citricola Van der, and Myzus persicae. The median lethal concentration values of the compound H-13 for S. graminum, B. brassicae, A. gossypii, A. citricola Van der, and M. persicae were 8.72, 13.77, 14.17, 12.96, and 12.35 μg/mL, respectively. The mode of action test results indicated that compound H-13 had superior contact and systemic activity against M. persicae, similar to the positive control flonicamid. Furthermore, a field trial showed that the control effect of compound H-13 at 100 μg/mL concentration was comparable to that of flonicamid against M. persicae. The mortality was 85.6% and 90.3% after 7 and 14 days, respectively. Finally, to further explore the action mechanism of these compounds, the insecticidal activity of compounds H-13 (strong) and H-24 (weak) on aphid protease was determined. Compound H-13 was found to have a significant inhibitory effect on the strong alkaline tryptase activity. Compound H-13 might cause aphid poisoning and death by inhibiting the trypsin activity. This study provided important insights for the discovery and development of new insecticides.

New daphnane diterpenoidal 1,3,4-oxdiazole derivatives as potential anti-hepatoma agents: Synthesis, biological evaluation and molecular modeling studies

Hepatocellular carcinoma (HCC) is a major challenge for human healthy. Daphnane-type diterpenes have attracted increasingly attention due to remarkable pharmaceutical potential including anti-HCC activity. To further develop this class of compounds as inhibitors of HCC, the daphnane diterpenoids 12-O-debenzoyl-Yuanhuacine (YHC) and 12-hydroxydaphnetoxin (YHE) were prepared by a standard chemical transformation from dried flower buds of the Daphne genkwa plant. Subsequently, 22 daphnane diterpenoidal 1,3,4-oxdiazole derivatives were rationally designed and synthesized based on YHC and YHE. The assessment of the target compound's anti-hepatocellular carcinoma activity revealed that YHC1 exhibited comparable activity to sorafenib in the Hep3B cell line, while demonstrating higher selectivity. The mechanistic investigation demonstrates that compound YHC1 induces cell cycle arrest at the G0/G1 phase, cellular senescence, apoptosis, and elevates cellular reactive oxygen species levels. Moreover, molecular docking and CETSA results confirm the interaction between YHC1 and YAP1 as well as TEAD1. Co-IP experiments further validated that YHC1 can effectively inhibit the binding of YAP1 and TEAD1. In conclusion, YHC1 selectively targets YAP1 and TEAD1, exhibiting its anti-hepatocellular carcinoma effects through the inhibition of their interaction.

Anti-inflammatory and Antimicrobial Potential of 1, 3, 4-oxadiazoles and its Derivatives: A Review

1, 3, 4-oxadiazole and its derivatives have significant anti-inflammatory and antimicrobial property. Their precise mechanism of action is not known but it is postulated that they act by inhibiting the biosynthesis of certain prostaglandins. 1, 3, 4-oxadiazoles are a class of heterocyclic compounds with wide variety of biological and pharmacological activities. They have been reported to possess analgesic, antimicrobial, antipyretic and anti-inflammatory properties. These compounds are also active against a number of other inflammatory conditions such as arthritis, gout etc. A wide variety of these compounds have been synthesized and some of them are under clinical trials. In this review article, anti-inflammatory and antimicrobial activity of the 1, 3, 4- oxadiazole shall be discussed.

Synthesis, Bioactivity and Molecular Docking of Nereistoxin Derivatives Containing Phosphonate

Novel nereistoxin derivatives containing phosphonate were synthesized and characterized via ³¹P, ¹H and ¹³C NMR and HRMS. The anticholinesterase activity of the synthesized compounds was evaluated on human acetylcholinesterase (AChE) using the in vitro Ellman method. Most of the compounds exhibited good inhibition of acetylcholinesterase. All of these compounds were selected to assess their insecticidal activity (in vivo) against Mythimna separata Walker, Myzus persicae Sulzer and Rhopalosiphum padi. Most of the tested compounds displayed potent insecticidal activity against these three species. Compound 7f displayed good activity against all three insect species, showing LC₅₀ values of 136.86 μg/mL for M. separata, 138.37 μg/mL for M. persicae and 131.64 μg/mL for R. padi. Compound 7b had the highest activity against M. persicae and R. padi, with LC₅₀ values of 42.93 μg/mL and 58.19 μg/mL, respectively. Docking studies were performed to speculate the possible binding sites of the compounds and explain the reasons for the activity of the compounds. The results showed that the compounds had lower binding energies with AChE than with the acetylcholine receptor (AchR), suggesting that compounds are more easily bound with AChE.

Identification of azukisapogenol triterpenoid saponins from Oxytropis hirta Bunge and their aphicidal activities against pea aphid Acyrthosiphon pisum Harris

BACKGROUND

Acyrthosiphon pisum Harris is the most destructive pest worldwide because of its ability to feed on plants directly and transmit plant viruses as a vector. This study aims to identify triterpenoid saponins from Oxytropis hirta Bunge as biopesticides to control aphids.

RESULTS

Three new azukisapogenol triterpenoid saponins (1-3), a new pinoresinol lignan glycoside (8), and four known saponins (4-7) were identified from the root of O. hirta. Compounds 4-7 displayed significant aphicidal activities against A. pisum with oral toxicities (LC₅₀  = 51.10-147.43 μg/mL, 72 h), deterrent effects (deterrence index = 1.00, 100-200 μg/mL, 24 h), and aphid reproduction inhibitory effects (inhibition rates = 75.91-86.73%, 400 μg/mL, 24 h), respectively. The carboxyl groups at C-3 GlcA and C-30 were functional groups for their aphicidal activities. The toxic symptoms caused by the optimal 5 involved insect body-color changes from light green to dark or gray-green, and then brown until death. The intestinal cavity, apical microvilli, nuclei, mitochondria, and electron dense granules in the midgut tissues of A. pisum were the target sites showing aphicidal activity. The suppression of pepsin and α-amylase, and the activation of lipase and trypsin could be the signs of organelle damage in the midgut tissues.

CONCLUSION

Azukisapogenol triterpenoid saponins from O. hirta could be used as biopesticides to control aphids for their multiple efficacies, including oral toxicity, deterrent activity, and reproduction inhibitory activity. The toxic symptoms involved insect body-color changes. Midgut tissues and their related enzymes were the targets for saponins showing aphicidal activities. © 2022 Society of Chemical Industry.

Synthesis of Piperine-Based Ester Derivatives with Diverse Aromatic Rings and Their Agricultural Bioactivities against Tetranychus cinnabarinus Boisduval, Aphis citricola Van der Goot, and Eriosoma lanigerum Hausmann

Exploration of plant secondary metabolites or by using them as leads for development of new pesticides has become one of the focal research topics nowadays. Herein, a series of new ester derivatives of piperine were prepared via the Vilsmeier−Haack−Arnold (VHA) reaction, and their structures were characterized by infrared spectroscopy (IR), melting point (mp), proton nuclear magnetic resonance spectroscopy (1H NMR), and carbon nuclear magnetic resonance spectroscopy (13C NMR). Notably, the steric configurations of compounds 6 and 7 were confirmed by single-crystal analysis. Against T. cinnabarinus, compounds 9 and 11 exhibited 47.6- and 45.4-fold more pronounced acaricidal activity than piperine. In particular, compounds 9 and 11 also showed 2.6-fold control efficiency on the fifth day of piperine. In addition, compound 6 (>10−fold higher than piperine) displayed the most potent aphicidal activity against A. citricola. Furthermore, some derivatives showed good aphicidal activities against E. lanigerum. Moreover, the effects of compounds on the cuticles of T. cinnabarinus were investigated by the scanning electron microscope (SEM) imaging method. This study will pave the way for future high value added application of piperine and its derivatives as botanical pesticides.

High Value-Added Application of Natural Plant Products in Crop Protection: Construction and Pesticidal Activities of Piperine-Type Ester Derivatives and Their Toxicology Study

To discover new potential pesticide candidates, recently, structural modification of natural bioactive products has received much attention. In this work, a series of new piperine-type ester derivatives were regio- and stereoselectively synthesized based on a natural alkaloid piperine isolated from Piper nigrum. Their structures were characterized by IR, mp, ¹H NMR (¹³C NMR), and high-resolution mass spectrometry (HRMS). Against Tetranychus cinnabarinus Boisduval (Acari: Tetranychidae), compounds 4e, 4f, 4u, and 4v displayed the most significant acaricidal activity with LC₅₀ values of 0.155, 0.117, 0.177, and 0.164 mg/mL, respectively. Particularly, compound 4f showed >120-fold higher acaricidal activity than piperine (LC₅₀: 14.198 mg/mL). Notably, the acaricidal activity of 4f was equivalent to that of the commercial acaricide spirodiclofen (LC₅₀: 0.115 mg/mL). Additionally, against Eriosoma lanigerum Hausmann (Hemiptera: Aphididae), compounds 4w and 4b' showed 1.8-fold aphicidal activity of piperine. Furthermore, via the scanning electron microscope (SEM) imaging method, the obvious destruction of the construction of the cuticle layer of 4f-treated T. cinnabarinus was observed. Compound 4f could be further studied as a lead acaricidal agent.

The Insecticidal Efficacy and Physiological Action Mechanism of a Novel Agent GC16 against Tetranychus pueraricola (Acari: Tetranychidae)

Simple Summary

Spider mite is major pest in agriculture and have developed resistance to commonly used pesticides. Therefore, it is urgent to discover new pesticides to control the pest. In order to provide alternatives for its management, we evaluated the effectiveness of a new agent GC16 against the spider mite Tetranychus pueraricola. Then, we preliminarily revealed the its acaricidal mechanism of action based on the damage of cuticle and organelles of mites. We confirmed that GC16 has a good controlling effect on T. pueraricola and it is not harmful to Picromerus lewisi and Harmonia axyridis. Our research provides not only an alternative pesticide for the management of spider mites, but also guidance for the application of GC16 in sustainable agriculture.

Abstract

Chemical control plays a crucial role in pest management but has to face challenges due to insect resistance. It is important to discover alternatives to traditional pesticides. The spider mite Tetranychus pueraricola (Ehara & Gotoh) (Acari: Tetranychidae) is a major agricultural pest that causes severe damage to many crops. GC16 is a new agent that consists of a mixture of Calcium chloride (CaCl₂) and lecithin. To explore the acaricidal effects and mode of action of GC16 against T. pueraricola, bioassays, cryogenic scanning electron microscopy (cryo-SEM) and transmission electron microscopy (TEM) were performed. GC16 had lethal effects on the eggs, larvae, nymphs, and adults of T. pueraricola, caused the mites to dehydrate and inactivate, and inhibited the development of eggs. GC16 displayed contact toxicity rather than stomach toxicity through the synergistic effects of CaCl₂ with lecithin. Cryo-SEM analysis revealed that GC16 damaged T. pueraricola by disordering the array of the cuticle layer crest. Mitochondrial abnormalities were detected by TEM in mites treated by GC16. Overall, GC16 had the controlling efficacy on T. pueraricola by cuticle penetration and mitochondria dysfunction and had no effects on Picromerus lewisi and Harmonia axyridis, indicating that GC16 is likely a new eco-friendly acaricide.

Synthesis of New Spiro-Cyclopropanes Prepared by Non-Stabilized Diazoalkane Exhibiting an Extremely High Insecticidal Activity

The synthesis of new insecticidal gem-dimethyspiro-cyclopropanes derived from pyrrolidine-2,3-dione have been described, and their biological effect against different insect species has been evaluated. The presented results demonstrate the excellent insecticidal activity of cyclopropane 5c against Aedes aegypti and Musca domestica. Cyclopropane 5c showed the quickest knockdown and the best killing against Aedes aegypti and Musca domestica compared to trans-chrysanthemic acid and pyrethrin. The biological results of the high insecticidal activity were confirmed by the results of docking. This is evident in the binding affinity obtained for cyclopropane 5c, indicating good binding with an important active amino acid residue of the 5FT3 protein.

Design, Synthesis, and Biological Evaluation of Novel Psoralen-Based 1,3,4-Oxadiazoles as Potent Fungicide Candidates Targeting Pyruvate Kinase

Pyruvate kinase (PK) has been considered as a promising fungicide target discovered in our previous studies. Natural compounds are important sources for discovery and development of new pesticides. To continue our ongoing studies on the discovery of novel PK-targeted fungicides, a series of novel psoralen derivatives including a 1,3,4-oxadiazole moiety were designed by a computer-aided pesticide molecular design method, synthesized, and evaluated for their fungicidal activity. The bioassay results indicated that compounds 11d, 11e, 11g, 11i, and 12a showed excellent in vitro fungicidal activity against Botrytis cinerea with EC₅₀ values of 4.8, 3.3, 6.3, 5.4, and 3.9 μg/mL, respectively. They were more active than the corresponding positive control YZK-C22 [3-(4-methyl-1,2,3-thiadiazol-5-yl)-6-(trichloromethyl)-[1,2,4]-triazolo-[3,4-b][1,3,4]-thiadiazole] (with an EC₅₀ value of 13.4 μg/mL). Compounds 11g and 11i displayed promising in vivo fungicidal activity against B. cinerea with 80 and 70% inhibition at a concentration of 200 μg/mL, respectively. They possessed much higher fungicidal activity than the positive control psoralen and comparable activity with the positive control pyrisoxazole. Enzymatic assays indicated that 11i showed good BcPK inhibition with an IC₅₀ value of 39.6 μmol/L, comparable to the positive control YZK-C22 (32.4 μmol/L). Molecular docking provided a possible binding mode of 11i in the BcPK active site. Our studies suggested that the psoralen-based 1,3,4-oxadiazole 11i could be used as a new fungicidal lead targeting PK for further structural optimization.