Synthesis, insecticidal evaluation and mode of action of novel anthranilic diamide derivatives containing sulfur moiety as potential ryanodine receptor activators

Toxicity and Sublethal Effects of Diamide Insecticides on Key Non-Target Natural Predators, the Larvae of Coccinella septempunctata L. (Coleoptera: Coccinellidae)

Coccinella septempunctata (ladybird) is an extremely important natural predator that feeds on aphids. An assessment of the toxicity of pesticides on environmental organisms is an essential component of Integrated Pest Management (IPM) strategies. This study evaluated diamide insecticides' toxicity at lethal and 30% lethal doses (LR₃₀) against C. septempunctata larvae. The pre-imaginal median lethal doses (LR₅₀) of chlorantraniliprole 10% SC, tetrachlorantraniliprole 10% SC, and broflanilide 10% SC were calculated to be 42.078, 289.516, and 0.0943 g active ingredient (a.i.)/ha, respectively. The mortality tests demonstrated that chlorantraniliprole and tetrachlorantraniliprole are comparatively less toxic to C. septempunctata than broflanilide, which were detected to be highly toxic to C. septempunctata. The mortality rates of the groups treated with the three diamide insecticides tended to stabilize after 96 h, extending to the pre-imaginal stage. Furthermore, when compared to broflanilide, which had a much higher potential risk, the hazard quotient (HQ) values indicated that chlorantraniliprole and tetrachlorantraniliprole have a lower risk potential for C. septempunctata in farmland and off farmland. The LR₃₀ dose induces abnormalities in the development phase 4th-instar larvae weight, pupal weight, and adult weight of treated C. septempunctata. The study emphasizes the importance of assessing the adverse effects of diamide insecticides on natural predator species that serve as biological control agents in agricultural IPM strategies.

3D-QSAR-Based Molecular Design to Discover Ultrahigh Active N-Phenylpyrazoles as Insecticide Candidates

Three-dimensional quantitative structure-activity relationship (3D-QSAR) is one of the most important and effective tools to direct molecular design in new pesticide development. Chlorantraniliprole is an anthranilic diamide ryanodine receptor (RyR) agonist with ultrahigh activity, high selectivity, and mammalian safety. To continue our studies on new insecticide development, here, we designed new insecticidal N-phenylpyrazoles by using 3D-QSAR of chlorantraniliprole analogues as a guide. Most of the target compounds synthesized exhibited medium to excellent activity against Mythimna separata, Plutella xylostella, and Spodoptera frugiperda. Compounds III b and III y showed similar activity against M. separata as chlorantraniliprole (LC₅₀ values: 0.21, 0.25, and 0.16 μg mL^-1 respectively). Compounds III b exhibited a 3-fold higher potency against P. xylostella than chlorantraniliprole. For S. frugiperda, the potency of III a and III b was 2.9 and 2.0 times higher than that of the positive control, respectively. The mode of action of the title compounds was validated by calcium imaging experiments and molecular docking using their target RyRs. III b can dock well with mutated P. xylostella RyRs, implying a potentially lower cross-resistance risk as compared with commercial RyR agonists. Density functional theory calculations suggested the feasibility of higher potency with the structural modifications. Compound III b was found to be an ultrahigh active insecticidal candidate with a broad spectrum for integrated pest management.

Comprehensive Overview of Diamide Derivatives Acting as Ryanodine Receptor Activators

The world's hunger is continuously rising due to conflicts, climate change, pandemics (such as the recent COVID-19), and crop pests and diseases. It is widely accepted that zero hunger is impossible without using agrochemicals to control crop pests and diseases. Diamide insecticides are one of the widely used green insecticides developed in recent years and play important roles in controlling lepidopteran pests. Currently, eight diamine insecticides have been commercialized, which target the insect ryanodine receptors. This review summarizes the development and optimization processes of diamide derivatives acting as ryanodine receptor activators. The review also discusses pest resistance to diamide derivatives and possible solutions to overcome the limitations posed by the resistance. Thus, with reference to structural biology, this study provides an impetus for designing and developing diamide insecticides with improved insecticidal activities.

Allicin-Inspired Heterocyclic Disulfides as Novel Antimicrobial Agents

In this work, a series of derivatives with disulfide bonds containing pyridine, pyrimidine, thiophene, thiazole, benzothiazole, and quinoline were designed and synthesized based on the various biological activities of allicin disulfide bond functional groups. The antimicrobial activities of the target compounds were determined, and the structure-activity relationships were discussed. Among them, compound S8 demonstrated the most potent antifungal activity in vitro against Monilinia fructicola (M. fructicola), with an EC₅₀ value of 5.92 μg/mL. Furthermore, an in vivo bioassay revealed that compound S8 exhibited equivalent curative and higher protective effects as the positive drug thiophanate methyl at a concentration of 200 μg/mL. The preliminary mechanism experiments showed that compound S8 could inhibit the growth of M. fructicola' s hyphae in a time- and concentration-dependent manner, and compound S8 could induce the shrinkage of hyphae, disrupt the integrity of the plasma membrane, and cause the damage and leakage of cell contents. More than that, compound S5 also demonstrated an excellent antibacterial effect on Xanthomonas oryzae (X. oryzae), with a MIC₉₀ value of 1.56 μg/mL, which was superior to the positive control, thiodiazole copper.

Discovery of a polysubstituted phenyl containing novel N-phenylpyrazole scaffold as potent ryanodine receptor activator

To develop the novel ryanodine receptors (RyRs) insecticides, encouraged by our previous research work, a series of novel N-phenylpyrazole derivatives containing a polysubstituted phenyl ring scaffold were designed and synthesized. The bioassays results indicated that some title compounds exhibited excellent insecticidal activity. For oriental armyworm (Mythimna separata), compounds 7f, 7g, 7i and 7o at 0.5 mg L^-1 displayed 100% larvicidal activity, and even at 0.1 mg L^-1, 7o was 30% larvicidal activity, comparable to chlorantraniliprole (30%) and better than cyantraniliprole (10%). Compounds 7f and 7o had the median lethal concentrations (LC₅₀) of 8.83 × 10^-2 and 7.12 × 10^-2 mg L^-1, respectively, close to chlorantraniliprole (6.79 × 10^-2 mg L^-1). Additionally, for diamondback moth (Plutella xylostella), the larvicidal activity of compounds 7f and 7i were 90% and 70% at 0.01 mg L^-1, respectively, better than chlorantraniliprole (50%) and cyantraniliprole (40%). More impressively, the LC₅₀ value of 7f was 4.2 × 10^-3 mg L^-1, slightly lower than that of chlorantraniliprole (5.0 × 10^-3 mg L^-1). The molecular docking between compound 7f and RyRs of diamondback moth validated our molecular designation. Furthermore, the calcium imaging experiment explored the influence of compound 7o on the calcium homeostasis in the central neurons of the third larvae of oriental armyworm. The results of this study indicated that 7o is a potent novel lead targeting at RyRs.

Synthesis, biological activities, and SAR studies of novel 1-(2-chloro-4,5-difluorophenyl)-1H-pyrazole derivatives

In order to search for the new ryanodine receptor (RyR) regulator, a series of 35 novel fluoro-substituted compounds introduced 1-(2-chloro-4,5-difluorophenyl)-1H-pyrazole moiety containing modified pyrazole heterocycle were designed and synthesized. Then, they were tested for the insecticidal activities against Mythimna separata and Plutella xylostella in our greenhouse. After a systematic biological screening, it was found out that IVc showed 50% larvicidal activities against Mythimna separata at 0.1 mg L^-1, equivalent to that of chlorantraniliprole (36%, 0.1 mg L^-1). The activity of IVc against Plutella xylostella was 90% at 10^-5 mg L^-1, whereas the chlorantraniliprole was 70% at the same concentration. Then, insect electrophysiology experiments were conducted to study the pattern of action of IVc and IVe. It was confirmed by the experimental results that both compounds could lead to the release of calcium from the endoplasmic reticulum of neurons as classical anthranilic diamide insecticides.