A new series of N-heterocycles including pyridazinone, oxadiazole, triazolopyridazinone, and triazole derivatives were synthesized from the acid hydrazide via its reaction with certain carbon electrophiles.

Continual application of synthetic insecticides in controlling mosquito larvae has resulted in several problems as build-up of mosquito resistance beside to negative impacts on human health and environment. Discovering new and affordable bio-insecticidal agents with high efficiency, cost effective and target specific become a crucial need. The current study assessed the larvicidal activity of eight methanolic algal extracts belong to three different algal divisions against the 3^rd larval instar of Culex pipiens L. (Diptera: Culicidae). Comparative studies showed that four species of red and green algal extracts exhibited good larvicidal activity. Galaxaura elongata and Jania rubens (Rhodophyta), Codium tomentosum and Ulva intestinales (Chlorophyta) showed higher larvicidal potencies than Padina boryana, Dictyota dichotoma, and Sargassum dentifolium (Phaeophyta) and Gelidium latifolium (Rhodophyta). The maximum level of toxicity was achieved by exposure to G. elongata extract with LC₅₀ (31.13 ppm), followed by C. tomentosum (69.85 ppm) then J. rubens (84.82 ppm) and U. intestinalis (97.54 ppm), while the lowest toxicity exhibited by G. latifolium (297.38 ppm) at 72 h post- treatment. The application of LC₅₀ values of G. elongate, J. rubens, C. tomentosum, and U. intestinalis extracts affected the activities of antioxidant enzymes viz. superoxide dismutase, catalase and glutathione peroxidase as oxidative stress markers. An increase of antioxidant enzymes activities was recorded. Therefore, a significant elimination of free radicals, causing toxic effects. Overall, this study casts light on the insecticidal activity of some algal extracts, suggesting the possibility of application of these bio- agents as novel and cost- effective larvicides.

Mosquitoes are unquestionably the most medic arthropod vectors of disease. Culex pipiens, usually defined as a common house mosquito, is a well-known carrier of several virus diseases. Crude ethanol extracts of different organs of Agratum houstonianum are tested with Culex pipiens Linnaeus (Diptera: Culicidae) to determine their larvicidal, antifeedant, and repellency effects. Alongside biochemical analysis, the activity of the AChE, ATPase, CarE, and CYP-450 is detected in the total hemolymph of the C. pipiens larvae to examine the enzymatic action on the way to explain their neurotoxic effect and mode of action. Through HPLC and GC–MS analysis of the phytochemical profile of A. houstonianum aerial parts is identified. The larvicidal activity of aerial parts; flower (AF), leaf (AL), and stem (AS) of A. houstonianum extracts are evaluated against the 3rd instar larvae of C. pipiens at 24-, 48- and 72-post-treatment. A. houstonianium AF, AL, and AS extracts influenced the mortality of larvae with LC50 values 259.79, 266.85, and 306.86 ppm, respectively after 24 h of application. The potency of AF and AL extracts was 1.69- and 1.25-folds than that of AS extract, respectively. A high repellency percentage was obtained by AF extract 89.10% at a dose of 3.60 mg/cm². A. houstonianium AF prevailed inhibition on acetylcholinesterase and decrease in carboxylesterase activity. Moreover, a significant increase in the ATPase levels and a decrease in cytochrome P-450 monooxegenase activity (− 36.60%) are detected. HPLC analysis prevailed chlorogenic and rosmarinic acid as the major phenolic acids in AL and AF, respectively. GC–MS analysis of A. houstonianum results in the identification of phytol as the major makeup. Precocene I and II were detected in AF. Linoleic, linolenic, and oleic acid were detected in comparable amounts in the studied organs. Overall, results suggest that the A. houstonianum flower extract (AF) exhibits significant repellent, antifeedant, and larvicidal activities.

The resistance of mosquitos to conventional insecticides created an urgent need for using alternative insecticides. In this study, the toxicity of the neonicotinoids (acetamiprid and thiamethoxam) was evaluated against the 3rd larval instar of Culex pipens. In the larvicidal assay, acetamiprid and thiamethoxam showed promising larvicidal activity against Cx. pipiens, with LC50 values of 0.0093 and 0.0305 ppm after 24 hrs, 0.0078 and 0.0206 ppm after 48 hrs and 0.0065 and 0.0137 ppm after 72 hrs of insecticidal exposure. The activity of acetylcholinesterase (AChE), carboxylesterase, (α-esterase), (β-esterase), and glutathione S- transferase (GST) were determined after 72 hrs of insecticidal exposure. Acetamiprid showed a significant increase in the activity level of AChE, GST, carboxylesterase, α, and β- esterases than thiamethoxam. The hemocytes of the treated 3rd larval instar of Cx. pipens were sensitive to both insecticides and showed remarkable deformation compared with control. Therefore, both detoxification enzymes and physiological resistance play a great role in neonicotinoids detoxification.

Mosquito control is a favorable strategy to prevent mosquito-borne diseases. There are various approaches for the management of potentially dreadful mosquito populations such as larvicides and adulticides. In this study, a series of novel benzochromene derivatives were synthesized and evaluated for their insecticidal efficacy against larvae and adult stages of Culex pipiens L. The synthesized compounds underwent comprehensive structural characterization and toxicological evaluation, revealing their larvicidal and adulticidal activity for several derivatives. The tested compounds were more effective against larvae than adults of C. pipiens . Compounds 10 and 5 exhibited pronounced larvicidal activity, surpassing the reference compound temephos, with LC₅₀ values of 40.15 and 46.17 ppm, respectively. In addition, both compounds displayed remarkable adulticidal efficacy, with LC₅₀ values of 55.02 and 65.43 ppm, respectively, whereas compound 6 showed the lowest potency among the tested series with LC₅₀ value of 215.40 ppm. Notably, compounds 10 and 5 were 5.36- and 4.66-fold more active against larvae than compound 6 , and demonstrated 5.28- and 4.44-fold higher adulticidal efficiency compared with deltamethrin. In cytotoxicity assays, compound 5 displayed an IC₅₀ value of 72.65 µM, while compound 10 showed an IC₅₀ of 90.32 µM, indicating low toxicity toward normal human cells and a favorable selectivity index. Molecular docking supported this observation by demonstrating strong and specific binding interactions with Anopheles gambiae acetylcholinesterase (AChE). Additionally, the DFT results provided insights into the electronic properties and stability of the compounds, while MEP mapping highlighted key reactive sites associated with target interactions. Structure–activity relationship (SAR) studies identified crucial functional groups influencing insecticidal potency.

The cowpea aphid, Aphis craccivora (Koch), is a significant agricultural pest that globally affects numerous crops, leading to substantial yield losses through both feeding and the transmission of viral diseases. Flupyradifurone has an excellent safety profile and a unique mode of action; resistance to flupyradifurone has been reported in certain aphid species. In the current study, the cross-resistance and resistance mechanisms of A. craccivora to flupyradifurone were investigated. The results revealed that A. craccivora developed a resistance ratio (RR) of 46.6-fold as a result of laboratory selection for 28 consecutive generations. In the flupyradifurone-resistant strain (R-strain), metabolic enzyme determinations indicated significant increases in cytochrome P450 monooxygenase, esterase, and glutathione S-transferase activities. Moreover, quantitative real-time PCR (RT-qPCR) revealed the differential expression of CYP6DA2 and CYP380C6, with CYP6DA2 being upregulated, suggesting its pivotal role in flupyradifurone resistance. Molecular docking studies demonstrated a stronger binding affinity of flupyradifurone to CYP6DA2 than to CYP380C6, further supporting its involvement in detoxification processes. The findings also highlighted moderate cross-resistance to malathion, underscoring the need for insecticide management to mitigate the evolution of resistance. This study provides critical insights into the biochemical mechanisms underlying flupyradifurone resistance in A. craccivora and emphasizes the importance of developing effective resistance management strategies for pest control.