Imidacloprid and Related Compounds: Structure and Water Solubility of N-Alkyl Derivatives of Imidacloprid

An intramolecular hydrogen bond between NH???O₂N in insecticide, imidacloprid (1), and its nitromethylene analog 15 was proved by NMR and IR spectra. That electron delocalization over their planar moieties was disrupted by alkylation at the imidazolidine nitrogen atom is demonstrated by the hypsochromic shifts in UV and deshielding effect in NMR spectra. Interestingly, the N-alkyl derivatives (C1-5) had greater water solubility than 1, although increasing alkyl chain length decreased the solubility. The hydrophilicity of the alkyl derivatives would result from remote charge heads being formed as a result of the conjugation disruption by alkylation, while the hydrophobicity of 1 could be ascribed to the charge distribution over the conjugated system coupled with the intramolecular H-bonding. The greater water solubility of 15 than 1 and contrastively small solubility of the cyanoimine analogue are discussed based on the difference in their steric crowding.     

抗吡虫啉单克隆抗体的制备及鉴定

为制备灵敏度高,特异性强的抗吡虫啉单克隆抗体,建立经济、快速、准确的吡虫啉残留免疫学分析方法,采用分子模拟技术分析吡虫啉及其类似农药的电荷分布后,选择1-[6-(2-羧乙硫基-3-吡啶)甲基]-N-硝基-2-咪唑啉亚胺 (H1) 作为免疫半抗原,1-(6-氯-3-吡啶甲基)-3-羧丙基-N-硝基-2-咪唑啉亚胺 (H2) 作为包被半抗原,利用NHS酯法将H1和H2分别与牛血清蛋白 (BSA) 和卵清蛋白 (OVA) 偶联合成免疫原与包被原。免疫BALB/c小鼠后,采用常规杂交瘤技术共获得2株稳定分泌抗吡虫     

亚致死剂量杀虫剂对意蜂工蜂嗅觉敏感性的影响

喙伸反应(PER)试验适用于评价杀虫剂对蜜蜂行为的影响。本实验利用喙伸反应研究了亚致死剂量(LD50/100～LD50/10)溴氰菊酯和吡虫啉对意蜂Apis mellifera ligustica L.工蜂嗅觉敏感性的影响。结果发现,经口饲喂溴氰菊酯5ng和10ng后,工蜂对0.1%的蔗糖溶液的敏感性显著下降(P<0.05),水应激指数降低,但对0.3%,1%,3%,10%和30%的蔗糖溶液的敏感性没有显著变化;而经口饲喂吡虫啉0.3ng和0.6ng后,工蜂对上述各浓度蔗糖溶液的敏感性变化不明显,但其水应激指数升高。     

Influence of Y151F mutation in loop B on the agonist potency in insect nicotinic acetylcholine receptor

Abstract  Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels, which mediate fast cholinergic synaptic transmission in insect and vertebrate nervous systems. The nAChR agonist-binding site is present at the interface of adjacent subunits and is formed by loops A–C present in α subunits together with loops D–F present in either non-α subunits or homomer-forming α subunits. Although Y151 in loop B has been identified as important in agonist binding, various residues at the 151-site are found among vertebrate and invertebrate nAChR α subunits, such as F151. In Xenopus oocytes expressing Nlα1 or Nlα1^Y151F plus rat β2, Y151F mutation was found to significantly change the rate of receptor desensitization and altered the pharmacological properties of acetylcholine, but not imidacloprid, including the decrease of I _max, the increase of EC₅₀ (the concentration causing 50% of the maximum response) and the fast time-constant of decay (τ_f). By comparisons of residue structure, the hydroxyl group in the side chain of Y151 was thought to be important in the interaction between Nlα1/β2 nAChRs and acetylcholine, and the phenyl group to be important between Nlα1/β2 nAChRs and imidacloprid.     

吡虫啉对白背飞虱抑食作用的初步研究

吡虫啉对白背飞虱取食的抑制作用可以用蜜露分泌量的减少和体重的减轻来衡量。吡虫啉处理后,白背飞虱蜜露分泌量的减少比率随浓度的加大而上升,随处理后时间的推移首先表现为上升,到达最大值后再下降,最高浓度0.0250mg/kg处理,蜜露分泌量减少最显著的第6d,减少比率为57.28%。与对照相比,吡虫啉处理后,白背飞虱体重的变化随浓度上升而加大,随时间的推移表现为持续上升,最高浓度0.0250mg/kg处理时,第8d的体重减轻比率为36.03%。     

Comparative efficacy of different pesticides against mango bark beetle Hypocryphalus mangiferae Stebbing (Coleoptera: Scolytidae)

Hypocryphalus mangiferae Stebbing is one of the most destructive insect pests of mango trees and is found to be associated with the transmission of causal organisms of mango sudden death disease. The present study was carried out to evaluate the toxicity of deltamethrin, bifenthrin, chlorpyrifos, emamectin benzoate, imidacloprid and spinosad in laboratory and field trials. Bioassay results showed that the toxicity of chlorpyrifos was significantly higher than deltamethrin but similar to bifenthrin. Deltamethrin and bifenthrin toxicity, however, increased significantly (P < 0.01) from day 1 to day 3. Spinosad was the least toxic compound while emamectin was the most toxic among new chemical insecticides tested, but its toxicity increased significantly from day 1 to day 5. Comparison of the efficacies of the insecticides using lethal times to produce 50% mortality (LT₅₀) and 90% mortality (LT₉₀) showed that the relative potencies of chlorpyrifos, emamectin, imidacloprid and spinosad were greater than bifenthrin and deltamethrin. The results of field trials showed the highest number of beetles emerged from the control twigs while significantly fewer beetles emerged from the twigs treated with bifenthrin (P < 0.05), which accounted for 12% for bifenthrin compared to that of the control. The present study demonstrated increased toxicities of systemic insecticides and chlorpyrifos compared to toxicities of deltamethrin and bifenthrin, suggesting these insecticides could be an alternative tool in a comprehensive H. mangiferae management program to eradicate the beetles from mango orchards.     

Insecticide resistance in Bemisia tabaci from Cyprus

Abstract A comprehensive study on the Bemisia tabaci (biotype B) resistance to neonicotinoid insecticides imidacloprid, acetamiprid and thiamethoxam, and pyrethroid bifenthrin was conducted in Cyprus. The resistance level to eight field‐collected B. tabaci populations was investigated. The activities of enzymes involved in metabolic detoxification and the frequencies of pyrethroid and organophosphates target site resistance mutations were determined. Moderate to high levels of resistance were detected for imidacloprid (resistance factor [RF] 77–392) and thiamethoxam (RF 50–164) while low resistance levels were observed for acetamiprid (RF 7–12). Uniform responses by the Cypriot whiteflies could be observed against all neonicotinoid insecticides. No cross‐resistance between the neonicotinoids was detected as well as no association with the activity of the P450 microsomal oxidases. Only imidacloprid resistance correlated with carboxylesterase activity. Low to extremely high resistance was observed for insecticide bifenthrin (RF 49–1 243) which was associated with the frequency of the resistant allele in the sodium channel gene but not with the activity of the detoxification enzymes. Finally, the F331W mutation in the acetylcholinesterase enzyme ace1 gene was fixed in all B. tabaci populations from Cyprus.