Larvicidal activity of Cnidium monnieri fruit coumarins and structurally related compounds against insecticide-susceptible and insecticide-resistant Culex pipiens pallens and Aedes aegypti

BACKGROUND: An assessment was made of the toxicity of imperatorin and osthole identified in Cnidium monnieri fruit, 11 related compounds and five insecticides to larvae from insecticide‐susceptible Culex pipiens pallens (KS‐CP strain) and Aedes aegypti and wild C.p. pallens (YS‐CP colony) using a direct‐contact mortality bioassay. Results were compared with those of the conventional larvicide temephos. RESULTS: Imperatorin (LC₅₀ = 3.14 and 2.88 mg L^?1) was 1.9‐, 3.7‐ and 4.2‐fold and 2.4‐, 4.5‐ and 4.6‐fold more toxic than isopimpinellin, isoimperatorin and osthole against susceptible C. p. pallens and A. aegypti larvae respectively. Overall, all of the compounds were less toxic than temephos (0.011 and 0.019 mg L^?1). The toxicity of these compounds was virtually identical against larvae from the two Culex strains, even though YS‐CP larvae were resistant to fenthion (resistance ratio RR = 390), deltamethrin (RR = 164), cyfluthrin (RR = 14) and temephos (RR = 14). This finding indicates that the coumarins and the insecticides do not share a common mode of action. The structure–activity relationship indicates that the chemical structure and alkoxy substitution and length of the alkoxyl side chain at the C8 position are essential for imparting toxicity. CONCLUSION: The C. monnieri fruit‐derived coumarins and the related coumarins described merit further study as potential insecticides or lead molecules for the control of insecticide‐resistant mosquito populations. Copyright © 2012 Society of Chemical Industry     

五种伞形科中草药乙醇提取物对淡色库蚊的控制作用

研究了5种伞形科植物蛇床、防风、当归、紫花前胡和白芷对淡色库蚊幼虫和成虫的生物活性，采用浸渍法测定了样品乙醇提取物对蚊幼虫的杀伤作用，采用三角瓶法测定了样品乙醇提取物对蚊成虫的熏蒸作用。结果表明，5种伞形科中草药的乙醇粗提物对淡色库蚊幼虫和成虫的杀伤效应不同：蛇床子的乙醇粗提物对淡色库蚊幼虫的毒杀效果最佳（24h的LC90为49．886mg／L），白芷的乙醇粗提物对淡色库蚊成虫的熏蒸效果最佳（KT90为23．271min）。     

球形芽孢杆菌Ts—1对十种蚊幼虫毒效测定

用球形芽孢杆菌Ts—1冻干菌粉,对国内10种蚊幼虫生物测定的结果表明,不同蚊种之间敏感性有很大差异。库蚊属蚊虫(特别是淡色库蚊和致倦库蚊)对Ts—1敏感性很高,按蚊其次,而伊蚊属除东乡伊蚊外对Ts—1均不敏感。此外,同一蚊种不同地理株之间,对Ts一1的敏感性也有显著差异。     

八种蚊幼虫对苏云金杆菌H-14的敏感性测定

进行了苏云金杆菌H—14对我国8种重要病媒蚊种,即3株埃及伊蚊、6株白纹伊蚊、黄斑伊蚊、淡色库蚊、致倦库蚊、三带喙库蚊、中华按蚊及嗜人按蚊的幼虫的毒力测定,从24小时结果可看出,淡色库蚊最敏感,其次是白纹伊蚊的宜兴株和广东海南株,LC_(50)分别为52.5,57.0和64.5国际毒力单位/立升水,最不敏感的是嗜人按蚊和中华按蚊。对嗜人按蚊24小时LC_(50)约为48小时的5倍,别的蚊种则的为2倍。     

细辛醚对家蝇和淡色库蚊的生物活性

为了进一步确定细辛醚的作用谱和作用方式,测定了其对家蝇和淡色库蚊的触杀、熏蒸和忌避活性。结果表明:细辛醚对家蝇4 h的触杀LD50值为3.45 μg/头;对家蝇、淡色库蚊4 h的熏蒸LC50值分别为5.77和4.24 μL/L;对两者在LC80剂量下熏蒸处理的击倒中时(KT50)值分别为11.64和4.80 min;在1 mg/mL的浓度下,对家蝇的忌避率为81.82%。中毒家蝇依次表现出兴奋、痉挛、麻痹和死亡等症状。     

Insecticidal properties of essential plant oils against the mosquito Culex pipiens molestus (Diptera: Culicidae)

The insecticidal activities of essential oil extracts from leaves and flowers of aromatic plants against fourth-instar larvae of the mosquito Culex pipiens molestus Forskal were determined. Extracts of Myrtus communis L were found to be the most toxic, followed by those of Origanum syriacum L, Mentha microcorphylla Koch, Pistacia lentiscus L and Lavandula stoechas L with LC50 values of 16, 36, 39, 70 and 89 mg litre-1, respectively. Over 20 major components were identified in extracts from each plant species. Eight pure components (1,8-cineole, menthone, linalool, terpineol, carvacrol, thymol, (1S)-(-)-alpha-pinene and (1R)-(+)-alpha-pinene) were tested against the larvae. Thymol, carvacrol, (1R)-(+)-alpha-pinene and (1S)-(-)-alpha-pinene were the most toxic (LC50 = 36-49 mg litre-1), while menthone, 1,8-cineole, linalool and terpineol (LC50 = 156-194 mg litre-1) were less toxic.     

Repellency and toxicity of aromatic plant extracts against the mosquito Culex pipiens molestus (Diptera: Culicidae)

The insecticidal activities of essential oil extracts from leaves, flowers and roots of aromatic plants against fourth-instar larvae of the mosquito Culex pipiens molestus Forskal were determined. Extracts of Foeniculum vulgare Mill were the most toxic, followed by those of Ferula hermonis Boiss, Citrus sinensis Osbeck, Pinus pinea L, Laurus nobilis L and Eucalyptus spp with LC50 values of 24.5, 44.0, 60.0, 75.0, 117.0 and 120.0 mg litre(-1), respectively. Combination tests between the LC50 and the maximum sub-lethal concentration (MSLC) were determined. Over 20 major components were identified in extracts from each plant species tested. Five essential oils and nine pure components were studied for their repellency against mosquito bites. Terpineol and 1,8-cineole were the most effective against Culex pipiens molestus bites offering complete protection for 1.6 and 2 h, respectively.     

Chitin synthesis inhibitor effect on Aedes aegypti populations susceptible and resistant to organophosphate temephos

BACKGROUND: In Brazil, dengue vector control is hampered by the resistance of Aedes aegypti L. populations to organophosphates (OPs). Insect growth regulators (IGRs) are a promising alternative, as their mechanisms of action are different from those of conventional insecticides. The authors analysed the effect of the IGR triflumuron, a chitin synthesis inhibitor, on the Ae. aegypti insecticide-susceptible strain Rockefeller, as well as on field populations both susceptible (TemS) and resistant (TemR) to the OP temephos. RESULTS: Triflumuron arrested development and inhibited adult emergence of the Rockefeller strain in a dose-dependent way (EI(50) and EI(90) of 0.8 and 1.8 microg L(-1) respectively). A direct relationship between triflumuron concentration and the precocity of its effects was evident. TemS and TemR temephos resistance ratios (RR(90)) were 4.5 and 13.8, triflumuron RR(90) being 1.0 and 1.3 respectively. CONCLUSION: The IGR triflumuron exhibited a dose-dependent effect against the reference Ae. aegypti Rockefeller strain. It was also effective against two field populations, regardless of their OP resistance status. The present results are discussed in the context of utilization of chitin synthesis inhibitors as potential alternatives in the control of Ae. aegypti in Brazil.     

氟铃脲对韭菜迟眼蕈蚊不同虫态的致毒特点及毒力

为明确氟铃脲对韭菜迟眼蕈蚊不同虫态的致毒特点及毒力,采用胃毒触杀联合毒力法、药液定量滴加法及药膜法分别对韭菜迟眼蕈蚊卵、幼虫、蛹、成虫进行了生物测定。结果表明,经氟铃脲处理的0.5~1、1.5~2和2.5~3日龄韭菜迟眼蕈蚊卵至孵化24 h后,LC_(50)依次为2.27、1.60和0.64 mg/L,对1.5~3日龄卵的毒力高于对0.5~1日龄卵;经氟铃脲处理的2日龄卵、2龄幼虫、4龄幼虫、1日龄和3日龄蛹至羽化时LC_(50)分别为0.06、0.30、0.34、24.05和27.42 mg/L,毒力程度随韭菜迟眼蕈蚊发育而逐步下降;对蛹和成虫毒力较低,100 mg/L氟铃脲染毒1、3日龄蛹的羽化率分别高于10%和20%;药膜法100、1 000 mg/L氟铃脲处理成虫24 h,校正死亡率低于20%。研究表明,氟铃脲对韭菜迟眼蕈蚊各虫态的生长发育均有不利影响,抑制卵的孵化并导致初孵幼虫存活率降低;对幼虫毒杀作用较慢,对蛹及成虫阶段毒力较低。     

Isolation of a Pseudomonas fluorescens metabolite/exotoxin active against both larvae and pupae of vector mosquitoes

A formulation was developed from the metabolite(s) of a novel Pseudomonas fluorescens Migula strain (VCRC B426) and tested against 4th-instar larvae and pupae of three species of vector mosquitoes, Anopheles stephensi Liston, Culex quinquefasciatus Say and Aedes aegypti (L). The larvae and pupae of An. stephensi were the most susceptible to the formulation, followed by those of C. quinquefasciatus and Ae. aegypti, in that order, and the dosage requirement for pupal mortality was less than that required for larval mortality. The LC50 dosage requirements for larvae of these mosquito species were, respectively, 70.4, 511.5 and 757.3 microg protein ml(-1), whereas for pupae they were, respectively, 2.0, 9.4 and 19.2 microg protein ml(-1). The lethal fraction was purified from the culture broth and its molecular mass, as determined by high performance liquid chromatography, was 44kDa. This is the first report of a microbial formulation acting upon mosquito pupae, a non-feeding stage. Its mode of action and efficacy to control mosquitoes under field conditions need to be studied further.     

对氯苯丙酮肟衍生物的合成及其生物活性

为寻找新型结构的农药先导化合物,采用1-对氯苯基-3-氯-1-丙酮为原料,合成了14个结构新颖的对氯苯丙酮肟衍生物,其化学结构经1H核磁共振和元素分析确证。初步的生物活性试验结果表明,该类化合物具有一定的杀虫和除草活性,其中化合物 Ⅴi、Ⅴe和Ⅴh 在 50 mg/L浓度下对淡色库蚊Culex pipiens pallens的致死率达到100%。     

Development of biodegradable aluminium carboxymethylcellulose matrices for mosquito larvicides

The use of ecofriendly biodegradable controlled-release formulations of mosquito larvicides could reduce the frequency of application and losses due to degradation of the insecticide compared with conventional formulations. Among the 20 matrices developed by entrapping the organophosphorus mosquito larvicide, fenthion, in carboxymethylcellulose ionotropically cross-linked with aluminium ions which were studied for release profiles, two matrices, CRF3b and CRF5b, were found to be stable for 16 and 14 weeks under simulated field conditions. The average concentration of fenthion released per week ranged from 0.06 to 3.5 mg litre(-1) for CRF3b and 0.09 to 2.72 mg litre(-1) for CRF5b. Of these two formulations, CRF3b was the more stable, maintaining the concentration of the active ingredient at the level required to effect mosquito control. The cumulative release of fenthion per pellet was 80% from CRF3b and 72% from CRF5b. Based on the study with fenthion, two similar matrices for triflumuron, a benzoylphenylurea insect growth regulator, STAR3b and STAR5b were developed. These matrices were stable up to 16 weeks with the average concentration of triflumuron released per week ranging from 0.05 to 3.44 mg litre(-1) for STAR3b and 0.07 to 2.71 mg litre(-1) for STARSb. The cumulative release of triflumuron per pellet was 75% from STAR3b and 76% from STAR5b. From the results of this study under simulated conditions, it is estimated that the application of four pellets of either fenthion or triflumuron per square metre of the breeding surface may play a useful role in controlling Culex quinquefasciatus Say in larval habitats for about 4 months.     

Effects of N-acetylcysteine on oxidative responses in the liver of fenthion exposed Cyprinus carpio

The aim of this study was to evaluate the effects of different N-acetylcysteine doses on the tolerance to fenthion-induced oxidative stress, alterations in glutathione metabolism and cholinesterase specific activities in the liver by using freshwater fish Cyprinus carpio (Cyprinidae) as a model organism. An acute toxicity study was carried out to determine 96-h median lethal concentration of fenthion for this species (2.16 mg/L) and 80% of this concentration was applied in toxicity studies. Four groups, each containing eight fish were constituted as follows: Control group, fenthion treated group, 0.5 or 400 mg/kg NAC-injected + fenthion-treated groups. Biochemical analyses were carried out spectrophotometrically. Fenthion treatment significantly decreased total glutathione and glutathione levels, glutathione/glutathione disulfide ratio together with glutathione reductase and γ-glutamylcysteine synthetase specific enzyme activities. The higher dose of N-acetylcysteine increased the toxic effects of fenthion and γ-glutamyl transpeptidase specific activity while decreasing glutathione S-transferase specific activity. However, injection of the lower dose provided a limited protection against fenthion toxicity. In all exposure groups, lipid peroxidation increased and total protein levels decreased, while protein depletion was prevented by low dose of N-acetylcysteine application. Acetylcholinesterase and butyrylcholinesterase activities were at similar levels in the liver of C. carpio. A dose-dependent inhibition was observed in butyrylcholinesterase activity by N-acetylcysteine application. The results showed that fenthion had a significant oxidative stress inducing potential through the reduction of glutathione redox capacity. The critical point for overcoming oxidative stress by N-acetylcysteine in fenthion toxicity was the selection of the dose; N-acetylcysteine exerted its toxic effects by means of oxidative stress in fish liver at the higher dose.     

含1,4-二氢吡啶环的新烟碱类化合物的合成及杀虫活性

通过NTN32692、芳香醛和氰基乙酸乙酯参与的多组份反应合成了15个全新的含1,4-二氢吡啶环的新烟碱类化合物,其结构均经过核磁共振氢谱、高分辨质谱、红外光谱确证。室内生物测定结果表明,目标化合物对孑孓Culex pipiens pallens、粘虫Pseudaletia separate Walker和蚜虫Aphis craccivora具有较高的杀虫活性,部分化合物在质量浓度为500 mg/L下对粘虫和蚜虫的致死率可达到100%。     

新型腙类衍生物的合成及其生物活性

利用3-(N-甲基-N-甲氧基氨基)-1-芳基-1-丙酮腙与酰氯反应,合成了14个新型N-酰基-3-(N-甲基-N-甲氧基氨基)-1-芳基-1-丙酮腙化合物,其化学结构经1H核磁共振和元素分析确证。初步的生物活性测试结果表明,部分化合物在50 mg/L时对淡色库蚊Culex pipiens pallens的致死率为95%~100%;化合物 c7 在1 000 mg/L时对粘虫Leucania separata Walke 的致死率达100%。     

N-酰基苯并噁唑啉酮类化合物的合成及其生物活性

采用邻氨基酚为原料合成了N-酰基苯并噁唑啉酮类化合物30个,其化学结构经1H NMR及元素分析确证。初步的生物活性试验结果表明,该类化合物具有一定的杀虫、杀菌活性,其中化合物 3b、4b、14b、19b 在50 mg/L浓度下对淡色库蚊Culex pipiens pallens 的致死率为100%,有7个化合物在1 000 mg/L浓度下对朱砂叶螨Tetranychus cennbarinus的致死率达95%以上。     

N-酰基苯并噁唑啉酮类化合物的合成及其生物活性

采用邻氨基酚为原料合成了N-酰基苯并口恶唑啉酮类化合物30个,其化学结构经1H NMR及元素分析确证。初步的生物活性试验结果表明,该类化合物具有一定的杀虫、杀菌活性,其中化合物3b、4b、14b、19b在50mg/L浓度下对淡色库蚊Culex pipiens pallens的致死率为100%,有7个化合物在1 000mg/L浓度下对朱砂叶螨Tetranychus cennbarinus的致死率达95%以上。     

α-三联噻吩对淡色库蚊血细胞的光敏作用研究

研究了α-三联噻吩(α-T)对淡色库蚊Culex pipiens pallens幼虫血细胞的光敏作用。结果表明,在活体和离体条件下,α-T对淡色库蚊4种主要血细胞的形态延展及增殖均有不同程度的影响,处理后较短的时间内,α-T能促进血细胞的增殖,但随着作用时间的延长,其对血细胞均表现出抑制作用,且抑制程度随α-T浓度升高而逐渐增强。α-T对淡色库蚊不同血细胞的影响具有一定的差异,在处理早期,其对浆血胞(SP)和原血胞(PR)的增殖促进作用较强,而在处理后期,其对粒血胞(GR)和珠血胞(SP)的抑制作用较强,并且改变了淡色库蚊幼虫体内不同血细胞之间的比例,使得GR和SP所占比例逐渐降低。实验还表明,α-T对各种离体血细胞增殖的促进作用均较对活体的弱,且促进时间明显缩短。     

毒死蜱微球和乳油在水中的消解动态及其对白纹伊蚊幼虫的毒力

室内条件下,研究了不同浓度毒死蜱微球和毒死蜱乳油在水中的消解动态及其对白纹伊蚊Aedes albopictus 3龄幼虫的持续毒杀作用。结果表明:毒死蜱微球在水中的消解速率比乳油慢,半 衰期比乳油的长,高浓度微球和乳油的消解半衰期均长于低浓度下的消解半衰期。有效成分为1.2、 12和24 mg/L的毒死蜱微球和毒死蜱乳油在水中的消解半衰期分别为(19.4±2.1) d、(27.8±1.6) d、(31.0±1.7) d和(12.8±1.0) d、(16.1±0.9) d、(19.7±1.1) d;毒死蜱微球对白纹伊蚊3龄幼虫的毒杀作用强于乳油且持效期长,1.2 mg/L的毒死蜱微球水解85 d后处理白纹伊蚊3龄幼虫的死亡率高达76.6%,高于相同浓度、相同条件乳油的处理(53.3%),具有良好的持效性。     

Laboratory and field evaluations of rhodojaponin-III against the imported cabbage worm Pieris rapae (L.) (Lepidoptera: Pieridae)

The activity of rhodojaponin-III (R-III), a grayanoid diterpene compound isolated from Rhododendron molle G. Don flowers, was determined under laboratory and field conditions as an antifeedant, stomach poison, contact toxicant and insect growth inhibitor against Pieris rapae (L.) larvae. The median antifeedant concentration (AFC(50)) values in no-choice leaf disc tests were 1.16 and 15.85 mg L(-1) at 24 h after treatment when tested against third and fifth instars respectively. The median lethal concentration (LC(50)) values in leaf disc tests were 2.84 and 9.53 mg L(-1) at 96 h after treatment against third and fifth instars respectively. R-III showed an almost 30 times higher contact toxicity against third instars than for fifth instars, and the median lethal dose (LD(50)) values for topical application were 1.18 and 34.09 mg kg(-1) at 72 h after treatment respectively. R-III disrupted the development of larvae to pupae or adults with median concentration for inhibiting growth (IC(50)) values of only 1.36 mg L(-1) for third instars and 11.28 mg L(-1) for fifth instars. In field trials, a greater than 80% reduction in the adjusted larval numbers was obtained against P. rapae 14 days after treatment when Rhodo 0.1% EC, a commercial botanical insecticide based on R-III, was applied at both 937.5 and 625 mL ha(-1). These results suggest that further research to develop R-III, and extracts from R. molle, as biorational pesticides or as lead compounds for integrated pest management deserve consideration.