A piperidine amide extracted from Piper longum L. fruit shows activity against Aedes aegypti mosquito larvae

Mosquito larvicidal activity of Piper longum fruit-derived materials against the fourth-instar larvae of Aedes aegypti was examined. A crude methanol extract of P. longum fruits was found to be active against the larvae, and the hexane fraction of the methanol extract showed a strong larvicidal activity of 100% mortality. The biologically active component of P. longum fruits was characterized as pipernonaline by spectroscopic analyses. The LC(50) value of pipernonaline was 0.25 mg/L. The toxicity of pipernonaline is comparable to that of pirimiphos-methyl as a mosquito larvicide. In tests with available components derived from P. longum, no activity was observed with piperettine, piperine, or piperlongumine.     

Characteristics of maize flour tortilla supplemented with ground Tenebrio molitor larvae.

The larva of the Tenebrio molitor, known as the yellow meal worm, is a plague of wheat and flours. Consumption of the raw insects is not well accepted because of their appearance. The objective of the present work was to grow T. molitor larvae under standard conditions, to analyze the chemical composition of the larvae powder, and to prepare supplemented maize tortillas. Protein and fat contents were performed with standard methods. Tenebrio larvae powder had a 58.4% protein content; this protein was rich in essential amino acids such as phenylalanine, tyrosine, and tryptophan; the found values satisfied those recommended by the Food and Agriculture Organization. Fatty acid composition was determined by GC-MS showing high contents of oleic acid and linoleic acid (19.8 and 8.51%, respectively). A large proportion of unsaturated fatty acids of longer chains was detected. Long-chain fatty acids having two or three double bonds have been claimed as highly beneficial to health. Tortillas supplemented with larvae powder had excellent consumer acceptance, and tortilla protein content increased by 2% as well as the amount of essential amino acids. These results show new ways to consume insects and at the same time increase the nutritional value of the original food products.     

Larvicidal activity of lignans identified in Phryma leptostachya Var. asiatica roots against three mosquito species

The insecticidal activity of phytochemicals isolated from the roots of Phryma leptostachya var. asiatica against third instar larvae of Culex pipiens pallens, Aedes aegypti, and Ocheratatos togoi was examined. The two constituents of P. leptostachya var. asiatica roots were identified as the leptostachyol acetate (I) and 8'-acetoxy-2,2',6-trimethoxy-3,4,4',5'-dimethylenedioxyphenyl-7,7'-dioxabicyclo[3.3.0]octane (II) by spectroscopic analysis. Compound I was lethal to C. pipiens pallens, A. aegypti, and O. togoi at 10 ppm. Compound II showed weak or no insecticidal activity against three mosquito species at 10 ppm. The LC(50) values of I against C. pipiens pallens, A. aegypti, and O. togoi were 0.41, 2.1, and 2.3 ppm, respectively. Naturally occurring P. leptostachya var. asiatica root-derived compounds merit further study as potential mosquito larval control agents or lead compounds.     

New mosquito larvicidal tetranortriterpenoids from Turraea wakefieldii and Turraea floribunda

The crude methanol extracts of the root barks of Turraea wakefieldii and Turraea floribunda were found to show mosquito larvicidal activity against third-instar larvae of Anopheles gambiae sensu stricto. Four new limonoids comprising a vilasininoid 1 and three havanensinoids 2-4 were isolated from the chloroform fractions of the methanol extracts of T. wakefieldii and T. floribunda, respectively. The structures of the compounds were elucidated by NMR spectroscopy. Compounds 1, 2, and 4 had LD50 values of 7.1, 4.0, and 3.6 ppm, respectively, and were more potent than azadirachtin, which had an LD50 value of 57.1 ppm when tested against larvae of A. gambiae.     

Effects of teflubenzuron on larvae and juveniles of the polychaete Capitella SP. B from Barcelona, Spain

The insecticide teflubenzuron is currently employed by salmon farms as an in-feed compound to control ectoparasite infestations, and its occurrence in the sediments surrounding the farms could thus pose a hazard to local infauna. The effect of teflubenzuron on mortality, growth and metamorphosis of larvae of cultured Capitella sp. B were investigated. This is a poecilogonic species with two hatching periods. Larvae and juveniles produced during the first and second releases were exposed to sediment spiked with teflubenzuron (0, 8.4, 25 and 41.8 μg/g dry wt sediment) for a 31 days period and daily observations were performed. Teflubenzuron incorporated to sediment produced larval and juvenile mortality and a strong reduction of body size from juveniles of the two release periods. Larval metamorphosis was delayed without a clear dose-response relationship. This preliminary study suggests that teflubenzuron is harmful to early developmental stages of Capitella sp. B. This fact has relevant ecological effects such as a delay in recruitment of individuals into natural populations.     

Larvicidal activity of isobutylamides identified in Piper nigrum fruits against three mosquito species

The insecticidal activity of materials derived from the fruits of Piper nigrum against third instar larvae of Culex pipiens pallens, Aedes aegypti, and A. togoi was examined and compared with that of commercially available piperine, a known insecticidal compound from Piper species. The biologically active constituents of P. nigrum fruits were characterized as the isobutylamide alkaloids pellitorine, guineensine, pipercide, and retrofractamide A by spectroscopic analysis. Retrofractamide A was isolated from P. nigrum fruits as a new insecticidal principle. On the basis of 48-h LC(50) values, the compound most toxic to C. pipiens pallens larvae was pipercide (0.004 ppm) followed by retrofractamide A (0.028 ppm), guineensine (0.17 ppm), and pellitorine (0.86 ppm). Piperine (3.21 ppm) was least toxic. Against A. aegypti larvae, larvicidal activity was more pronounced in retrofractamide A (0.039 ppm) than in pipercide (0.1 ppm), guineensine (0.89 ppm), and pellitorine (0.92 ppm). Piperine (5.1 ppm) was relatively ineffective. Against A. togoi larvae, retrofractamide A (0.01 ppm) was much more effective, compared with pipercide (0.26 ppm), pellitorine (0.71 ppm), and guineensine (0.75 ppm). Again, very low activity was observed with piperine (4.6 ppm). Structure-activity relationships indicate that the N-isobutylamine moiety might play a crucial role in the larvicidal activity, but the methylenedioxyphenyl moiety does not appear essential for toxicity. Naturally occurring Piper fruit-derived compounds merit further study as potential mosquito larval control agents or as lead compounds.     

Detecting ingested plant DNA in soil-living insect larvae

Although a significant proportion of plant tissue is located in roots and other below-ground parts of plants, little is known on the dietary choices of root-feeding insects. This is caused by a lack of adequate methodology which would allow tracking below-ground trophic interactions between insects and plants. Here, we present a DNA-based approach to examine this relationship. Feeding experiments were established where either wheat (Triticum aestivum) or maize (Zea mays) was fed to Agriotes larvae (Coleoptera: Elateridae), allowing them to digest for up to 72 h. Due to the very small amount of plant tissue ingested (max = 6.76 mg), DNA extraction procedures and the sensitivity of polymerase chain reaction (PCR) had to be optimized. Whole-body DNA extracts of larvae were tested for the presence of both rbcL and trnL plastid DNA using universal primers. Moreover, based on cpDNA sequences encoding chloroplast tRNA for leucine (trnL), specific primers for maize and wheat were developed. With both, general and specific primers, plant DNA was detectable in the guts of Agriotes larvae for up to 72 h post-feeding, the maximum time of digestion in these experiments. No significant effect of time since feeding on plant DNA detection success was observed, except for the specific primers in maize-fed larvae. Here, plant DNA detection was negatively correlated with the duration of digestion. Both, meal size and initial mass of the individual larvae did not affect the rate of larvae testing positive for plant DNA. The outcomes of this study represent a first step towards a specific analysis of the dietary choices of soil-living herbivores to further increase our understanding of animal-plant feeding interactions in the soil.     

Citrus limonoids and their semisynthetic derivatives as antifeedant agents against Spodoptera frugiperda larvae. A structure-activity relationship study

The antifeedant activity of Citrus-derived limonoids limonin (1), nomilin (2), and obacunone (3) and their semisynthetic derivatives 4-26 was evaluated against a commercially important pest, Spodoptera frugiperda. Simple chemical conversions were carried out on the natural limonoids obtained from seeds of Citrus limon. These conversions focused on functional groups considered to be important for the biological activity, namely the C-7 carbonyl and the furan ring. In particular, reduction at C-7 afforded the related alcohols, and from these their acetates, oximes, and methoximes were prepared. Hydrogenation of the furan ring was also performed on limonin and obacunone. The known antifeedant properties of the Citrus limonoids are confirmed. Comparison with previously reported data shows that insect species vary in their behavioral responses to these structural modifications. Highly significant antifeedant activity (P < 0.01) for two natural (1 and 3) and three semisynthetic limonoids (4, 8, and 10) was observed against S. frugiperda.     

6beta-hydroxygedunin from Azadirachta indica. Its potentiation effects with some non-azadirachtin limonoids in neem against lepidopteran larvae

The biological activity of 6beta-hydroxygedunin isolated from Azadirachta indica A. Juss. was assessed using the gram pod borer, Helicoverpa armigera (Hubner), and Asian armyworm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), alone and in combination with other limonoids, gedunin, salannin, nimbinene, and azadirachtin. The compound exhibited growth inhibitory activity in artificial diet bioassays, with 24.2 and 21.5 ppm, respectively, inhibiting growth by 50%. This efficacy was higher in comparison to gedunin (EC(50) = 50.8 and 40.4 ppm), salannin (EC(50) = 74.5 and 72.0 ppm), and nimbinene (EC(50) = 391.4 and 404.5 ppm). Azadirachtin, however, remained the most active neem allelochemical against both insect species. Nutritional assays clearly demonstrated that, though relative consumption and growth rates of fourth instar larvae were reduced, gedunin-type compounds induced physiological toxicity, evident by reduced efficiency of conversion of ingested food (ECI) in feeding experiments. Salannin and nimbinene, on the contrary, induced concentration-dependent feeding deterrence only. In feeding experiments, combinations of the compounds revealed that when azadirachtin was present in a mixture, EC(50) values did not deviate from the individual efficacy of azadirachtin (0.26 and 0.21 ppm, respectively) against H. armigera and S. litura larvae. However, a combination without azadirachtin did show a potentiation effect with potent EC(50) values among structurally different molecules, i.e., when salannin or nimbinene was combined with 6beta-hydroxygedunin or gedunin rather than structurally similar salannin + nimbinene or 6beta-hydroxygedunin + gedunin. Obviously, azadirachtin being the most active compound in neem is not synergized or influenced by any other limonoid, but other non-azadirachtin limonoids were more potent in specific combinations vis-à-vis the structural chemistry of the compound. It is obvious from the present study that potentiation among non-azadirachtin limonoids having explicitly two different modes of action, such as feeding deterrence and physiological toxicity, may be playing a significant role in the potentiation effect.     

杀虫剂对草地贪夜蛾幼虫的室内防效测定

草地贪夜蛾已经对多种杀虫剂产生了严重抗性,为筛选应急防控特效药剂,采用浸叶法研究了国家农业农村部推荐用于草地贪食蛾应急防控药剂清单中的7种不同作用机理杀虫剂对草地贪夜蛾甘肃种群3龄幼虫的室内防效。结果表明,60 g/L乙基多杀菌素悬浮剂2 000倍液、5 000倍液和2%甲维盐乳剂2 000倍液、 4 000倍液处理对草地贪夜蛾3龄幼虫杀虫活性最好,药后24、48 h的校正防效均为100%。其次为0.5%苦参碱水剂300倍液、10%啶虫脒乳油1 000倍液和200 g/L氯虫苯甲酰胺悬浮剂2 000倍液处理,48 h的校正防效分别为82.86%、88.73%、88.57%。生物源农药8 000 IU/uL苏云金杆菌悬浮剂100倍液处理速效性稍差,72 h后校正防效仅为43.28%;4.5%高效氯氰菊酯乳油1 000倍液、1 500倍液处理48 h的校正防效均不足30%,表明草地贪夜蛾可能对该药产生严重的抗性。     

Synthesis and insect antifeedant activity of aurones against Spodoptera litura larvae

A series of aurones were prepared from various phenols via phenoxy acetic acids and coumaranones and evaluated for insect antifeedant activity against the common cutworm (Spodoptera litura). The naturally occurring aurone was most active at an ED50 of 0.12 micromol/cm2. The synthetic precursor, coumaranones, showed that the introduction of methoxyl and methyl groups to the benzene ring increased insect antifeedant activity. Similarly, the tested aurones showed that the introduction of methoxyl group to the A and/or B rings increased the insect antifeedant activity, but 4,5,6- and 3',4',5'-trisubstituted compounds did not show this activity in this test. The hydroxylation of aurones in the B ring should be disadvantageous for insect antifeedant activity against S. litura. Although the melting points did not correlate well with the insect antifeedant activity, compounds that were nearly inactive had high melting points. A significant correlation was noted between biological activity (pED50) and a hydrogen-bonding parameter calculated from the Rf value obtained from SiOH thin-layer chromatography and a lipophilicity parameter (log k) calculated from the retention time in ODS high-performance liquid chromatography. The respective correlation coefficients (r) were -0.83 and -0.70. The introduction of alkoxy and alkyl groups along with adequate hydrogen bonding seems to contribute to the antifeedant activity of the compounds tested.     

蜂王浆三针夹取式拣虫机的设计与试验

蜂王浆拣虫是挖浆前必须完成的工序。由于蜜蜂幼虫个体较小、数目庞大,因此人工拣虫过程劳动强度非常大;然而中国养蜂人员老龄化日益严重,且目前蜂王浆拣虫机械化尚未成熟。该文针对中国养蜂现状提出一种以三针夹取的方式将王台中蜜蜂幼虫夹出的方法。以三针夹取的拣虫方式构建蜂王浆拣虫机整机方案。三根针在王台孔内壁同时做向心运动或分离运动,将蜜蜂幼虫夹住或松开。对传动机构中球面槽轮和凸轮的参数进行计算。通过有限元分析得出动力输入端脚踏板受力情况。计算得出球面槽轮圆柱销弧长7.5π,槽深20.68 mm;得出凸轮的理论廓线;有限元分析结果得出动力输入方式可靠。该机器在保留蜂王浆幼虫完整的前提下,一次性将整条王台(64孔)中蜜蜂幼虫全部拣出,可实现连续作业,拣虫效率为10条/min时为人工的10倍,克服了蜂场手工作业时间长和劳动强度大问题。对扩大中国蜂业养蜂规模有着极大的促进作用。     

Growth stimulating effect on queen bee larvae of histone deacetylase inhibitors

Royal jelly (RJ) is a widely used natural food. It is also a major source of nutrition for queen bees and plays a key role in their development. RJ is secreted from the hypopharyngeal and mandibular glands of young adult worker bees. The regulation of gene expression in these two glands may influence the development of queen bees by affecting the content of RJ. This study investigated the epigenetic effects in these two glands in young adult worker bees treated with histone deacetylase inhibitors (HDACis), a U.S. Food and Drug Administration-approved drug, suberoylanilide hydroxamic acid (SAHA), and NBM-HD-1, a novel compound synthesized in this laboratory. Western blot analyses indicated that the levels of acetyl-histone 3 and p21 protein expression in MCF-7 cells increased markedly after treatment with NBM-HD-1. The data proved that NBM-HD-1 was a novel and potent HDACi. Furthermore, a method of affecting epigenetic regulation of the mrjp family gene in the hypopharyngeal and mandibular glands of young adult worker bees was developed by feeding young adult worker bees HDACi. Epigenetic regulation produced several important biological effects. A marked change in the protein composition of the RJ secreted from these treated bees was found. Only the ratio of specific major royal jelly protein 3 (MRJP3) was significantly altered in the treated bees versus the untreated controls. Other MRJP family proteins did not change. This alteration in the ratio of royal jelly proteins resulted in a significant increase in the body size of queen bee larvae. The data seem to suggest that HDACis may play an important role in the epigenetic regulation of the hypopharyngeal and mandibular glands of young adult worker bees. They appear to change mrjp3 gene expression and alter the ratio of MRJP3 protein in RJ. This study presents the first evidence that HDACis are capable of regulating the ratio of MRJP3 proteins in RJ, which has the potential to change the body size of queen bees during their development.     

Impact of root herbivory by insect larvae on soil microbial communities

Bentgrass (Agrostis capillaris) and clover (Trifolium repens) were grown as pure swards and mixtures in pots containing soil from the NERC Soil Biodiversity field site located in Scotland. Six weeks after plant establishment leatherjacket larvae (Tipula paludosa) were added at field density to half the pots and the impacts of their feeding on plant shoot and root biomass and soil microbial communities was determined after 10 days. Plate counts and community level physiological profiles (CLPP) were used to characterise the microbial communities. Larval herbivory had a significant negative effect on shoot growth of both grass and clover and root biomass of grass. In mixed swards, larvae preferentially fed on clover. Soil microbial community structure was altered in the presence of larvae with populations of pseudomonads being significantly increased. These community differences may be attributed to increased quantity and qualitative changes in carbon flux to the soil as a result of root herbivory, as indicated by differences in the CLPPs of microbial communities in the presence and absence of larvae. This was mainly due to increased utilisation of some sugars, carboxylic and amino acids in the presence of larvae.     

植物提取物对菜青虫的拒食活性研究

测定了广西30科74种植物提取物对菜青虫4龄幼虫的拒食活性。结果表明,在10 m g/mL浓度下,处理24 h,拒食率在90%以上的有鸦胆子(果实)、番荔枝、灵香草和木防已等4种植物提取物;拒食率在80%~90%的有楝科一种A(学名待定)、海木、木花生、鸦胆子(枝叶)和毛鸦胆子(果实)等5种植物提取物;拒食率在70%~80%的有米仔兰、海南木和鱼藤等3种植物提取物;处理48 h,鸦胆子(果实)、番荔枝、灵香草和木防已等4种植物提取物仍然维持高拒食活性,拒食率在9 0%以上;拒食率在80%~90%仅有海木1种植物提取物;拒食率在70%~80%的有米仔兰、楝科一种A(学名待定)、鸦胆子(枝叶)和毛鸦胆子(果实)等4种植物提取物;其余的供试植物提取物24 h和48 h的拒食率均在70%以下。     

Activity of carbohydrases in the gut of Bibionidae (Diptera) larvae

Dipteran larvae play an important role in the soil of some deciduous forests. They can consume a considerable part of the annual litter fall and produce a large amount of faecal pellets, which are forming an important part of the fermentation horizon of forest soils. We measured the pH changes and assayed the activities and pH optima of saccharolytic enzymes in the digestive tracts of the larvae of Bibio pomonae and Penthetria holosericea (Bibionidae). The pH of the litter offered as a food was about 5. The gut content became highly alkaline (pH about 10) in the anterior part of the midgut and the pH decreased posteriorly and in the hindgut. Excrements were neutral or had slightly alkaline pH (7.5–8.0) in both species. The alkaline pH optima of amylase (9.5–10.0) and maltase (8.0), trehalase and cellobiase (7.0) were the same in both species. Saccharolytic activity showed an optimum at pH 7 in B. pomonae and at pH 8 in P. holosericea. Though there are previously published reports of high assimilation efficiency of bibionid larvae fed in litter (46–76% in B. pomonae), activities of both exo and endocellulases were below the detection limit of saccharolytic and chromolytic assays along a wide pH range (5–10). Possible explanations are discussed.