The cytotoxic norditerpene dilactones of Podocarpus milanjianus and Podocarpus sellowii

The cytotoxic norditerpene dilactones nagilactone F and its new congener nagilactone G have been isolated from the bark constituents of Podocarpus milanjianus and Podocarpus sellowii. The diterpenes totarol, 19-oxototarol and macrophyllic acid were also isolated.     

Isolation and identification of two new biologically active norditerpene dilactones from Aspergillus wentii

Two new biologically-active norditerpenoid dilactones were purified from culture extracts of Aspergillus wentii and assigned the trivial names wentilactone A and wentilactone B. The absolute chemical structure of wentilactone A was determined by single crystal X-ray diffraction and circular dichroism. The structure of wentilactone B was determined by ¹H and ¹³C NMR analyses. Wentilactone A had an ld₅₀ of 7.0 mg/kg when administered orally to 1-day-old chickens. Both metabolites inhibited growth in wheat coleoptile bioassays.     

The biology of insecticidal activity and resistance

Identifying insecticide resistance mechanisms is paramount for pest insect control, as the understandings that underpin insect control strategies must provide ways of detecting and managing resistance. Insecticide resistance studies rely heavily on detailed biochemical and genetic analyses. Although there have been many successes, there are also many examples of resistance that still challenge us. As a precursor to rational pest insect control, the biology of the insect, within the contexts of insecticide modes of action and insecticide metabolism, must be well understood. It makes sense to initiate this research in the best model insect system, Drosophila melanogaster, and translate these findings and methodologies to other insects. Here we explore the usefulness of the D. melanogaster model in studying metabolic-based insecticide resistances, target-site mediated resistances and identifying novel insecticide targets, whilst highlighting the importance of having a more complete understanding of insect biology for insecticide studies.     

The insecticidal activity of recombinant garlic lectins towards aphids

The heterodimeric and homodimeric garlic lectins ASAI and ASAII were produced as recombinant proteins in the yeast Pichia pastoris. The proteins were purified as functional dimeric lectins, but underwent post-translational proteolysis. Recombinant ASAII was a single homogenous polypeptide which had undergone C-terminal processing similar to that occurring in planta. The recombinant ASAI was glycosylated and subject to variable and heterogenous proteolysis. Both lectins showed insecticidal effects when fed to pea aphids (Acyrthosiphon pisum) in artificial diet, ASAII being more toxic than ASAI at the same concentration. Acute toxicity (mortality at 3d exposure) was observed over the concentration range 0.125-2.0mgml(-1). The recombinant lectins caused mortality in both symbiotic and antibiotic-treated aphids, showing that toxicity is not dependent on the presence of the bacterial symbiont (Buchnera aphidicola), or on interaction with symbiont proteins, such as the previously identified lectin "receptor" symbionin. A pull-down assay coupled with peptide mass fingerprinting identified two abundant membrane-associated aphid gut proteins, alanyl aminopeptidase N and sucrase, as "receptors" for lectin binding.     

The insecticidal activity of beauvericin and the enniatin complex

The insecticidal activity of a complex mixture of enniatins, cyclohexadepsipeptides produced by Fusarium lateritium, a pathogen of the scale insect Hemiberlesia rapax, is compared with that of enniatin A and beauvericin in two bioassays against Calliphora erythrocephala and Aedes aegypti.     

The insecticidal activity of foliage from New Zealand conifers

When incorporated into artificial diets, the milled foliages of many New Zealand conifers are toxic to larvae of housefly (Musca domestica), codling moth (Laspeyresia pomonella) and light-brown apple moth (Epiphyas postvittana). The most toxic foliages are those of Podocarpus nivalis which contains diterpene lactones, and Dacrydium laxifolium, which has a high concentration (1%) of phytoecdysones. The insecticidal activities of the plants are discussed in relation to their insect associations, chemistry and taxonomy.     

Modulation of a lectin insecticidal activity by carbohydrates

Lectins from plants present an insecticidal activity most probably through their carbohydrate binding properties; as a consequence, their toxicity should vary with the presence of a competitive sugar in the ingested food. In order to test this hypothesis, we performed competition experiments between insecticidal activity and carbohydrate binding. For this purpose, we used a lectin from Lathyrus ochrus and the specific carbohydrate for this protein, glucose. In toxicological tests with Drosophila melanogaster, we observed a decrease of lectin toxicity when glucose was added to the larva-rearing medium. This result suggests that the toxicity of the lectin is correlated to its ability to bind sugar in the insect digestive tract and stresses the importance of sugar composition of the nutriment used for toxicological testing of lectins or in genetically modified plants.     

Secondary metabolites and insecticidal activity of Anemone pavonina

The insecticidal properties of the crude extracts of the leaves and flowers of Anemone pavonina were evaluated on Pheidole pallidula ants and showed significant levels of activity. Bioassay-guided fractionations led to the isolation of the butenolide ranunculin (1) as the active principle. Chemical investigations of the extracts showed them to contain as major components the sitosterol glycopyranoside lipids 2-5 and the glycerides 6-8. The structures of the metabolites were elucidated, following acetylation and hydrolysis of the natural products, by interpretation of their NMR and mass spectral data. The uncommon lipid metabolites 2-8 were isolated for the first time from the genus Anemone and this is the first report of insecticidal activity of the Anemone metabolite ranunculin against ants.     

Evolution of Bacillus thuringiensis Cry toxins insecticidal activity

Insecticidal Cry proteins produced by Bacillus thuringiensis are use worldwide in transgenic crops for efficient pest control. Among the family of Cry toxins, the three domain Cry family is the better characterized regarding their natural evolution leading to a large number of Cry proteins with similar structure, mode of action but different insect specificity. Also, this group is the better characterized regarding the study of their mode of action and the molecular basis of insect specificity. In this review we discuss how Cry toxins have evolved insect specificity in nature and analyse several cases of improvement of Cry toxin action by genetic engineering, some of these examples are currently used in transgenic crops. We believe that the success in the improvement of insecticidal activity by genetic evolution of Cry toxins will depend on the knowledge of the rate‐limiting steps of Cry toxicity in different insect pests, the mapping of the specificity binding regions in the Cry toxins, as well as the improvement of mutagenesis strategies and selection procedures.     

The parameters of comparative evaluation of insecticidal activity of preparations in aerosol containers

On the basis of experimental data, the authors present a group of parameters for the purpose of unification of comparative evaluation of the insecticidal effect of preparations in aerosol containers designed for combatting flying and non-flying domestic insects. The advisability of evaluation of the effect of the preparations for combatting flying insects according to the concentration of insecticides ensuring death of flies in the course of 15 min and the corresponding expenditure of the mixture has been substantiated. Preparations designed for combatting non-flying insects should be evaluated according to the coefficients of acute action, ovicidal and residual effects. To facilitate analysis and evaluation of the preparations in aerosol containers, the authors propose their classification according to the parameters of the insecticidal effect. Classification of the preparations under study according to their parameters is presented. It has been demonstrated that compositions containing pyrethroids and their mixtures with DDVP--Neofos, Neofos-2 and Pif-Paf are the most efficient.     

不同培养条件下红树林真菌1893菌株代谢产物的杀虫活性

本文以白纹伊蚊Aedes albopictus幼虫为试虫,以校正死亡率为指标,采用单因素法和正交设计法,对红树林真菌1893的营养条件进行了筛选,以期获得高活性的代谢产物.结果表明:以蔗糖10 g、酵母膏4 g、粗海盐6 g、MgSO4.7H2O 1 g、蒸馏水1000 mL,pH 6.5为培养条件时,代谢产物的相对效价最高,浓度为15mg/mL的代谢产物对3龄白纹伊蚊幼虫的毒杀死亡率达到了90.25%.     

Iridoid glucosides with insecticidal activity from Galium melanantherum

The insecticidal activity of the endemic species Galium melanantherum was evaluated against Crematogaster scutellaris ants and Kalotermes flavicollis termites. Iridoid glucosides 1-7 were isolated for the first time as metabolites of the investigated plant, along with the coumarin scopolin. The main components of the extract were found to be the non-acetylated iridoids: geniposidic acid (1), 10-hydroxyloganin (2), deacetyldaphylloside (3), monotropein (4), deacetylasperulosidic acid (5) and scandoside (6), while asperulosidic acid (7) was present only in minute quantities. All isolated metabolites were identified on the basis of their spectral data. Laboratory bioassays revealed significant levels of toxicity for 1-4 against Kalotermes flavicollis termites and Crematogaster scutellaris ants.     

Synthesis of some monosaccharide-related ester derivatives as insecticidal and acaricidal agents

To develop natural-product-based pesticidal agents, a series of monosaccharide-related ester derivatives (17a–q and 18a–f), glucose (xylose)-piperic acid/piperic acid-like conjugates, were synthesized. Three-dimensional structures of compounds 17b, 17g, 17h, and 17n were unambiguously determined by single-crystal X-ray diffraction. Especially compounds 18e and 18f exhibited the most potent insecticidal and acaricidal activities against Mythimna separata and Tetranychus cinnabarinus. Their structure-activity relationships were also discussed.     

Chemical intra-Mediterranean variation and insecticidal activity of Crithmum maritimum

The chemical composition of the volatile metabolites of Crithmum maritimum harvested from several geographic localities along the Mediterranean coasts was studied by GC and GC-MSD. The major oil constituents were found to be dillapiole, gamma-terpinene, sabinene, limonene and beta-phellandrene. The Western populations were richer in dillapiole, whereas the Southern collections were characterized by increased amounts of thymol methyl ether and gamma-terpinene. The Italian chemical profiles differentiated by the significant contributions of carvacrol methyl ether and isoterpinolene. The essential oils were also investigated for their insecticidal activity and their repellency against Pheidole pallidula (Nylander) ants and found to possess significant activity.     

九牛造杀虫活性成分研究

无公害农药具有杀虫活性高、无污染、与环境相容性好等特点,开发此类农药具有重要意义[1,2].     

Crown-capped imidacloprid: A novel design and insecticidal activity

Imidacloprid (IMI) derivatives conjugated with benzo-15-crown-5 and benzo-18-crown-6 structures, applied for the first time to explore novel insecticidal molecule, elicited strong excitatory toxic signs to the house flies and stunningly exhibited three to five times higher insecticidal activity than that of the parent IMI, yet the two benzo-crown structures themselves had no effect.