Anti-insect Activity Research Articles

Application of the Scorpion Neurotoxin AaIT against Insect Pests.

Androctonus australis Hector insect toxin (AaIT), an insect-selective toxin, was identified in the venom of the scorpion Androctonus australis. The exclusive and specific target of the toxin is the voltage-gated sodium channels of the insect, resulting in fast excitatory paralysis and even death. Because of its strict toxic selectivity and high bioactivity, AaIT has been widely used in experiments exploring pest bio-control. Recombinant expression of AaIT in a baculovirus or a fungus can increase their virulence to insect pests and diseases vectors. Likewise, transgenic plants expressing AaIT have notable anti-insect activity. AaIT is an efficient toxin and has great potential to be used in the development of commercial insecticides.

Pinene-rich essential oils from Haplophyllum dauricum (L.) G. Don display anti-insect activity on two stored-product insects

Continuous use of synthetic insecticides increases environmental contamination and resistance in many species. Botanical insecticides, such as essential oil, were considered to be suitable alternatives due to multiple modes of action and low mammalian toxicity. Haplophyllum dauricum is a overlooked plant for the control of stored-product insects. Five essential oils (EOs) from Haplophyllum dauricum collected in October and November, rich in pinene, were extracted and evaluated on anti-insect activity against two stored-product insects, Tribolium castaneum (Coleoptera: Tenebrionidae) and Lasioderma serricorne (Coleoptera: Anobiidae). The lethal doses (LD50 and LD90), lethal concentrations (LC50 and LC90) and percentage repellency (PR) were evaluated. The GC-MS analysis showed that pinene (α-pinene and β-pinene) were major constituent of the EOs (54.61% and 57.33% in fruits, 46.80% in stems + leaves, and 30.57% in leaves), followed by β-phellandrene (14.49% and 21.34% in fruits and leaves), 3-carene (26.84% in leaves) and limonene (15.77%, 11.09%, 12.40%, 7.59%, and 6.24% in five EOs, respectively). Five EOs and selected major compounds provided promising fumigant, contact and repellent activity against T. castaneum and L. serricorne. The EO of stems + leaves collected in October showed the strongest contact toxicity on T. castaneum (LD50 = 20.21μg/adult), as well as fumigant and contact toxicity on L. serricorne (LC50 = 17.17 mg/L air, LD50 = 25.46 μg/adult). All the five EOs exhibited effective repellent activity (PR>80%) against T. castaneum. The results highlight that the EOs from H. dauricum have a promising potential as eco-friendly botanical insecticides.

Research and Development of Proteins and Peptides with Therapeutic Potential from Yam Tubers.

We discuss the diverse biological activities, therapeutic potential, and clinical applications of peptides and proteins isolated from various yams species including Dioscorea opposita Thunb (Chinese yam), D alata, D japonica (Japanese yam), D pseudojaponica, D batatas (Korea yam), and D cayenensis. Yam peptides and proteins have many pharmacological activities including immunomodulatory, antioxidant, estrogen-stimulating, osteogenic, angiotensin I-converting enzyme inhibiting, carbonic anhydrase and trypsin inhibiting, chitinase, anti-insect, anti-dust mite, lectin, and anti-proliferative activities. Yam peptides and proteins have therapeutic potential for treating cardiovascular diseases, inflammatory diseases, cancers, aging disorders, menopause, and osteoporosis.

Identification and Structure Elucidation of Janthitrems A and D from Penicillium janthinellum and Determination of the Tremorgenic and Anti-Insect Activity of Janthitrems A and B.

New compounds, 11,12-epoxyjanthitrem B (1) and 11,12-epoxyjanthitrem C (4), were isolated from Penicillium janthinellum and given the trivial names janthitrem A and janthitrem D, respectively. The known compounds janthitrem B (2) and janthitrem C (3) were also isolated, and NMR assignments were made for all four compounds. This showed that the previously published NMR assignments for 3 needed considerable revision. 1 and 2 were used as model compounds for the more complex, and highly unstable, epoxyjanthitrems that have been isolated from perennial ryegrass infected with the AR37 endophyte and which contain an epoxide group analogous to that of 1. Both 1 and 2 induced tremors in mice and reduced weight gain and food consumption of porina ( Wiseana cervinata) larvae, although 1 showed greater potency. This shows the importance of the epoxy group and suggests that epoxyjanthitrems are likely to be involved in the observed effects of the AR37 endophyte on livestock and insects.

Rice Secondary Metabolites: Structures, Roles, Biosynthesis, and Metabolic Regulation.

Rice (Oryza sativa L.) is an important food crop providing energy and nutrients for more than half of the world population. It produces vast amounts of secondary metabolites. At least 276 secondary metabolites from rice have been identified in the past 50 years. They mainly include phenolic acids, flavonoids, terpenoids, steroids, alkaloids, and their derivatives. These metabolites exhibit many physiological functions, such as regulatory effects on rice growth and development, disease-resistance promotion, anti-insect activity, and allelopathic effects, as well as various kinds of biological activities such as antimicrobial, antioxidant, cytotoxic, and anti-inflammatory properties. This review focuses on our knowledge of the structures, biological functions and activities, biosynthesis, and metabolic regulation of rice secondary metabolites. Some considerations about cheminformatics, metabolomics, genetic transformation, production, and applications related to the secondary metabolites from rice are also discussed.

Toxicity of four Cuban botanical derivatives against two stored-products coleopteran pests: Poster

Plants are a source of substances for protection of stored products. The Cuban flora has not yet been fully studied as a source of pesticides for postharvest protection, partly due to its great diversity. The toxicity of four Cuban plant derivatives against Lasioderma serricorne (F.) and Sitophilus zeamais Motschulsky was investigated. The anti-insect activity of the powders and the essential oil from plants belonging to Asteraceae, Fabaceae and Piperaceae was tested. Mortality and emergence of adult insects and the repellent effect of products were evaluated. Two products derived from Piper aduncum subsp. ossanum, caused high mortality (81,6 and 100%), reduced emergence (27,9 and 0,4%) and exhibited strong repellent activity on L. serricorne. Against S. zeamais, treatments with the highest mortality values were stems of Lonchocarpus punctatus (72,4%), seeds and stems of Canavalia ensiformis (64,9 and 69,9%), and leaves of Tithonia diversifolia (67,2%). The progeny production of S. zeamais was inhibited by powders of L. punctatus stems (31,8%), C. ensiformis seeds (40,5%), leaves (43,7%) and stems (30,6%), and T. diversifolia leaves (38,7%). The stems of C. ensiformis, leaves of T. diversifolia and L. punctatus had the highest repellent effect. These products have potential for small-scale treatments of grains for protection against both insects, and P. aduncum subsp. ossanum-based products to control L. serricorne infestation in tobacco. Identification of local candidates to develop effective and safe pesticides offers new alternatives to the Cuban agriculture in the control of storage pests.

Daphnauranins A and B, two new antifeedants Isolated from Daphne aurantiaca roots

Daphnauranins A (1) and B (2), two sesquiterpenoids were isolated from the roots of Daphne aurantiaca Diels. One is an unprecedented 5/7 oxacycloheptane ring system, the other is a sesquiterpene-lignan complex. Their structures were elucidated by comprehensive spectroscopic methods including MS and NMR. Their absolute configurations were further confirmed by the quantum ECD calculations. Daphnauranins A and B showed anti-insect activities against male fruit fly with anti-feeding rate up to 46.2±7.1 and 44.7±5.4% at 1mM, respectively.

Sauromatum guttatum lectin: Spectral studies, lectin-carbohydrate interaction, molecular cloning and in silico analysis

Non-immune carbohydrate binding proteins are broadly defined as lectins. Having been reported from all kingdoms of life, phytolectins are the most widely studied group of lectins. Sauromatum guttatum agglutinin (SGA) was isolated from the plant tubers and characterized for structural variations due to solvent perturbation using polarimetry, fluorescence and light scattering. For the β-sheet rich SGA, a pH and temperature induced molten globule like intermediate was identified. In isothermal titration microcalorimetry, SGA demonstrated cooperative binding to a complex glycoprotein in enthalpically driven mechanism. Fine sugar specificity exploration identified core pentasaccharide as the most common and highest binding motif with complex N-glycans and fucosylated core N-glycans as additional motifs. Molecular cloning of SGA which has previously been demonstrated to have anti-cancer and anti-insect activities is being reported for the first time. Full length cDNA sequence was obtained with RACE-PCR based upon the conserved carbohydrate recognition site [QXDXNXVXY] present in all GNA-related lectins. Quaternary structure was proposed by homology modeling and an attempt was made to explain the structure-function relationship by in silico analysis.

Development of anti-insect multilayered films for brown rice packaging that prevent Plodia interpunctella infestation

The aim of this study was to develop a multilayered insect-proof film that prevents contamination with Plodia interpunctella (Hübner; Lepidoptera: Pyralidae) insect larvae. The anti-insect activities of five essential oils (EOs), allyl disulfide (AD), and allyl mercaptan isolated from garlic and onion, respectively, were evaluated. Subsequently, fumigation insecticidal assays were performed to identify the anti-insect agents, their optimal concentrations. Garlic, onion EOs and their compounds were chosen as efficient anti-insect agents for application to rice flour-based multilayered plastic films. Penetration tests were then used to evaluate the ability of multilayered films to resist invasion by P. interpunctella larvae. Films containing 5% AD (AD-5) had the strongest resistance to penetration by insects. Thus, AD-5 was applied to brown rice packaging to measure protection from insects and to assess sensory properties. In these analyses, AD-5 showed insect-proofing effects and no undesirable changes to the sensory properties of the rice after cooking. Hence, this novel multilayer film could be used as an active packaging material with effective anti-insect activities and desirable physical properties.

Antifungal plant defensins: increased insight in their mode of action as a basis for their use to combat fungal infections.

Plant defensins are small, cationic peptides with a highly conserved 3D structure. They have been studied extensively in the past decades. Various biological activities have been attributed to plant defensins, such as anti-insect and antimicrobial activities, but they are also known to affect ion channels and display antitumor activity. This review focuses on the structure, biological activity and antifungal mode of action of some well-characterized plant defensins, with particular attention to their fungal membrane target(s), their induced cell death mechanisms as well as their antibiofilm activity. As plant defensins are, in general, not toxic to human cells, show in vivo efficacy and have low frequencies of resistance occurrence, they are of particular interest in the fight against fungal infections.

Insecticidal Properties of a Highly Potent Wax Isolated from Dolichandra cynanchoides Cham.

Bioassay-guided fractionation of an ethanolic extract of the aerial parts of Dolichandra cynanchoides Cham. (Bignoniaceae) led to the isolation of a natural wax with anti-insect activity against Spodoptera frugiperda (Noctuidae) and Epilachna paenulata (Coleptera). The compound was identified spectroscopically as an ester of a C27 fatty acid and a C25 alcohol, pentacosyl heptacosanoate (1). The effective doses of 1 for 50% feeding inhibition (ED50) of S. frugiperda and E. paenulata were 0.82 and 8.53 µg/cm2, respectively, in a choice test, while azadirachtin showed ED50 of 0.10 and 0.59 µg/cm2, respectively. In a no-choice test, both insects refused to feed on leaves treated with 1 at doses of 0.1 µg/cm2 or greater inhibiting larval growth and dramatically reducing survival. The lethal doses 50 (LD50) of 1 were 0.39 and 0.68 µg/cm2 for S. frugiperda and E. paenulata, respectively. These results indicate that 1 has potential for development as botanical insecticides. Similar esters might be obtainable in large quantities as many edible crops produce wax esters that are discarded during food processing. Research on these materials could lead to the detection of similar waxes with insecticidal activity.

Hyptis suaveolens seed powder as a repellent against Callosobruchus maculatus (Coleoptera: Bruchidae) on cowpea

Hyptis suaveolens is a common weed that can be found growing on wasteland in The Gambia. It is traditionally used as a mosquito repellent in many homes in the rural areas and belongs to the Labiatae family, a rich source of compounds with anti-insect activity. In this study, the anti-insect activity of ground H. suaveolens seeds on the cowpea seed weevil Callosobruchus maculatus was investigated using a two choice ‘Y’ olfactometer. Six concentrations of 1, 2, 4, 6, 8, and 10% w/w were prepared. Ten adult insects of mixed sexes were released into the response chamber and each test was replicated eight times. A high repellency action of up to 80% was recorded on the highest concentration of 10% w/w when the weevils were allowed to choose between cowpea seeds treated with ground H. suaveolens seed powder and the untreated seeds which served as control. Results from this research strongly suggest that H. suaveolens seed powder can be used as a botanical pesticide to reduce C. maculatus infestation in storage. Since, it is easily available, farmers can make their own formulation at little or no cost.

The effects of transgenic Cry1Ac+Cry2Ab cotton on cotton bollworm control and functional response of predators on whitefly

In this study, we detected and clarified the roles of transgenic Cry1Ac+Cry2Ab cotton "639020" in controlling cotton bollworm (Helicoverpa armigera) during critical periods of bud stage (second generation of bollworm), flowering stage (third generation of bollworm) and bolling stage (fourth generation of bollworm) as well as the influences of 639020 cotton on functional response of the main predators (Chrysopa sinica larvae, Propylaea japonica, Orius and Erigonidium graminicola ) on whitefly using transgenic Cry1Ac cotton "CCRI41" and conventional cotton "CCRI49" as the control. Our results showed that the 639020 cotton well controlled the second and third generation of bollworm, and the level of insect resistance increased by 52.85% and 16.22% separately compared with that of CCRI41, with a significant effect on the second generation of bollworm. Moreover, the number of bollworm eggs in 639020 cotton field was lower than that in CCRI41 and CCRI49 cotton fields (except the second generation of bollworm) during the cotton bud, flowering and bolling stages. Although the number of bollworm larvae in 639020 cotton field was significantly lower than that in CCRI49 field, and both under the controlling index, it has no significant difference compared with that in CCRI41 cotton field. There were also no obvious changes in predator functions of Chrysopa sinica, Propylaea japonica, Orius and Erigonidium graminicola on bemisia tabaci between 639020, CCRI41 and CCRI49 cotton filed. This study evaluated the safety of new transgenic cotton on environment, anti-insect activity of exogenous gene and the safety of production and application prospect.

Differential anti-insect activity of natural products isolated from Dodonaea viscosa Jacq. (Sapindaceae)

Abstract Botanical biopesticides constitute an important tool for Integrated Pest Management practices. Uruguay has a great potential for developing botanical biopesticides from its abundant native flora. Dodonaea viscosa Jacq. is a native Sapindaceae that in preliminary studies was shown to possess a potential deterrent activity against insect models. In this work, ethanolic extracts of the leaves of this species were studied. Bioguided fractionation and supercritical fluid extraction led to the isolation of active compounds. For that purpose four insect models were used: Epilachna paenulata, Spodoptera littoralis, Myzus persicae, and Rhopalosiphum padi, which are pests of crops of economic importance. Lupeol, stigmasterol, stigmast-7-en-3-ol, and a labdane diterpene were isolated and showed differential activity against the models.

Uncovering the defence responses of Eucalyptus to pests and pathogens in the genomics age.

Long-lived tree species are subject to attack by various pests and pathogens during their lifetime. This problem is exacerbated by climate change, which may increase the host range for pathogens and extend the period of infestation by pests. Plant defences may involve preformed barriers or induced resistance mechanisms based on recognition of the invader, complex signalling cascades, hormone signalling, activation of transcription factors and production of pathogenesis-related (PR) proteins with direct antimicrobial or anti-insect activity. Trees have evolved some unique defence mechanisms compared with well-studied model plants, which are mostly herbaceous annuals. The genome sequence of Eucalyptus grandis W. Hill ex Maiden has recently become available and provides a resource to extend our understanding of defence in large woody perennials. This review synthesizes existing knowledge of defence mechanisms in model plants and tree species and features mechanisms that may be important for defence in Eucalyptus, such as anatomical variants and the role of chemicals and proteins. Based on the E. grandis genome sequence, we have identified putative PR proteins based on sequence identity to the previously described plant PR proteins. Putative orthologues for PR-1, PR-2, PR-4, PR-5, PR-6, PR-7, PR-8, PR-9, PR-10, PR-12, PR-14, PR-15 and PR-17 have been identified and compared with their orthologues in Populus trichocarpa Torr. & A. Gray ex Hook and Arabidopsis thaliana (L.) Heynh. The survey of PR genes in Eucalyptus provides a first step in identifying defence gene targets that may be employed for protection of the species in future. Genomic resources available for Eucalyptus are discussed and approaches for improving resistance in these hardwood trees, earmarked as a bioenergy source in future, are considered.

Expression of a wolf spider toxin in tobacco inhibits the growth of microbes and insects

Lycotoxin I, from the wolf spider (Lycosa carolinensis), is an amphipathic pore-forming peptide that has antimicrobial and anti-insect activity. Constitutive expression of a lycotoxin I modified for oral toxicity to insects in tobacco (Nicotiana tabacum) conferred significantly enhanced resistance to larvae of the corn earworm (Helicoverpa zea) and cigarette beetle (Lasioderma serricorne). Gene expression levels of modified lycotoxin I were negatively correlated to the survival of corn earworm larvae. In addition, pathogenic symptoms caused by Pseudomonas syringae pathovar tabaci and Alternaria alternata on the modified lycotoxin I-expressing leaves were significantly less severe than on wild type leaves. These results indicate that modified lycotoxin I expression in tobacco can potentially protect leaf tissue from a broad spectrum of pests and pathogens.

Transcriptomic response of cowpea bruchids toN-acetylglucosamine-specific lectins

Griffonia simplicifolia lectin II (GSII) and wheat germ agglutinin (WGA) are N-acetylglucosamine-binding lectins. Previous studies demonstrated that they have anti-insect activity, a property potentially useful in pest control. To gain some insight into the insect response to dietary lectins, we performed transcriptomic analysis using the cowpea bruchid (Callosobruchus maculatus) midgut microarray platform we built. Compared to the nonnutritional cellulose treatment, dietary lectins induced more profound changes in gene expression. Ingestion of relatively high doses of lectins for 24 h resulted in alteration of gene expression involved in sugar and lipid metabolism, transport, development, defense, and stress tolerance. Metabolic genes were largely downregulated. Moreover, we observed disorganized microvilli resulting from ingestion of WGA. This morphological change is consistent with the lectin-induced changes in genes related to midgut epithelial cell repair. In addition, suboptimal nutrient conditions may serve as a stress signal to trigger senescence processes, leading to growth arrest and developmental delay.

Bio-Assay Guided Fractionation of Anti-Mosquito Limonoids from Turraea abyssinica and Turraea cornucopia

Malaria, transmitted by mosquitoes of the genus Anopheles, is the most important parasitic disease worldwide. It affects 40% of the global population mostly within the tropical world. Yearly, over one million children under the age of five die in Africa as a result of malaria. The genus Turraea belongs to the family Meliaceae. Meliaceae is characterized by the presence of tetranortriterpenoids (limonoids), a group of compounds that exhibit a wide variety of biological properties including anti-insect, anti-protozoa, anti-bacterial and anti-fungal activities. In the present study, the root bark of T. abyssinica and T. cornucopia were extracted with methanol and partitioned between water and chloroform. The activity of crude methanol and chloroform extracts was tested against larvae and adults of Anopheles gambiae sensu stricto (Diptera: Culicidae). As larvicides, the methanol extract of T. cornucopia was the most active (LD50 202 ppm). The chloroform extract of T. cornucopia was the most active as an adulticide (LD50 302.1 ppm). Partitioning of the methanolic extracts between chloroform and water, followed by silica gel chromatography of the organic extract gave limonoids-rich fractions that had larvicidal activity higher than those of the corresponding crude extracts. Column chromatography of the chloroform fraction followed by semi-preparative HPLC yielded 1α-12α-diacetoxy-1,2-dihydro-7-deacetyl-3β-7α-dihydroxyazadiron,12α-acetoxy-7-deacetylazadiron and mzikonone. The structures of these compounds were elucidated using spectroscopic methods (IR UV, MS, 1H-, 13C- NMR, gradient COSY, and gradient HMBC experiments). Stereo chemical assignments were made by gradient NOE spectroscopy. These plants offer a significant potential for mosquito control as larvicides and adulticides.

Short and long-term antinutritional effect of the trypsin inhibitor ApTI for biological control of sugarcane borer

Plant-derived trypsin inhibitors have been shown to have potent anti-insect effects and are a promising alternative for the biological control of pests. In this work, we tested the anti-insect activity of Adenanthera pavonina trypsin inhibitor (ApTI) against Diatraea saccharalis larvae, a major insect pest in sugarcane. The addition of 0.1% ApTI in short-term assays resulted in 87% and 63% decreased trypsin and chymotrypsin activities respectively. ApTI was not digested after 60h incubation with D. saccharalis midgut proteases. The chronic effects of ApTI on F0 and F1 generations of D. saccharalis were also analyzed. The larvae from the F0 generation showed 55% and 21% decreased larval and pupal viability, respectively. ApTI-fed larvae from the F1 generation showed a decrease of 33% in survival rate and 23% in the average larval weight. Moreover, ApTI treatment reduced trypsin and chymotrypsin activities in F1 larvae. Thus, the anti-insect effects of ApTI on consecutive generations (F0 and F1) of D. saccharalis larvae demonstrate its potential for long-term control of this pest.

Activities of Apiaceae Essential Oils against Armyworm, Pseudaletia unipuncta (Lepidoptera: Noctuidae)

Essential oils (EOs) from four Apiaceae species and 11 pure compounds were evaluated for their antifeedant, growth inhibitory, and insecticidal activities against Pseudaletia unipuncta (Lepidoptera: Noctuidae) fourth-instar larvae. EOs from Foeniculum vulgare subsp. vulgare var. vulgare, Anethum graveolens , Petroselinum crispum , and Cuminum cyminum were characterized by gas-chromatography (GC) and mass spectrometry. Anti-insect activity varied according to plant specie/composition, type, and exposure period. EOs from P. crispum and A. graveolens fruits, trans-anethole and cuminaldehyde, exerted acute effects on larvae feeding and growth (FDI and GI > 70%). A. graveolens , C. cyminum , and F. vulgare EOs and some of their constituents were effective by fumigation (≥ 80%). Satisfactory contact toxicities (>70%) were observed for five compounds and all EOs, except F. vulgare EOs, when tested by the filter paper impregnation method. For the most active EOs/compounds, dose-dependent toxicity was determined and inverse relationships of LC50 with time were established.