Dipsikha Bora

Comparative mode of action of some terpene compounds against octopamine receptor and acetyl cholinesterase of mosquito and human system by the help of homology modeling and Docking studies

Article history: Received on: 04/01/2013 Revised on: 21/01/2013 Accepted on: 05/02/2013 Available online: 27/2/2013 Mosquitoes are vectors of many diseases like malaria, encephalitis, dengue, filaria, yellow fever etc. and thus possess severe threat to public health. Essential oils of some aromatic plants and many pure terpene compounds have been reported effective against different strains of mosquitoes by many authors. In the present investigation, five reported terpene compounds namely eugenol, geraniol, coumarin, eucalyptol and carvacrol were allowed to dock against octopamine receptor and acetyl cholinesterase protein models of Aedes aegypti and Homo sapiens to evaluate their comparative efficacy in terms of docking performance. All the compounds were found to dock with both the protein models of the two animal systems while some of them were found to better perform against the protein models of A.aegypti than the protein models of H.sapiens which can further be explored in mosquito control programme as a comparatively safe compound(s). The results are discussed on the basis of energy value. 3D structures of proteins were modeled using Modeller9v8. The structures assessment were established using the Procheck, WhatCheck and WhatIF server of Swiss Model Workspace. Ligands were prepared using the Commercial Software Exome Horizon.

Toxicity of essential oil compounds against Exorista sorbillans (Diptera: Tachinidae), a parasitoid of silkworm

Essential oils of Ageratum conyzoides and Ocimum species are potential candidates for management of Exorista sorbillans (Wiedemann) (Diptera: Culicidae), a serious pest of silkworm. Considering that the pure compounds in essential oil may exhibit efficacy against the parasitoid, contact and topical toxicity of 22 essential oil compounds found in plants like A. conyzoides , different chemotypes of Ocimum species, Cymbopogon citratus and Eucalyptus globulus were assessed against Exorista sorbillans . The compounds under study were terpenes and coumarin. Most of the compounds were toxic to E. sorbillans but their toxicity varied with the bioassay method. The LC 50 values of 11 compounds effective as contact fumigant, namely citral, geraniol, nerol, carvacrol, eugenol, isoeugenol, l-citronellol, carvone, coumarin, α-caryophyllene and terpinen-4-ol were 110.23, 124.11, 135.75, 194.53, 207.25, 266.40, 267.24, 299.23, 364.70, 533.02 and 1213.43 ppm, respectively. Topical application showed a different order of toxicity of the compounds. The compounds, α-pinene, 1,8-cineole, γ-terpinene, β-pinene, S-limonene and D-limonene which did not possess much efficacy as contact-fumigant were highly effective on topical application. We recommend the compounds found effective in this study for further studies to develop viable control agent against E. sorbillans , which is lacking at present. Key words : Essential oil, monoterpenes, coumarin, Exorista sorbillans, silkworm.

Plant Based Pesticides: Green Environment with Special Reference to Silk Worms

Pesticides once having entry to an environment either get into the complex web of life through food chain or different components of the environment through physical passages like drifting by air and aquatic runways. Such facts were meticulously described by Rachel Carson [1] in her book ‘Silent spring’ where she advocated for choosing either the chemical control or biological control to avoid creation of endless problems to mankind owing to pesticide use. Looking back at the history of tremendous potentiality of synthetic chemicals to manage insect pests followed by subsequent cases of failure of chemical control due to development of insect resistance and pest resurgence, here we intend to cite examples of selective toxicity of insecticides and reiterate its importance in management of insect pests. Pesticidal pollution is a global problem. Use of synthetic insecticides to control pest around the world has resulted in disturbances of the environment, secondary pest resurgence, pest resistance to pesticides, lethal effects to non-target organisms as well as direct toxicity to users. It has been reported that about 2.5 million tons of pesticides are used on crops each year and the worldwide damage caused by pesticides reaches

Host plant selection by larvae of the muga silk moth, Antheraea assamensis, and the role of the antenna and maxillary palp.

100 billion annually. The reason behind this amount of cost is the high toxicity and non biodegradable properties of pesticides and the residues in soil, water resources and crops that affect public health [2]. Hence search for the environment friendly, highly selective, newer biodegradable pesticides for pest management programme has been advocated to be essential for last several decades.

Growth inhibitory effect of phenolic extracts of Ziziphus jujuba Mill. in dengue vector Aedes aegypti (L) in parent and F1 generation

Abstract The importance of olfactory senses in food preference in fifth instar larvae of Antheraea assamensis Helfer (Lepidoptera: Saturniidae) was examined by subjecting larvae with only antennae or maxillary palpi after microsurgery to food and odor choice tests. Mean percent consumption, total consumption, and choice indices were used as parameters for drawing conclusions. The foods used were two hosts, two non-hosts, and a neutral medium (water). Both antennae and maxillary palpi were fully competent in preference for host plants, Persea bombycina Kostermans (Laurales: Lauraceae) and Litsea polyantha Juss, over the non-hosts, Litsea grandifolia Teschner and Ziziphus jujuba Miller (Rosales: Rhamnaceae). Both were competent in rejecting the non-hosts, L. grandifolia and Z. jujuba. The odor choice test was carried out using a Y-tube olfactometer and showed similar results to the ingestive tests. The results indicate the necessity of functional integration of a combination of olfactory and gustatory sensilla present in different peripheral organs in food acceptance by A. assamensis larvae.

Restricted diet breadth of the larvae of Antheraea assamensis and the role of the labrum‐epipharynx and galeal sensilla

OBJECTIVE To evaluate the lethal and emergence inhibitory effect of alkaloid, phenolic and terpenoid extracts of Ziziphus jujuba (Rhamnaceae) against Aedes aegypti (Diptera: Culicidae), and to explore the effect of the most effective fraction on developmental and biochemical parameters of the dengue vector. METHODS The fourth instar larvae of Ae. aegypti were exposed to alkaloid, phenolic and terpenoid extracts from Z. jujuba leaves to test their toxicity and emergence inhibitory effects. Phenolic extract, being the most effective was further tested against the mosquitoes for their growth inhibitory effect supported by biochemical changes in the parent and F1 generation. RESULTS While the different secondary metabolite fractions i.e., alkaloid, phenolics and terpenoid caused mortality at larval and pupal stages, the LC50 value was the lowest for phenolic fraction. Further study carried out with the phenolic fraction revealed that it affected growth by decreasing adult life span, fertility and fecundity of the mosquitoes. The reduction in growth was also accompanied by decrease in carbohydrate and lipid levels. CONCLUSIONS It is concluded that the phenolic extract of the leaves of Z. jujuba is a potential candidate for control of Aedes mosquitoes.

Role of Visual Cues in Host Searching Behaviour of Exorista sorbillans Widemann, a Parasitoid of Muga Silk Worm, Antheraea assama Westwood

The silkworm, Antheraea assamensis Helfer (Lepidoptera: Saturniidae), grows primarily on Persea bombycina and Litsea polyantha. To understand if the restricted diet breadth is due to the specific role of gustatory sensilla of the larvae of A. assamensis, the same fifth instar larvae retaining only labrum‐epipharynx or galeal sensilla were subjected to food choice tests. The foods used were leaves of two host‐plant and two non‐host‐plant species. Mean per cent consumption and per cent of choosing larvae were used as parameters for drawing conclusions. The finding indicated involvement of the labrum‐epipharynx for acceptance and galeal sensilla for rejection of a non‐host‐plant species. Scanning electron microscope studies revealed the presence of two sensilla on the galea, one lateral and one medial sensilla styloconicum and two gustatory sensilla in the epipharynx of A. assamensis. The study revealed the key role of galeal sensilla in the restrictive diet‐breadth of A. assamensis.