Evaluation of indigenous plants' extracts for mosquitocidal activity against different stages of Culex quinquefasciatus say (Diptera: Culicidae) / Avaliação de extratos de plantas indígenas quanto à atividade mosquitocida contra diferentes estágios de culex quinquefasciatus say (Diptera: Culicidae)

Abstract Being vector of West Nile Virus and falariasis the control of Culex quinquefasciatus is likely to be essential. Synthetic insecticide treatment is looking most effective for vectors mosquito control. However, these products are toxic to the environment and non-target organisms. Consequently, ecofriendly control of vectors mosquito is needed. In this regard botanical insecticide is looking more fruitful. Therefore, the present research aimed to investigate the effectiveness of methanolic extract and various fractions, including, n-hexane, ethyl-acetate, chloroform, and aqueous fraction, obtained from methanolic extract of Ailanthus altissima, Artemisia scoparia, and Justicia adhatoda using separating funnel against larval, pupal, and adult stages of Culex quinquefasciatus. The larvae and pupae of Culex quinquefasciatus were exposed to various concentrations (31.25-1000 ppm) of methanolic extract and its fractions for 24 hours of exposure period. For knock-down bioassay (filter paper impregnation bioassay) different concentration of the methanolic extract and its various fractions (i.e. 0.0625, 0.125, 0.25, 0.5 and 1mg/mL) were applied for 1 hour exposure period. The results were statistically analysed using standard deviation, probit analysis, and linear regression. The R2 values of larvae, pupae, and adult range from 0.4 to 0.99. The values of LC50 (concentration causing 50% mortality) for late 3rd instar larvae after 24 hours exposure period range from 93-1856.7 ppm, while LC90 values range from 424 -7635.5ppm. The values of LC50for pupae range form 1326.7-6818.4ppm and and values of LC90 range from 3667.3-17427.9ppm, respectively. The KDT50 range from 0.30 to 2.8% and KDT90 values range from1.2 to 110.8%, respectively. In conclusion, Justicia adhatoda may be effective for controlling populations of vector mosquito.

Resumo Por ser o vetor do vírus do Nilo Ocidental e da falaríase, o controle de Culex quinquefasciatus Say é provavelmente essencial. O tratamento com inseticida sintético parece ser mais eficaz para o controle dos mosquitos vetores. No entanto, esses produtos são tóxicos para o meio ambiente e organismos não visados. Consequentemente, o controle ecológico dos mosquitos vetores é necessário. Nesse sentido, o inseticida botânico parece mais produtivo. Portanto, a presente pesquisa teve como objetivo investigar a eficácia do extrato metanólico e de várias frações, incluindo n-hexano, acetato de etila, clorofórmio e fração aquosa, obtidos do extrato metanólico de Ailanthus altissima (Mill.) Swingle, Artemisia scoparia Waldst. & Kit. e Justicia adhatoda L. usando funil de separação contra os estágios larval, pupal e adulto de C. quinquefasciatus. As larvas e pupas de C. quinquefasciatus foram expostas a várias concentrações (31,25-1000 ppm) de extrato metanólico, e suas frações por 24 horas de período de exposição. Para o bioensaio knock-down (bioensaio de impregnação de papel de filtro), diferentes concentrações do extrato metanólico e suas várias frações (ou seja, 0,0625, 0,125, 0,25, 0,5 e 1 mg / mL) foram aplicadas por um período de exposição de 1 hora. Os resultados foram analisados ​​estatisticamente usando desvio padrão, análise Probit e regressão linear. Os valores de R2 de larvas, pupas e adultos variaram de 0,4 a 0,99. Os valores de LC50 (concentração que causa 50% de mortalidade) para larvas de terceiro estádio tardio após 24 horas de período de exposição variaram de 93-1856,7 ppm, enquanto os valores de LC90 variaram de 424-7635,5ppm. Os valores de LC50 para pupas variaram de 1326,7-6818,4 ppm e os valores de LC90 variaram de 3667,3-17427,9 ppm, respectivamente. O KDT50 variou de 0,30 a 2,8% e os valores de KDT90 variaram de 1,2 a 110,8%, respectivamente. Por fim, a espécie J. adhatoda pôde ser eficaz para controlar populações de mosquitos vetores.

Evaluation of indigenous plants' extracts for mosquitocidal activity against different stages of Culex quinquefasciatus say (Diptera: Culicidae) / Avaliação de extratos de plantas indígenas quanto à atividade mosquitocida contra diferentes estágios de culex quinquefasciatus say (Diptera: Culicidae)

Being vector of West Nile Virus and falariasis the control of Culex quinquefasciatus is likely to be essential. Synthetic insecticide treatment is looking most effective for vectors mosquito control. However, these products are toxic to the environment and non-target organisms. Consequently, ecofriendly control of vectors mosquito is needed. In this regard botanical insecticide is looking more fruitful. Therefore, the present research aimed to investigate the effectiveness of methanolic extract and various fractions, including, n-hexane, ethyl-acetate, chloroform, and aqueous fraction, obtained from methanolic extract of Ailanthus altissima, Artemisia scoparia, and Justicia adhatoda using separating funnel against larval, pupal, and adult stages of Culex quinquefasciatus. The larvae and pupae of Culex quinquefasciatus were exposed to various concentrations (31.25-1000 ppm) of methanolic extract and its fractions for 24 hours of exposure period. For knock-down bioassay (filter paper impregnation bioassay) different concentration of the methanolic extract and its various fractions (i.e. 0.0625, 0.125, 0.25, 0.5 and 1mg/mL) were applied for 1 hour exposure period. The results were statistically analysed using standard deviation, probit analysis, and linear regression. The R2 values of larvae, pupae, and adult range from 0.4 to 0.99. The values of LC50 (concentration causing 50% mortality) for late 3rd instar larvae after 24 hours exposure period range from 93-1856.7 ppm, while LC90 values range from 424 -7635.5ppm. The values of LC50for pupae range form 1326.7-6818.4ppm and and values of LC90 range from 3667.3-17427.9ppm, respectively. The KDT50 range from 0.30 to 2.8% and KDT90 values range from1.2 to 110.8%, respectively. In conclusion, Justicia adhatoda may be effective for controlling populations of vector mosquito.

Por ser o vetor do vírus do Nilo Ocidental e da falaríase, o controle de Culex quinquefasciatus Say é provavelmente essencial. O tratamento com inseticida sintético parece ser mais eficaz para o controle dos mosquitos vetores. No entanto, esses produtos são tóxicos para o meio ambiente e organismos não visados. Consequentemente, o controle ecológico dos mosquitos vetores é necessário. Nesse sentido, o inseticida botânico parece mais produtivo. Portanto, a presente pesquisa teve como objetivo investigar a eficácia do extrato metanólico e de várias frações, incluindo n-hexano, acetato de etila, clorofórmio e fração aquosa, obtidos do extrato metanólico de Ailanthus altissima (Mill.) Swingle, Artemisia scoparia Waldst. & Kit. e Justicia adhatoda L. usando funil de separação contra os estágios larval, pupal e adulto de C. quinquefasciatus. As larvas e pupas de C. quinquefasciatus foram expostas a várias concentrações (31,25-1000 ppm) de extrato metanólico, e suas frações por 24 horas de período de exposição. Para o bioensaio knock-down (bioensaio de impregnação de papel de filtro), diferentes concentrações do extrato metanólico e suas várias frações (ou seja, 0,0625, 0,125, 0,25, 0,5 e 1 mg / mL) foram aplicadas por um período de exposição de 1 hora. Os resultados foram analisados estatisticamente usando desvio padrão, análise Probit e regressão linear. Os valores de R2 de larvas, pupas e adultos variaram de 0,4 a 0,99. Os valores de LC50 (concentração que causa 50% de mortalidade) para larvas de terceiro estádio tardio após 24 horas de período de exposição variaram de 93-1856,7 ppm, enquanto os valores de LC90 variaram de 424-7635,5ppm. Os valores de LC50 para pupas variaram de 1326,7-6818,4 ppm e os valores de LC90 variaram de 3667,3-17427,9 ppm, respectivamente. O KDT50 variou de 0,30 a 2,8% e os valores de KDT90 variaram de 1,2 a 110,8%, respectivamente. Por fim, a espécie J. adhatoda pôde ser eficaz para controlar populações de mosquitos vetores.

Evaluation of indigenous plants extracts for mosquitocidal activity against different stages of Culex quinquefasciatus say (Diptera: Culicidae)

Abstract Being vector of West Nile Virus and falariasis the control of Culex quinquefasciatus is likely to be essential. Synthetic insecticide treatment is looking most effective for vectors mosquito control. However, these products are toxic to the environment and non-target organisms. Consequently, ecofriendly control of vectors mosquito is needed. In this regard botanical insecticide is looking more fruitful. Therefore, the present research aimed to investigate the effectiveness of methanolic extract and various fractions, including, n-hexane, ethyl-acetate, chloroform, and aqueous fraction, obtained from methanolic extract of Ailanthus altissima, Artemisia scoparia, and Justicia adhatoda using separating funnel against larval, pupal, and adult stages of Culex quinquefasciatus. The larvae and pupae of Culex quinquefasciatus were exposed to various concentrations (31.25-1000 ppm) of methanolic extract and its fractions for 24 hours of exposure period. For knock-down bioassay (filter paper impregnation bioassay) different concentration of the methanolic extract and its various fractions (i.e. 0.0625, 0.125, 0.25, 0.5 and 1mg/mL) were applied for 1 hour exposure period. The results were statistically analysed using standard deviation, probit analysis, and linear regression. The R2 values of larvae, pupae, and adult range from 0.4 to 0.99. The values of LC50 (concentration causing 50% mortality) for late 3rd instar larvae after 24 hours exposure period range from 93-1856.7 ppm, while LC90 values range from 424 -7635.5ppm. The values of LC50for pupae range form 1326.7-6818.4ppm and and values of LC90 range from 3667.3-17427.9ppm, respectively. The KDT50 range from 0.30 to 2.8% and KDT90 values range from1.2 to 110.8%, respectively. In conclusion, Justicia adhatoda may be effective for controlling populations of vector mosquito.

Resumo Por ser o vetor do vírus do Nilo Ocidental e da falaríase, o controle de Culex quinquefasciatus Say é provavelmente essencial. O tratamento com inseticida sintético parece ser mais eficaz para o controle dos mosquitos vetores. No entanto, esses produtos são tóxicos para o meio ambiente e organismos não visados. Consequentemente, o controle ecológico dos mosquitos vetores é necessário. Nesse sentido, o inseticida botânico parece mais produtivo. Portanto, a presente pesquisa teve como objetivo investigar a eficácia do extrato metanólico e de várias frações, incluindo n-hexano, acetato de etila, clorofórmio e fração aquosa, obtidos do extrato metanólico de Ailanthus altissima (Mill.) Swingle, Artemisia scoparia Waldst. & Kit. e Justicia adhatoda L. usando funil de separação contra os estágios larval, pupal e adulto de C. quinquefasciatus. As larvas e pupas de C. quinquefasciatus foram expostas a várias concentrações (31,25-1000 ppm) de extrato metanólico, e suas frações por 24 horas de período de exposição. Para o bioensaio knock-down (bioensaio de impregnação de papel de filtro), diferentes concentrações do extrato metanólico e suas várias frações (ou seja, 0,0625, 0,125, 0,25, 0,5 e 1 mg / mL) foram aplicadas por um período de exposição de 1 hora. Os resultados foram analisados estatisticamente usando desvio padrão, análise Probit e regressão linear. Os valores de R2 de larvas, pupas e adultos variaram de 0,4 a 0,99. Os valores de LC50 (concentração que causa 50% de mortalidade) para larvas de terceiro estádio tardio após 24 horas de período de exposição variaram de 93-1856,7 ppm, enquanto os valores de LC90 variaram de 424-7635,5ppm. Os valores de LC50 para pupas variaram de 1326,7-6818,4 ppm e os valores de LC90 variaram de 3667,3-17427,9 ppm, respectivamente. O KDT50 variou de 0,30 a 2,8% e os valores de KDT90 variaram de 1,2 a 110,8%, respectivamente. Por fim, a espécie J. adhatoda pôde ser eficaz para controlar populações de mosquitos vetores.

Mosquito Larvicidal Potential of Tropical Seaweeds: Acetylcholinesterase Inhibitory Effects of Bryopsis pennata, Padina australis and Sargassum binderi on Aedes aegypti (L.) and Aedes albopictus Skuse

@#Introduction: Inhibition of the cholinesterase’s function leads to paralysis and death. This mechanism is served as a common mode of action of insecticide. The three tropical seaweeds, namely Bryopsis pennata, Padina australis and Sargassum binderi were reported for its potential mosquito larvicidal effect. In the present study, these seaweeds were evaluated for their potential as a cholinesterase inhibitor in the mechanism of larvicidal action. Methods: Acetylcholinsterase (AChE) inhibition assay was carried out based on the colorimetric method using a microplate reader. Phytochemical content of the seaweed extracts was screened by using liquid chromatography-mass spectroscopy (LC-MS). Results: Green seaweed B. pennata showed the strongest inhibition effect towards in vitro AChE by using tissue homogenates of Aedes aegypti (IC50 value = 0.84 mg mL-1) and Aedes albopictus as the enzyme source (IC50 value = 0.92 mg mL-1). The pattern of Lineweaver-Burk plots revealed that B. pennata was a mixed type inhibitor of AChE, as the readings of Km, Vmax, Ki and Ki’, indicates that it had a strong inhibition ability with high binding affinity towards both free enzyme and enzyme-substrate complex. Conclusion: These findings suggest the compound(s) in B. pennata extract serves as a promising source that could be developed into a mosquito larvicidal agent with AChE inhibition effect.

Phytochemical profiling and biological activity of Plectranthus amboinicus (Lour.) mediated by various solvent extracts against Aedes aegypti larvae and toxicity evaluation

Objective: To analyze the phytochemical compounds and to investigate the bio-toxic efficacy of various solvent extracts of Plectranthus amboinicus against mosquito larvae activity and lethality on non-targeting organisms. Methods: The methanol, ethyl acetate, hexane, and aqueous extracts of Plectranthus amboinicus were subjected to analyze the mosquitocidal activity against the dengue vector, Aedes aegypti and toxicity assays on zebra fish and brine shrimp. Three replications were performed, and negative control was also maintained. Amongst, ethyl acetate extract of Plectranthus amboinicus was chosen for the determination of bio-active compounds. Results: The mosquitocidal assays of methanol and ethyl acetate extracts of Plectranthus amboinicus showed the maximal activity with minimal concentration against the 4th instar mosquito-larvae of Aedes aegypti through the following lethal concentration (LC50 and LC90) values: 53.36 & 92.51 μg/mL and 13.64 & 86.09 μg/mL, respectively. In addition, the plant extracts showed no toxicity on zebra fish embryo and brine shrimp assays. The gas-chromatography analysis of the ethyl acetate extract of Plectranthus amboinicus revealed the presence of seven different compounds. Among them, PAEA-fraction 60 contained a major active bioactive compound, hexadecanoic acid, methyl ester (270.0). Conclusions: Plectranthus amboinicus possesses mosquitocidal properties and could be used as a potential alternative source for preparing the mosquitocidal agents.

Phytochemical profiling and biological activity of Plectranthus amboinicus (Lour.) mediated by various solvent extracts against Aedes aegypti larvae and toxicity evaluation

Objective: To analyze the phytochemical compounds and to investigate the bio-toxic efficacy of various solvent extracts of Plectranthus amboinicus against mosquito larvae activity and lethality on non-targeting organisms. Methods: The methanol, ethyl acetate, hexane, and aqueous extracts of Plectranthus amboinicus were subjected to analyze the mosquitocidal activity against the dengue vector, Aedes aegypti and toxicity assays on zebra fish and brine shrimp. Three replications were performed, and negative control was also maintained. Amongst, ethyl acetate extract of Plectranthus amboinicus was chosen for the determination of bio-active compounds. Results: The mosquitocidal assays of methanol and ethyl acetate extracts of Plectranthus amboinicus showed the maximal activity with minimal concentration against the 4th instar mosquito-larvae of Aedes aegypti through the following lethal concentration (LC50 and LC90) values: 53.36 & 92.51 μg/mL and 13.64 & 86.09 μg/mL, respectively. In addition, the plant extracts showed no toxicity on zebra fish embryo and brine shrimp assays. The gas-chromatography analysis of the ethyl acetate extract of Plectranthus amboinicus revealed the presence of seven different compounds. Among them, PAEA-fraction 60 contained a major active bioactive compound, hexadecanoic acid, methyl ester (270.0). Conclusions: Plectranthus amboinicus possesses mosquitocidal properties and could be used as a potential alternative source for preparing the mosquitocidal agents.

Pouteria campechiana leaf extract and its bioactive compound myricitrin are mosquitocidal against Aedes aegypti and Culex quinquefasciatus

Objective: To test the mosquitocidal potential of leaf extracts of Pouteria campechiana prepared with different solvents and elucidate the structure of an isolated mosquitocidal compound. Methods: The leaf extracts of Pouteria campechiana prepared with three solvents (petroleum benzene, ethyl acetate and acetone) and potential bioactive fractions were tested against various stages of Aedes aegypti and Culex quinquefasciatus by using the WHO protocols, and the chemical profile and its functional groups were identified by GC-MS and Fourier transmission-infrared spectroscopy (FT-IR). The structure of bioactive compound was characterized by nuclear magnetic resonance (NMR) spectral technique. Results: The preliminary phytochemical results revealed the presence of alkaloids, amino acids, flavonoids, quinones, saponins, steroids, tannins, and terpenoids in the acetone extract. A significant toxic potential was observed in the acetone extract against both Aedes aegypti and Culex quinquefasciatus mosquitoes. The acetone extract exhibits remarkable larvicidal (LC50: 12.232 μg/mL and LC90: 63.970 μg/mL), pupicidal (LC50: 18.949 μg/mL and LC,0: 167.669 μg/mL) and adulticidal (LC50: 20.689 μg/mL and LC90: 72.881 μg/mL) effects against Aedes aegypti. Furthermore, the same extract was subjected to isolation of bioactive compound by GC- MS and FT-IR analysis. GC-MS results showed the presence of 5 major compounds, and octacosane (18.440%) was detected as the predominant compound. The FT-IR result of acetone extract demonstrated the presence of various functional groups like alkanes/alkynes, ester, aromatic and amides. The NMR spectrum results of isolated compound were well matched to glycoside linked flavonoids. Based on the chromatography and spectral techniques the isolate molecule was identified as myricitrin by FT-IR and nuclear magnetic resonance spectral data. Conclusion: The isolated compound myricitrin possesses a significant toxic effect in all stages of Aedes aegypti and Culex quinquefasciatus mosquito's with lowest LC50 and LC90 values.

Pouteria campechiana leaf extract and its bioactive compound myricitrin are mosquitocidal against Aedes aegypti and Culex quinquefasciatus

Objective: To test the mosquitocidal potential of leaf extracts of Pouteria campechiana prepared with different solvents and elucidate the structure of an isolated mosquitocidal compound. Methods: The leaf extracts of Pouteria campechiana prepared with three solvents (petroleum benzene, ethyl acetate and acetone) and potential bioactive fractions were tested against various stages of Aedes aegypti and Culex quinquefasciatus by using the WHO protocols, and the chemical profile and its functional groups were identified by GC-MS and Fourier transmission-infrared spectroscopy (FT-IR). The structure of bioactive compound was characterized by nuclear magnetic resonance (NMR) spectral technique. Results: The preliminary phytochemical results revealed the presence of alkaloids, amino acids, flavonoids, quinones, saponins, steroids, tannins, and terpenoids in the acetone extract. A significant toxic potential was observed in the acetone extract against both Aedes aegypti and Culex quinquefasciatus mosquitoes. The acetone extract exhibits remarkable larvicidal (LC

Downstream processing of mosquitocidal toxins from solid state fermentation of Lysinibacillus sphaericus and Bacillus thuringiensis israelensis

Aims: The aim of this study was downstream processing of moquitocidal toxins produced by Lysinibacillus sphaericus (L. sphaericus) and Bacillus thuringiensis israelensis (Bti) under solid state fermentation. Methodology and results: Two mosquitocidal strains (L. sphaericus and Bti) were grown separately in trays under solid state fermentation for toxin production. The best conditions for extraction of crude toxins from fermented solids of both cultures were tap water at 5-50 °C, for 10 min under static conditions. Also, concentrated mosquitocidal toxins were efficiently extracted from fermented solids by 4 constitutive additions of 500 mL tap water to 1 kg of fermented culture at room temperature (25 °C) for 5 min each under static conditions. Both extracted toxins were formulated with talcum powder and they were stable for 8 months at room temperature. Conclusion, significance and impact of study: It is very important to study the operating conditions for mosquitocidal toxins extraction from solid state fermentation (SSF) and its formulation in cost effective manner.

Characterization and Virulence of an Indigenous Soil Bacillus sp. Prospecting for Mosquito Control.

Aims: Aquatic habitat of the rice fields is the effective breeding site of the mosquitoes whose overcrowding would promote their pathogens. But no attention has been paid to these habitats for isolation and identification of the bacterial biocides. Therefore, the study was envisaged to isolate and identify the mosquitocidal bacteria from the unexplored rice field soil of the Burdwan district (a premier rice producer), West Bengal, India. It was also aimed to evaluate the virulence of the potent pathogenic organisms in the laboratory and field against the mosquitoes. Study Design: Laboratory and field study. Place and Duration of the Study: Parasitology and Microbiology Research Laboratory, Department of Zoology, The University of Burdwan, Burdwan 713104, West Bengal, India and Microbiology Laboratory, Crop Production Division, Central Rice Research Institute, Cuttack 753 006, Orissa, India. The study was conducted between June, 2011 to July 2012. Methodology: The soils were collected from the rice-fields, serially diluted up to 10-3 level, 100 μl suspension was plated on NA medium and incubated at 30±0.1ºC in the BOD incubator for 72 h. The colonies were checked under a phase-contrast microscope and those having spores were purified by dilution plating on NA plates. Phenotypic, biochemical and molecular characters of the bacteria were studied following standard methods. The mosquitocidal activity of the selected organism was assessed using different mosquito species both in the laboratory and field. Results: On the basis of phenotypic, biochemical and 16S rDNA (Acc. no. GU190368) analysis, the selected bacteria (Ts 116) was identified as Bacillus sp. In the laboratory, the LC50s of the Bacillus sp. Ts116 against late third instar larvae of An. subpictus, Ar. subalbatus and Cx. quinquefasciatus were (2.37, 2.2 and 9.6) X 106 bacteria/ml, respectively. After 7d, treatment with 100 ml suspension (containing 2.7x106 bacteria/ml) of bacteria/m3 breeding site effected 97.35, 95.65 and 100% mortality of An. subpictus, Ar. subalbatus and Cx. quinquefasciatus larvae, respectively. Conclusion: Indiscriminate use of chemical insecticides causes vector-resistance resulting in serious health and environmental hazards. The Bacillus sp. Ts116 (GU190368) of the rice fields had potential to be exploited in mosquito control programms.

Mosquitocidal Bacillus amyloliquefaciens: Dynamics of growth & production of novel pupicidal biosurfactant.

Background & objectives: A strain of Bacillus amyloliquefaciens (VCRC B483) producing mosquito larvicidal and pupicidal biosurfactant was isolated from mangrove forest soil. The present study was aimed at studying the kinetics of growth and production of the mosquitocidal biosurfactant by this bacterium. Methods: Dynamics of growth, sporulation and production of mosquitocidal biosurfactant were studied by standard microbiological methods. The mosquitocidal biosurfactant was precipitated from the culture supernatant and bioassayed against immature stages of   mosquito vectors to determine lethal dose and lethal time. The activity, biological and biochemical properties of the biosurfactant have also been studied. Results: The pupal stages of mosquitoes were found to be more vulnerable to the biosurfactant produced by this bacterium with Anopheles stephensi being the most vulnerable species. The median lethal time (LT50) was found to be 1.23 h when the pupal stages of the above species were exposed to lethal concentration LC90 (9 μg/ml) dosage of the biosurfactant. Production of biosurfactant was found to increase with incubation time and maximum biomass, maximum quantity of biosurfactant (7.9 mg/ml), maximum biosurfactant activity (6 kBS unit/mg) and maximum mosquitocidal activity (5 μg/ml) were attained by 72 h of growth. The lipopeptide nature of the biosurfactant was confirmed by β-haemolysis, lipase activity, biofilm forming capacity, thermostability and biochemical analysis. Interpretation & conclusions: The mosquitocidal biosurfactant produced by B. amyloliquefaciens (VCRC B483) may be a prospective alternative molecule for use in mosquito control programmes involving bacterial biopesticides.

Enhanced production of mosquitocidal cyclic lipopeptide from Bacillus subtilis subsp. subtilis.

Background & objectives: A cyclic lipopeptide, surfactin produced by a strain of Bacillus subtilis subsp. subtilis (VCRC B471) was found to exhibit activity against both the larval and pupal stages of mosquitoes. The present study was aimed at increasing the production of the mosquitocidal metabolite by modifying the conventional medium. Methods: Enhancement of mosquitocidal metabolite production was attempted by replacing the existing micronutrients of the conventional NYSM and supplementing the medium with additional amounts of glucose. The LC50 value of culture supernatant (CS) against the larval and pupal stages of Anopheles stephensi was determined. Crude mosquitocidal metabolite (CMM) was separated from the CS, identified by MALDI-TOF analysis and its LC50 dosage requirement for the pupal stage of the above mosquito species determined. Results: The medium containing a new composition of micronutrients and glucose up to 1 per cent resulted in increased metabolite production. The LC50 value of the CS obtained in the improved medium against larvae and pupae of An. stephensi was 5.57 and 0.71 μl/ml, respectively. The yield of CMM was doubled in the improved medium. MALDI-TOF analysis revealed that the CMM was surfactin. Interpretation & conclusions: The new improved medium enhanced the production of mosquitocidal metabolite as the dosage required for inciting 50 per cent mortality among the pupal stages of mosquitoes was only half of that required when the metabolite was produced in the conventional medium. The mosquitocidal metabolite was identified as surfactin, a cyclic lipopeptide and biosurfactant.

Tagetes erecta Linn. and its mosquitocidal potency against Culex quinquefasciatus

<p><b>OBJECTIVE</b>To investigate mosquitocidal effects of ethanolic extract of flowers of Tagetes erecta (T. erecta) and its chloroform and petroleum ether soluble fractions against the larvae of Culex quinquefasciatus (Cx. quinquefasciatus).</p><p><b>METHODS</b>The fresh flowers of T. erecta were extracted in cold with ethanol (5.0 L) and after concentration, the ethanol extract was fractionated with chloroform and petroleum ether to afford a brownish syrupy suspension of ethanol extract (50.0 g), petroleum ether soluble fraction (18.6 g) and chloroform soluble fraction (23.8 g). The larvicidal effect of ethanol extract and their solvent fractions were determined by the standard procedure of WHO against different instars of Cx. quinquefasciatus.</p><p><b>RESULTS</b>Among the tested samples the chloroform soluble fractions showed the highest toxicity and consequently, the lowest LC50 values (14.14 µg/mL, 17.06 µg/mL, 36.88 µg/mL and 75.48 µg/mL) for all the instars larvae of Cx. quinquefasciatus. The larvae showed comparative tolerance in the course of increasing age and time.</p><p><b>CONCLUSIONS</b>It can be concluded that the flowers of T. erecta are very effective natural larvicide and could be useful against Cx. quinquefasciatus.</p>

Preliminary study on mosquito repellent and mosquitocidal activities of Ocimum gratissimum (L.) grown in eastern Nigeria.

Background & objectives: The study examined the mosquito-repellent and mosquitocidal activities of the volatile oil of Ocimum gratissimum at three different locations (World Bank Estate, Ihitte and Umuekunne) in Imo State, eastern Nigeria, with the purpose of sourcing for mosquito repellent that is cheap, abundant, environment and user-friendly. Methods: Four different lotions; 20% (v/v) and 30% (v/v) concentrations each of the extracted volatile oil in two natural oil bases (olive and palm kernel) were made and six volunteered human baits were used to evaluate the mosquito repellent and mosquitocidal activities of the stock materials at the three different centres from September to November 2008. Results: Topical application of each of the four different lotions significantly (p <0.05) reduced the biting rate of mosquitoes in all the three locations tested. The 30% (v/v) concentration in olive oil base exhibiting highest average percentage repellencies of 97.2, 95.7 and 96.3% at World Bank Estate, Ihitte and Umuekunne centres respectively while the 20% (v/v) concentration in palm kernel oil base had the least repellency of 36.3, 41.6 and 36.3%, respectively. The other two formulations had values ranging from 67.8 to 80% in the three locations. The 30% (v/v) concentration in both olive and palm kernel oil bases afforded all night protection against mosquito bites in all the centres, and demonstrated fast knockdown and paralyzing effect on few mosquitoes at the urban centre (World Bank Estate). Interpretation & conclusion: The study confirms that O. gratissimum grown in eastern Nigeria has mosquito-repellent and mosquitocidal potentials and the formulations could be used to reduce human-mosquito contacts and hence mosquito-borne diseases and irritations caused by their bites.