Abstract
Background Vector control is facing a menace due to the appearance of resistance to synthetic insecticides. Insecticides of plant origin may provide appropriate substitute biocontrol techniques in the future. The present study was carried out to investigate the bio control potentiality of active ingredient isolated from chloroform: methanol (1:1 v/v) extract of mature leaves of Solanum nigrum L. (Solanaceae) against early 3rd instar larvae of Culex vishnui group (comprising of Cx. vishnui Theobald, Cx. pseudovishnui Colless and Cx. tritaeniorhynchus Giles) and Anopheles subpictus Grassi. S. nigrum is a common plant distributed in many parts of India with medicinal properties.Methods Bioactive compound isolated from chloroform: methanol (1:1 v/v) extract of mature leaves of S. nigrum was (25, 45, 60 mg/L) tested against early 3rd instar larvae of Cx. vishnui group and An. subpictus. The lethal concentration was determined by log probit analysis. The chemical nature of the active substance was also evaluated following gas chromatography–mass spectroscopy (GC–MS) and infrared (IR) analysis. The compound was also studied on non target organisms such as Daphnia sp. and Diplonychus annulatum.ResultsTLC spot having Rf value of 0.94 (Rf = 14.1/15 = 0.94) showed larvicidal activity. In a 72 h bioassay experiment, mortality rate at 60 mg/L was significantly higher (P < 0.05) than those at 25 and 45 mg/L against early 3rd instar. Result of log-probit analysis (at 95% confidence level) revealed that LC50 and LC90 values gradually decreased with the exposure period showing the lowest value at 72 h of exposure. A clear dose-dependent mortality was observed, as the rate of mortality (Y) was positively correlated with the concentration (X) having regression coefficient value close to one in each case. The compound was found to be eco-friendly as it did not show any adverse effect to the studied non target organisms. Chemical characterization (GC–MS and IR analyses) of the active ingredient revealed the presence of phytosteroid compounds responsible for mosquito larvicidal activity.ConclusionLeaf extract of S. nigrum has great potential as bio control agent against Cx. vishnui group and An. subpictus. In near future the isolated bioactive phytochemical could be used as a source of an effective mosquitocidal agent.
Highlights
Vector control is facing a menace due to the appearance of resistance to synthetic insecticides
The disease is caused by Japanese encephalitis (JE) virus (JEV), which belongs to the family Flaviviridae and transmitted by Culex vishnui group which are the main vectors of JE in different parts of India
The plant products or plant-derived compounds are promising alternatives to synthetic insecticides in controlling insect pests of medical importance as these are environmentally safe, biodegradable, of low cost and may be produced using indigenous methods, for vector control [10,11,12,13,14] and can be used with minimum care by individual and communities [15]. Some herbal products such as nicotine obtained from tobacco leaves; anabasine and lupinine, the alkaloids extracted from Russian weed, Anabasis aphylla [15], rotenone from Derris eliptica [16] and pyrethrums from Chrysanthemum cinererifolium flowers [17] have been used as natural insecticides earlier
Summary
Vector control is facing a menace due to the appearance of resistance to synthetic insecticides. The plant products or plant-derived compounds are promising alternatives to synthetic insecticides in controlling insect pests of medical importance as these are environmentally safe, biodegradable, of low cost and may be produced using indigenous methods, for vector control [10,11,12,13,14] and can be used with minimum care by individual and communities [15] Some herbal products such as nicotine obtained from tobacco leaves; anabasine and lupinine, the alkaloids extracted from Russian weed, Anabasis aphylla [15], rotenone from Derris eliptica [16] and pyrethrums from Chrysanthemum cinererifolium flowers [17] have been used as natural insecticides earlier. Kishore et al [18]. and Ghosh et al [19]. have reviewed the present status on the efficacy of plant extracts in the mosquito control study
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