Larvicidal activity of phytosteroid compounds from leaf extract of Solanum nigrum against Culex vishnui group and Anopheles subpictus.
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.


RESULTS
TLC spot having Rfvalue 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 LC50and LC90values 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.


CONCLUSIONS
Leaf 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.
Department of Zoology, University of Gour Banga, Malda, West Bengal, 732103, India.
Anjali
A
Rawani
Mosquito, Microbiology and Nanotechnology Research Units, Parasitology Laboratory, Department of Zoology, The University of Burdwan, Golapbag, Burdwan, West Bengal, 713104, India.
Anushree Singha
AS
Ray
Department of Zoology, Bankura Christian College, Bankura, West Bengal, 722101, India.
Anupam
A
Ghosh
Department of Biochemistry, Indian Institute of Science, Bangaluru, Karnataka, 560012, India.
Mary
M
Sakar
Mosquito, Microbiology and Nanotechnology Research Units, Parasitology Laboratory, Department of Zoology, The University of Burdwan, Golapbag, Burdwan, West Bengal, 713104, India. goutamchandra63@yahoo.co.in.
Goutam
G
Chandra
D000818:Animals; D000852:Anopheles / Q000254:growth & development*; D002725:Chloroform / Q000737:chemistry; D002855:Chromatography, Thin Layer; D003465:Culex / Q000254:growth & development*; D008401:Gas Chromatography-Mass Spectrometry; D007306:Insecticides / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D007928:Lethal Dose 50; D000432:Methanol / Q000737:chemistry; D010840:Phytosterols / Q000494:pharmacology*; D010936:Plant Extracts / Q000494:pharmacology; D018515:Plant Leaves / Q000737:chemistry*; D032324:Solanum nigrum / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
D007306:Insecticides; D010840:Phytosterols; D010936:Plant Extracts; D002725:Chloroform; D000432:Methanol
Anopheles subpictus; Culex vishnui group; Mosquito control; Phytosteroid; Solanum nigrum