Bioactivity of Acyranthes aspera (Amaranthaceae) Foliage against the Japanese Encephalitis Vector Culex vishnui Group
Mosquito and Microbiology Research Units, Parasitology Laboratory, Department of Zoology, The University of Burdwan, Burdwan-713104, West Bengal, India
Journal of Mosquito Research, 2013, Vol. 3, No. 13 doi: 10.5376/jmr.2013.03.0013
Received: 24 Sep., 2013 Accepted: 10 Oct., 2013 Published: 05 Nov., 2013
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Preferred citation for this article:
Kuntal Bhattacharya and Goutam Chandra, 2013, Bioactivity of Acyranthes aspera (Amaranthaceae) Foliage against the Japanese Encephalitis Vector Culex vishnui Group, Journal of Mosquito Research, Vol.3, No.13 89-96 (doi: 10.5376/jmr.2013.03.0013)
Background and objective: Failure to develop proper vaccines against mosquito borne diseases, a global health problem, imposes sole reliance on the vector managerial steps for reducing the disease incidences. Easy abundance, cost effectiveness, target specificity as well as bio-degradability of botanicals draw the most attention as vector control agents than their synthetic counterparts which facilitate vector resistance and intoxicate natural resources. The present study estimated larvicidal activities of the crude and solvent extracts of Acyranthes aspera against the vector of Japanese encephalitis Culex vishnui group under laboratory conditions.
Methods: Crude extracts of A. aspera foliage ranging from 0.1% to 0.5% concentrations were examined for larvicidal activity against 1st to 4th instars larvae of Cx. vishnui group. Extractions of the active fractions were carried out by means of six different solvents in a non-polar to polar approach viz. petroleum ether, n-hexane, ethyl acetate, chloroform: methanol (1:1 v/v), acetone, and absolute alcohol. Dose dependent mortality was established through graded concentrations ranging from 20 ppm to 100 ppm using the bioactive fractions. Further, determinations of LC50 and LC90 values of crude and bioactive fractions were accomplished through log-probit analyses. Statistical justifications of the larvicidal property were established through ANOVA analyses regarding instars, time and concentrations as three completely randomized independent variables. Costing impacts on the non-target water fauna of the bio-active portion were assessed under laboratory conditions.
Result: In a 72 hour bioassay experiment with crude extract, the highest mortality was recorded in 0.5% concentration. Acetone extractive was found to exert efficient larvicidal activity amongst all the solvent extractives. Cent per cent mortalities were exhibited by 1st and 2nd instars larvae at 48 hours of exposure while 3rd instars larvae showed 97.32% mortality at 72 hours of exposure with LC50 value of 32.15 ppm. An obvious dose-dependent mortality was established through regression analyses, as the rate of mortality (Y) was positively correlated with the concentration (X). The non-target populations were primarily non-responsive to plant extracts under study.
Conclusion: Extract of A. aspera foliage is of great consequence having appreciable larvicidal activity against Cx. vishnui group. The compound is environment friendly and largely non-toxic to non-target organisms.
Acyranthes aspera; Larvicide; Culex vishnui group; Non-target organism