Vol. 3, Issue 2, Part A (2016)

Author(s): Subramanian Arivoli, Samuel Tennyson, Rajasingh Raveen, Manickkam Jayakumar, Balasubramanian Senthilkumar, Marimuthu Govindarajan, Ranganathan Babujanarthanam, Selvaraj Vijayanand

Abstract: Mosquito control, in view of their medical importance, assumes global importance. In the context of ever increasing trend to use more powerful synthetic insecticides to achieve immediate results in the control of mosquitoes, an alarming increase of physiological resistance in the vectors and its increased toxicity to non-target organism are noteworthy. This has led to intensified search for tools that demonstrate eco-friendliness and target specificity. Phytochemicals are botanicals which are naturally occurring insecticides obtained from floral resources. In the quest for alternative natural biological control agents against mosquito larvae, the present paper reports on the larvicidal activity of fractions of Sphaeranthus indicus ethyl acetate whole plant extract against vector mosquitoes viz., Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. Nine fractions viz., A, B, C, D, E, F, G, H and I were obtained from the residue of ethyl acetate extract by column chromatography. Standard WHO protocols with minor modifications was adopted for the larvicidal bioassay. Larvicidal activity was evaluated at concentrations of 25, 50, 75 and 100 ppm. Larval mortality was observed 24 hours after treatment. Amongst the fractions tested, fraction ‘F’ showed one hundred per cent mortality against third instar larvae of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus at 100 ppm and LC₅₀ values were 36.76, 26.85 and 32.60 ppm respectively. In conclusion, the bioassay result of the present study indicated the larvicidal property against vector mosquitoes of fractions of Sphaeranthus indicus ethyl acetate whole plant extract, especially for the ‘F’ fractionated group. Future research to extract a pure compound of the active fractionated group should be explored to find a new highly efficient larvicidal substance.

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