Larvicidal potential of different solvent extracts and oleanolic acid derivative from Coccinia indica against vector mosquitoes

Abstract

The mosquito larvicidal activities of different solvent extracts (chloroform, ethyl acetate, and methanol) from the leaves of Coccinia indica were studied. Among the extracts tested, the methanol extract showed the highest larvicidal activity against early fourth instar larvae of Culex quinquefasciatus (LC₅₀ = 142 mg L⁻¹), Aedes aegypti (LC₅₀ = 158 mg L⁻¹) and Anopheles stephensi (LC₅₀ = 161 mg L⁻¹) after 24 h of exposure period. The lowest larval mortality was observed with the ethyl acetate extract with the LC₅₀ values of 927, 872, and 730 mg L⁻¹ against Cx. quinquefasciatus, Ae. aegypti, and An. stephensi, respectively. The chloroform extract showed the moderate larvicidal activity against the mosquito species tested with the LC₅₀ values from 446 to 546 mg L⁻¹. A new triterpene was isolated from the methanol extract using bio-assay guided separation and identified as an oleanolic acid derivative by NMR, IR and mass spectral studies. The compound showed prominent larvicidal activity against Cx. quinquefasciatus, Ae. aegypti and An. stephensi with the LC₅₀ values of 5.6, 5.0, and 4.8 mg L⁻¹, respectively. The results of the present investigation offer an opportunity for developing alternatives to rather expensive and environmentally hazardous organic insecticides.

Keywords:

• Coccinia indica
• triterpene derivative
• mosquito larvicidal activity

Acknowledgments

Defence Research and Development Establishment, DRDO (Ministry of Defence, Government of India), Gwalior is gratefully acknowledged for financial support (Grant No. TC/05414-Proj/Task-108/2009). The authors are also thankful to Dr R. Panneerselvam, Professor and Head, Department of Botany, Annamalai University for providing laboratory facilities.