Isolation and Identification of Mosquito Biting Deterrent and Larvicidal Compounds from Veratrum lobelianum Roots

There has been renewed interest in finding a use for natural plant extracts as alternative sources for public health pesticides since these extracts and their constituent compounds are normally considered safer than chemicals for human health and the environment. In this respect, medicinal and aromatic plants from the National Center for Natural Products Research repository were evaluated for anti-mosquito activity against Aedes aegypti. Based on the screening results, the ethanolic extract of Veratrum lobelianum Bernh. roots showed the most potent larvicidal activity with LD₅₀ value of 11.35 (9.27 – 13.85) ppm against 1 day old Ae. aegypti larvae. It also showed good biting deterrent activity against adult female Ae. aegypti. Systematic bioassay-guided fractionation of V. lobelianum root extract was performed to identify active larvicidal and biting deterrent compounds. Out of the six sub-fractions (A-F), only A, B and C showed larvicidal activity and only sub-fraction B demonstrated biting deterrent activity. The selective active sub-fractions were subjected to column chromatography and active compounds, two stilbenoids, one phytosterol and two fatty acid methyl esters were isolated and individually tested in the dose response bioassays. The structure elucidation was achieved by NMR data analyses. Acknowledgements. This study was supported by USDA, ARS grant No. 56 – 6402 – 1-612 and Deployed War-Fighter Protection (DWFP) Research Program and the U.S. Department of Defense through the Armed Forces Pest Management Board (AFPMB).