Composition of Prangos pabularia Essential Oil: Identification of an Unknown Compound from the Oil and its Insecticidal Activity against Yellow Fever Mosquito, Aedes aegypti

The essential oil of air dried fruits of Prangos pabularia Lindl (Apiaceae) was obtained by hydrodistillation and its chemical profile was determined using GC-FID and GC-MS. Bicyclogermacrene (21%), (Z)-β-ocimene (19%), α-humulene (8%), α-pinene (8%) and spathulenol (6%) were the main constituents of the oil. The identification of the separated volatile organic compounds was accomplished through comparison of mass spectra of peaks with those stored in the in-house “Baser Library of Essential Oil Constituents.” Additional confirmation was achieved by comparison of retention indices from compound peaks. From inspection of chromatograms in the GC-MS analysis, there was an unknown compound at RI 2931 with a mass spectrum similar to suberosin in the Wiley GC-MS Library. Since this compound was not present in the Baser Library, we could only tentatively identify this compound based on similarity of the mass spectrum to the one in the Wiley GC/MS Library. Due to insufficient oil yield, we synthesized suberosin in two steps and confirmed its structure by 1D NMR and GC-MS analyses. As part of our continued research to discover botanical insecticides for use in mosquito control as repellent and larvicides, suberosin was investigated for mosquito biting deterrent and larvicidal activity against Aedes aegypti. Suberosin showed good but lower biting deterrent than DEET (N,N-diethyl-m-toluamide). In larval bioassays, suberosin had good activity against 1-d-old Ae. aegypti larvae. These results indicate that this compound may be useful as a mosquito control agent. 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).