Mosquitocidal activity of acetylenic compounds from Cryptotaenia canadensis

As part of an on-going program to identify natural products from plants with mosquitocidal activity, two acetylenic compounds were isolated from Cryptotaenia canadensis, a native North American umbellifer frequently encountered in moist woodlands. Fresh foliage, roots, and fruits were extracted with a hot methanol and water mixture and then dried. The extract was partitioned into chloroform and water, and both phases were bioassayed against fourth instars of Culex pipiens at concentrations between 5 and 50 ppm. Only the organic phase was active. Gas-liquid chromatography revealed that the two main components of the organic phase were polyacetylenes. The compounds were isolated by vacuum chromatography on silica gel and identified as falcarinol and falcarindiol based on GC-MS-EI and GC-MS-CI fragmentation patterns, high-resolution MS, and H-1 and C-13 NMR spectrometric data. The dose-response curves with mosquito larvae were determined by probit analysis. The LC50 values were 3.5 ppm for falcarinol and 6.5 ppm for falcarindiol. The distribution of polyacetylenes varied among plant parts. Fruits contained an unknown compound not found in either the foliage or roots.