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The essential oil of the aerial parts of Chenopodium ambrosioides L. has been isolated by hydrodistillation and analyzed using GC-MS. The major components were found to be α-terpinene (63.1%), p-cymene (26.4%) and ascaridole (3.9%). The oil displayed no antibacterial activity against either Gram-positive bacteria Bacillus cereus or Staphylococcus aureus, or the Gram-negative bacterium Escherichia coli (MIC = 1250 µg/mL). A cluster analysis of C. ambrosioides essential oils reveals at least seven distinct chemotypes: ascaridole, α-terpinene, α-pinene, p-cymene, carvacrol, α-terpinyl acetate, and limonene.

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In the course of our search for new insect antifeedant substances from plants, we have devised an improved antifeedant leaf‐disk bioassay. Our system allows an accurate measurement of consumed disk surfaces, using a video camera interfaced with a computer. The scanned image of the leaf disks is stored, and the eaten areas are measured with the help of a video‐image analysis software. This new method allows for precise quantification of insect antifeedant activity tested on leaf material. This method was applied to the screening of Hokkaido plants for antifeedant activity. Out of 206 samples, seven demonstrated significant activity against larvae of the tobacco cutworm, Spodoptera litura.

Bioassay-guided isolation of bioactive natural substances requires monitoring of all fractionation and purification steps using a bioassay system. This is often a long and tedious process, especially with insect feeding bioassays. We report here a new method, based on the principle of bioautography, for a quick isolation of insect antifeedant compounds. TLC plates, after development, are coated with a thin layer of artificial diet and fed toSpodoptera litura larvae. The location of uneaten areas is then compared with theR fvalues of the TLC spots, in order to determine rapidly the active fractions. This methods allows for a very fast determination of the most active antifeedant compounds in a complex mixture and considerably speeds up the isolation process. This new method was successfully applied in the study of antifeedant activity of several plant samples, and results are presented here for a model plant,Skimmia japonica (Rutaceae). Using this new method, the compounds responsible for the feeding-deterrent activity, three furanocoumarins (bergapten, xanthotoxin, and oxypeucedanin), were quickly and efficiently identified.

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