Novel antifeedant and insecticidal compounds from avocado idioblast cell oil

Several insecticidal compounds have been identified by bioassaydriven fractionation of avocado, Persea americana Mill, idioblast cell oil. A flash chromatography fraction of the oil showed substantial toxicity to early instars of the generalist insect herbivore, Spodoptera exigua (Hubner) (100% mortality after seven days). Following further fractionation, five biologically active compounds, 2-(pentadecyl)furan, 2-(heptadecyl)furan, 2-(1E-pentadecenyl)furan, 2-(8Z, 11Z-heptadecadienyl)furan, and the triglyceride triolein, were identified. Several minor components were also tentatively identified, including 2-(1Z-pentadecenyl)furan, 2-(1E-heptadecenyl)furan, and 2-(1E,8Z, 11Z-heptadecatrienyl)furan. Several 2-alkylfurans of this type have been reported previously from avocado (Persea spp.) and have received the common name of avocadofurans. The major compounds were tested individually for toxic and growth inhibitory effects. Individually, the compounds had low to moderate toxicity. Of these, 2-(pentadecyl)furan had the greatest effects, with an LC₅₀ value of 1031 μg/g. At concentrations of 600 μg/g or higher in diets, larval growth was inhibited by >70% compared to controls. The analogous 2-(heptadecyl)furan had an LC₅₀ value of 1206 μg/g, and also significantly reduced larval growth (>75% versus controls) at concentrations of > 600 μg/g. The unsaturated analogs 2-(1E-pentadecenyl)furan and 2-(8Z, 11Z-heptadecadienyl)furan were less toxic. Triolein was only weakly toxic, with an LC₅₀ value of 10,364 μg/g diet. Larval growth was inhibited only at concentrations of 7000 μg/g or higher. The potential of avocadofurans in insect control is discussed.