Silphinene sesquiterpenes as model insect antifeedants

Area of Science:

• Natural Products Chemistry
• Insect Chemical Ecology
• Organic Synthesis

Background:

• Silphinene sesquiterpenes are known insect antifeedants, particularly effective against chrysomelid beetles.
• Insect GABA receptors are crucial targets for neuroactive compounds, including natural and synthetic pesticides.
• Understanding structure-activity relationships of sesquiterpenes can lead to novel pest control strategies.

Purpose of the Study:

• To synthesize and evaluate a series of silphinene analogs for their insect antifeedant properties.
• To compare the efficacy of silphinene analogs with known GABA-antagonists and modulators like picrotoxinin and thymol.
• To investigate the species-specific toxicity and feeding ecology correlations of these compounds.

Main Methods:

• Synthesis of nine silphinene analogs and one presilphiperfolane sesquiterpene.
• Antifeedant bioassays conducted on diverse insect species: Spodoptera littoralis (Lepidoptera), Leptinotarsa decemlineata (Chrysomelidae), and five aphid species.
• Comparative analysis of antifeedant activity against picrotoxinin and thymol, with toxicity assessments.

Main Results:

• All tested insect species exhibited antifeedant responses to at least one silphinene analog or GABA antagonist.
• Compound 3 (11beta-acetoxy-5alpha-isobutyryloxysilphinen-3-one) and thymol demonstrated broad-spectrum antifeedant activity, excluding S. littoralis.
• Antifeedant potency varied based on insect feeding ecologies, and compound toxicity was species-dependent, not correlating with antifeedant effects.

Conclusions:

• Silphinene analogs, particularly compound 3, represent promising leads for developing new insect antifeedants.
• GABA receptor modulation is a viable mechanism for controlling a wide range of insect pests.
• Further research into species-specific interactions and toxicity profiles is warranted for practical applications.