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Insecticidal activity of hypericin towardsManduca sexta larvae
1School of Biological Sciences, University of Bath, BA2 7AY, Claverton Down, Bath Avon, UK.
Journal of Chemical Ecology
|November 26, 2013
Summary
Hypericin (HYP) is toxic to Manduca sexta larvae, especially under light. This photodynamic quinone stunts growth and causes mortality, with toxicity dependent on light exposure and wavelength.
Area of Science:
- Toxicology
- Insect toxicology
- Photochemistry
Background:
- Hypericin (HYP) is a photodynamic quinone found in plants of the genus Hypericum.
- Photodynamic compounds can exhibit toxicity upon light activation.
Purpose of the Study:
- To investigate the toxic effects of hypericin (HYP) on Manduca sexta third-instar larvae.
- To determine the dose-dependent toxicity and light dependency of hypericin.
Main Methods:
- Determined the LD50 of purified hypericin in constant light.
- Assessed the effect of reduced irradiance on mortality.
- Investigated the impact of sublethal HYP doses on larval growth.
- Examined the role of light wavelength and pre-irradiation darkness on toxicity.
Main Results:
- The LD50 of hypericin was 16 μg/g larval weight under constant light (22 W/m(2)).
- Reduced light intensity decreased mortality, and toxicity was light-dependent (>500 nm).
- Sublethal HYP doses caused dose-dependent growth retardation.
- Phototoxicity was lost after >8 hours in darkness but retained if larvae were starved prior to irradiation.
Conclusions:
- Hypericin exhibits significant phototoxicity towards Manduca sexta larvae.
- Toxicity is dependent on light exposure, intensity, and wavelength.
- Pre-treatment conditions like starvation can influence the phototoxic potential of hypericin.
