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Insecticidal activity of hypericin towardsManduca sexta larvae.

R Samuels1, P Knox

  • 1School of Biological Sciences, University of Bath, BA2 7AY, Claverton Down, Bath Avon, UK.

Journal of Chemical Ecology
|November 26, 2013
PubMed
Summary
This summary is machine-generated.

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.

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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.