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Photosensitization of aqueous model systems by hypericin.
V Senthil1, J W Longworth, C A Ghiron
1Physics Department, Illinois Institute of Technology, Chicago 60616.
Biochimica Et Biophysica Acta
|January 23, 1992
Summary
Hypericin (HY) photosensitizes red blood cell membranes and hen lysozyme, demonstrating singlet oxygen involvement in lipid peroxidation and enzyme inactivation. These findings support hypericin
Area of Science:
- Photochemistry
- Biophysics
- Biochemistry
Background:
- Hypericin (HY) is a natural photosensitizer with potential therapeutic applications.
- Understanding HY's interaction with biological systems is crucial for its medicinal use.
Purpose of the Study:
- To investigate the photosensitizing properties of hypericin in aqueous biological systems.
- To elucidate the mechanisms of hypericin-induced damage in red blood cell membranes and hen lysozyme.
Main Methods:
- Absorption and fluorescence spectroscopy were used to characterize hypericin.
- Diffuse reflectance spectroscopy confirmed hypericin solubilization by ghost membranes.
- Photosensitization experiments involved visible light irradiation of hypericin-loaded systems.
- Kinetic analysis and azide ion protection were employed to determine reaction mechanisms.
Main Results:
- Hypericin solubilized in red blood cell membranes induced lipid peroxidation, with evidence of singlet oxygen.
- Hypericin binds strongly to human serum albumin (HSA).
- The hypericin-HSA complex photosensitized hen lysozyme inactivation via a Type II mechanism involving singlet oxygen.
Conclusions:
- Hypericin acts as a photosensitizer in biological membranes and in complex with proteins.
- Singlet oxygen is a key mediator in hypericin-induced photosensitization.
- The findings provide insights into hypericin's photodynamic and potential antiretroviral activities.