Positive Health Online

Abstract

Schey and colleagues, Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, USA. investigated the photooxidation properties of hypericin (the active ingredient in St. John's Wort ).

Background

Hypericin is the active ingredient in the over the counter antidepressant medication St. John's Wort. Hypericin produces singlet oxygen and other excited state intermediates that indicate it should be a very efficient phototoxic agent in the eye. It absorbs in the UV and visible range, which means it can potentially damage both the lens and the retina.

Methodology

Lens alpha-crystallin, isolated from calf lenses, was irradiated in the presence of hypericin and in the presence and absence of light. Hypericin-induced photosensitized photopolymerization was assessed by sodium dodecylsulfate-polyacrylamide gel electrophoresis. Further analysis of the oxidative changes occurring in alpha-crystallin using mass spectrometry showed specific oxidation of methionine, tryptophan and histidine residues, which increased with irradiation time. Hypericin did not damage the lens protein in the dark. Damage to alpha-crystallin could undermine the integrity of the lens directly by protein denaturation and indirectly by disturbing chaperone function.

Results

Conclusion

Therefore the authors concluded, in the presence of light, hypericin can induce changes in lens protein that could lead to the formation of cataracts . Appropriate precautions should be taken to protect the eye from intense sunlight while on this antidepressant medication.

References

Schey et al. Photooxidation of lens alpha-crystallin by hypericin (active ingredient in St. John's Wort). Photochemistry and Photobiology 72(2): 200-3. Aug 2000.