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27 February 2006 Study of photodynamic activity of hypericin and synthetic photosensitizers on haemolysis of erythrocytes in vitro
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Influence of hypericin and synthetic (see manuscript for formula) on haemolysis of human erythrocytes was investigated. It was shown that both hypericin and synthetic porphyrins (TOEPyP and Zn-TOEPyP) did not cause haemolysis in the dark (24 hrs incubation), whereas Ag-TOEPyP leaded to haemolysis already after 40 min incubation, i.e. was cytotoxic. Hypericin (25 μM -125 μM) possessed haemolytic activity upon light exposure (visible spectrum, 30 mW/cm2, 5 min and more). Total haemolysis of erythrocytes was observed at 15 min exposure to light at all the investigated concentrations of hypericin. Dose-dependent haemolytic effect of TOEPyP and Zn-TOEPyP depending on light exposure time was also investigated. TOEPyP demonstrated considerably higher haemolytic activity compared to Zn-TOEPyP. Ag-TOEPyP demonstrated the weakest photodynamic activity. The effect of ascorbic acid on porphyrin-induced haemolysis was also revealed. Ascorbic acid at the concentration of 0.15 μM and above significantly increased haemolysis induced by hypericin, whereas at concentration of 0.75 μM and less it appeared to possess protective property. TOEPyP and Zn-TOEPyP did not demonstrate photodynamic properties in the presence of ascorbic acid (3.75 μM and more). The ascorbic acid at the concentrations below 3.75 μM did not have any influence on erythrocyte haemolysis induced by TOEPyP, while it increased haemolytic effect of Zn-TOEPyP. Thus, the full inhibition of photohaemolysis induced by (see manuscript for formula) by singlet oxygen quenchers - ascorbic acid and tryptophan - was shown. This testifies to the fact, that the photohaemolysis induced by these porphyrins is caused by Type II reactions.
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Hrachik R. Vardapetyan, Susanna G. Tiratsuyan, Ashkhen A. Hovhannisyan, Lernik S. Hunanyan, Alina S. Martirosyan, Robert K. Ghazaryan, Sona S. Ghambaryan, and Grigor V. Gyulkhandanyan "Study of photodynamic activity of hypericin and synthetic photosensitizers on haemolysis of erythrocytes in vitro", Proc. SPIE 6087, Biophotonics and Immune Responses, 608706 (27 February 2006);

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