A COMPARATIVE-STUDY ON THE PHOTOCYTOTOXICITY OF HYPERICIN ON A431 CELLS USING 3 DIFFERENT ASSAYS

Background: Three assay models were adopted for assessing the photocyt otoxicity of hypericin on A431 cells. The cells were incubated for 1 h our of 24 hours with hypericin to evaluate the importance of the incub ation period on the exerted photocytotoxicity. Materials and Methods: A neutral red, an antiproliferative and a tetrazolium-reduction (MTT) assay, were wed for the estimation of cytotoxicity. Results: IC50 valu es were 296, 321 and > 500 nM after 1 hour; and to 70, 54 and 277 nM a fter 24 hours, for the neutral red, antiproliferative and MTT assays, respectively. Conclusions: Our results clearly show that it is imperat ive to incubate cells for long periods to fully assess the hypericin p hotocytotoxicity, and that the neutral red assay is as sensitive as th e antiproliferative assay but superior to the MTT assay at detecting h ypericin cell damage.