title: A comparative study on the photocytotoxicity of hypericin on A431 cells using three different assays.
abstract: BACKGROUND
  Three assay models were adopted for assessing the photocytotoxicity of hypericin on A431 cells. The cells were incubated for 1 hour or 24 hours with hypericin to evaluate the importance of the incubation period on the exerted photocytotoxicity.
  
  
  METHODS
  A neutral red, an antiproliferative and a tetrazolium-reduction (MTT) assay were used for the estimation of cytotoxicity.
  
  
  RESULTS
  IC50 values were 296, 321 and > 500 nM after 1 hour, and to 70, 54 and 277 nM after 24 hours, for the neutral red, antiproliferative and MTT assays, respectively.
  
  
  CONCLUSIONS
  Our results clearly show that it is imperative to incubate cells for long periods to fully assess the hypericin photocytotoxicity, and that the neutral red assay is as sensitive as the antiproliferative assay but superior to the MTT assay at detecting hypericin cell damage.
authors.affiliation: Laboratorium voor Farmaceutische Biologie en Fytofarmacologie Faculteit Farmaceutische Wetenschappen, Leuven, Belgium.
authors.forename: F
authors.initials: F
authors.lastname: Ugwu
authors.forename: A L
authors.initials: AL
authors.lastname: Vandenbogaerde
authors.forename: W J
authors.initials: WJ
authors.lastname: Merlevede
authors.forename: P A
authors.initials: PA
authors.lastname: de Witte
mesh_terms: D000873:Anthracenes; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D006801:Humans; D009499:Neutral Red; D010569:Perylene / Q000031:analogs & derivatives* / Q000494:pharmacology; D010778:Photochemotherapy; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D013778:Tetrazolium Salts
chemical_list: D000873:Anthracenes; D000970:Antineoplastic Agents; D011838:Radiation-Sensitizing Agents; D013778:Tetrazolium Salts; D009499:Neutral Red; D010569:Perylene; C004965:hypericin