Ascorbic acid potentiates the cytotoxicity of the naphthoquinone 5-methoxy-3,4-dehydroxanthomegnin

Abstract

The interaction of ascorbic acid with 5-methoxy-3,4-dehydroxanthomegnin, an 1,4-naphthoquinone, was investigated using the cytotoxic index for McCoy cells by neutral red assay. The synergstic effect was observed when such compounds were added simultaneously, most probably due to hydrogen peroxide being generated by ascorbate - driven 5-methoxy-3,4-dehydroxanthomegnin redox cycling. Incubation of cells in the presence of 5-methoxy-3,4-dehydroxanthomegnin/ascorbic acid/catalase, an enzyme that destroys H(2)O(2), resulted in an increase of cell survival, reinforcing the involvement of hydrogen peroxide generated as an important oxidizing agent that kills McCoy cells. (C) 2008 Elsevier Ltd. All rights reserved.