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

The synergic cytotoxic effect of adding ascorbic acid on 5-methoxy-3,4-dehydroxanthomegnin, was investigated. Results indicated that ascorbic acid reduced 5-methoxy-3,4-dehydroxanthomegnin via a semiquinone free radical intermediate, which generate reactive oxygen species. This association resulted in the cytotoxic index being 7 times lower than when 5-methoxy-3,4-dehydroxanthomegnin was added alone to McCoy cell line.