Yeast superoxide dismutase mutants reveal a pro-oxidant action of weak organic acid food preservatives

Saccharomyces cerevisiae could provide a simple experimental system for testing the antioxidant or pro-oxidant actions of chemicals, because it has the capacity for aerobic and anaerobic growth and can readily lose its mitochondrial electron transport chain (the major endogenous source of reactive oxygen species [ROS]). This study showed that yeast superoxide dismutase mutants, in a simple petri dish test, readily distinguish a compound that enhances the detrimental effects of endogenous ROS production by the mitochondrial respiratory chain from another chemical that generates oxidative stress by redox cycling. Using this system, weak organic acid food preservatives are shown to exert a strong pro-oxidant action on aerobic yeast cells. In addition these acids are mutagenic toward the yeast mitochondrial genome, even at levels that are subinhibitory to growth. This raises the concern that the large-scale consumption of these preservatives in the human diet may generate oxidative stress within the epithelia of the gastrointestinal tract. (C) 1999 Elsevier Science Inc.