The effect of Mn(III)-salophen, a superoxide scavenger, against oxidative stress was
evaluated in Escherichia coli sodA- sodB-. Oxidative stress was imposed by exposure of
the cells to paraquat or hyperoxia. Cells were grown in LB medium overnight, washed and
resuspended in the indicated glucose/salts medium supplemented with casamino acids. The
effect of Mn(III)-salophen in the oxidative stress model in vivo was measured in terms of
the cell growth. Mn(III)-salophen ( 60 nM) completely protected E. coliJI132sodA- sodB-against
1.0 μM paraquat. Equivalent amounts of Mn(III) acetate, a Mn(III)-salophen
component, also protected against paraquat toxicity in aerobic E. coli JI132sodA- sodB-.
Fe(III)-salophen which has no superoxide scavenging activity, did not protect the cells against
paraquat toxicity. The protective effect of Mn(III)-salophen against the paraquat toxicity was
proposed to come from the intracellular superoxide scavenging activity of either the complex
itself, its component Mn(III), or both, but not by inhibiting the uptake of paraquat. The
protective effect of Mn(III)-salophen and Mn(III) in the glucose/salts medium containing
casamino acids was also observed in E. coli sodA- sodB- in 100% and 50% oxygen.
Hyperoxia increases intracellular levels of superoxide radicals that are intercepted by Mn(III)salophen
and Mn(III).
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