Background: 

The superoxide dismutase (SOD) is one key antioxidant enzyme implicated in the regulation of reactive oxygen species (ROS) mediated tissue damage. In addition, SOD is likely to play an important role in mediating nitric oxide-induced signalling events. The Quercetin is an important dietary constituent belonging to the flavonols class. It represents the 70% of flavonoids daily intake.

Aim: 

of this work was to study the capacity of Quercetin at different concentrations (1; 10 and 100mM) to modulate the activity of Mn-SOD in order to investigate its role in a variety of oxidant-mediated diseases.

Method: 

the SOD modulation activity was monitored with a spectrophotometric assay using the xantina/xantina oxidase(XO)-XTT system. The assay measures the absorbance variation at 470 nm as a consequence of the Quercetin activity on the SOD.

Results: 

data showed an absorbance decrease of 47,65% at 100mM concentration and a strong increase in absorbance (95,84% and 34,57% respectively) at 1 and 10 mM. In addition Quercetin is able either to react with superoxide radicals directly, or to inhibit XO at the lowest concentration. In fact, in assay without SOD the substance causes a weaker decrease in absorbance (14,06%) at 1 mM.

Conclusion: 

the Quercetin is an activator of SOD at lower concentrations while it becomes inhibitor of the enzyme when increasing its concentration. Therefore, it is able to reduce the concentration of superoxide radicals when it is used at lower concentrations.