Background: 

The superoxide dismutase (SOD) mimetic substances may have therapeutic potential in fighting the neurodegenerative diseases associated with oxidative stress including the spongiform encephalopathies, Alzheimer's and Parkinson's diseases.

The aim of this study was to determine whether Quercetin and Kaempferol (either alone or mixed) are able to modulate the physiological function of manganese superoxide dismutase (MnSOD).

Materials and methods: 

The SOD modulation activity was monitored with a spectrophotometric assay using the xantina/xantina oxidase(XO)-XTT system. The Quercetin and Kaempferol concentrations ranged from 1 to 100 mM for each. When mixed, they were used until the final concentration of 100 mM, ranging from 25mM to 75mM.

Results: 

Quercetinand Kaempferol are activators of SOD or radical scavengers at lower concentrations (<= 50mM) and no significant difference between the two molecules was observed at the lowest concentrations. Instead, they become inhibitors of the enzyme when increasing in concentration. Kaempferol is a stronger inhibitor than Quercetin at 100 mM. The two molecules mixed together show an inhibition activity higher than the Quercetin alone (%RA =-10.0±3.1) and lower than the Kaempferol alone (%RA =-32.6 ± 7.3).

Conclusion: 

these substances act inhibiting the physiological function of the MnSOD at 100mM and increasing the concentration of the superoxide radicals. They act synergically when they are used in mixture.