3.6. Effect of M. officinalis on epinephrine autoxidation
Here we tested M. officinalis aqueous extract (which presented the highest antioxidant activity in our previous study; Pereira et al., 2009), ethyl acetate fraction (which present the highest antioxidant activity determined in the present study), and two phenolic compounds, gallic acid and quercetin, present in M. officinalis extract as potential inhibitors of epinephrine autoxidation. M. officinalis aqueous extract and ethyl acetate fraction caused a significant inhibition of epinephrine autoxidation only at 1 mg/mL. Gallic acid caused a significant inhibition of epinephrine autoxidation at 100 µM ( Fig. 4C). However, quercetin did not inhibit epinephrine autoxidation ( Fig. 4D). The results indicated that these compounds interact in a different way with superoxide anion, which is involved in autoxidation of epinephrine ( Misra and Fridovich, 1972) and indicated that gallic acid had a modest capacity of scavenge superoxide anion.