Free radicals, and reactive species (RS) in general, are abundant in living organisms and contribute to a plethora of both beneficial and harmful biological procedures. A shift regarding the biological function of RS has been observed in the field of Redox Biology. Indeed, RS induce oxidative modifications in biomolecules at the subcellular level, thus they are thought to play key roles in the onset of the redox-related ailments¹. Concurrently, they appear to be necessary for normal cellular function promoting redox signalling². The dual action of RS, whose function follows the hermetic theory³ dictates a similar twofold biological role for antioxidants^4,5. Antioxidants become available in humans mainly via their diet. Nutritional antioxidants are referred to polyphenolic compounds mostly, which may exert both protective (i.e., antioxidant) and prooxidant action, thus their advantageous clinical effects are challenged today⁶. Factors such as the dosage (i.e., hermetic effect) of nutritional compounds, the presence of metal ions or the highly reducing environment of cells are key determinants for their Janus-faced action at the cellular and the organismal level.