Identification of the factors responsible for the in vitro pro-oxidant and cytotoxic activities of the olive polyphenols oleuropein and hydroxytyrosol.

The olive polyphenols oleuropein and hydroxytyrosol were reported recently to produce extracellular hydrogen peroxide (H2O2) under standard culture conditions. The precise factors responsible for this production and the conditions promoting or retarding it are critical for the interpretation of the in vitro results. In this study, a systematic evaluation of the components of the most commonly used culture media revealed that sodium bicarbonate is the defining cause for the production of H2O2 by these polyphenols.