Is Hydrogen Peroxide Generated in Infusions of Medicinal Herbs?

Hydrogen peroxide is an important intra- and inter-cellular messenger. It has been reported that beverages such as tea and coffee generate H2O2. The aim of this study was to examine whether H2O2 is formed in infusions of medicinal herbs and to explain the mechanism of its formation. Infusions of sixteen herbs were studied and the presence of H2O2 was found in all cases. The highest concentrations of H2O2, exceeding 50 mu M, were found in the infusions of leaves of Betula and Polygonum, as well as of the inflorescence of Tilia. Considerable amounts of diverse phenolic compounds were detected in the infusions. Two successive one-electron oxidations of phenolics are the main source of H2O2 in these infusions; as expected, the generation of semiquinone and superoxide radicals was confirmed. The infusions of medicinal herbs were also able to scavenge H2O2. The herbal infusions were cytotoxic to human ovary cancer SKOV-3 and PEO1 cells; this cytotoxicity was compromised by catalase added to the growth medium, demonstrating the contribution of H2O2 to the cytotoxic action of herbal extracts.