Interactions between reactive oxygen species and cancer: the roles of natural dietary antioxidants and their molecular mechanisms of action.

Reactive oxygen species (ROS) are natural products inevitably generated along with cellular metabolism. Due to their extreme reactivity, they can damage DNA, proteins and lipids. Dietary antioxidants have been shown to take part in cellular reduction-oxidation (redox) reactions in which they can act as either antioxidants (election donors) or pro-oxidants (election acceptors) depending on the physiological environment and general oxidative state. Organisms have developed efficient machinery and mechanisms to keep the production of ROS under tight control, these same mechanisms have also been found to regulate other intracellular processes. p53 is a sequence-specific transcription factor and critical tumour suppressor gene that is most frequently mutated in human cancer. Cancer, one of the leading causes of death worldwide, can now be ameliorated, blocked or reversed with ubiquitous polyphenolic and organosulphur compounds present in natural dietary antioxidants.