Research on the antioxidant properties of edible and medicinal plants is marking sustained growth o decades. A significant number of products obtained from the plant Kingdom like essential oils, alkaloids and polyphenols have antioxidant effects which are evidenced by different in vitro and in vivo assays. However, it is difficult to harmonise and extrapolate the reported results, given the variety of available assays and constraints associated with each of them. The potential of polyphenols as antioxidant agents has been the most popular subject due to its high consumption in the diet and their ubiquitous presence in many plant species. The current state of knowledge shows us that their potential benefits as prophylactic and therapeutic agents are still not fulfil but their applications in the fields of nutraceutics and functional ingredients have been more immediate. In such products, besides their antioxidant capacity, other properties such as the anti-microbial and gastro and cardio-protective activities should be considered. Their use in isolated form is controversial with some authors questioning the real contribution of polyphenols as responsible for the benefits of plants and foods because many polyphenols do not achieve the systemic concentrations required to exert their effects. Therefore, there is an urgent necessity to shed some light about other plant components, a concern which should be shared by the scientific community involved in this area of expertise. Latest evidence points towards a primary action of these compounds in the digestive tract rather than a systemic one, where not only they could display antioxidants properties but that also act as pro-oxidants and/or free radical generators. Thereby, researchers are encouraged to expand the vision currently ascribed to the polyphenolic antioxidants, by proposing new models and experimental protocols, according to the final destination of these compounds.