Antioxidants in Foods

The concept of antioxidants refers to a substance with the capacity to either directly scavenge or indirectly prevent the formation of pro-oxidant molecules, basically associated to the so called reactive oxygen species (ROS). Considering the cell/tissue target, the picture is quite different. Thus, in animal tissues, the main source for ROS production is the mitochondria, whereas in plants, chloroplast is the most important organelle to generate ROS, including singlet oxygen (O2), superoxide radicals (O2° ̄) or hydrogen peroxide (H2O2). Accordingly, and due to the respective peculiarities, each organelle/cell/tissue has its own antioxidant machinery to overcome the deleterious effects of their internal ROS levels and production.

The real situation is that our cells are continually threatened by ROS, that disturb their normal and pacific living. Oxidative stress arises from an augmented ROS generation, but also from a decay of the antioxidant defense system, leading to the imbalance between the occurrence of reactive species and the organism's ability to counteract them. Oxidative stress is responsible for cell damage, sometimes irrecoverable, which is further implicated in a cascade of degenerative diseases, cardiovascular diseases, cancer and aging. Therefore, in this dangerous situation, the endogenous defense system (which includes antioxidant enzymes and non-enzymatic compounds such as glutathione, vitamins, coenzyme Q and others) needs external help to lower/modulate the negative effects of excessive ROS. This exogenous help is represented by the dietary antioxidants, i.e., food antioxidants, most of them present in fruits and vegetables or other sources from the plant kingdom.