Many active antioxidants of phenolic structure are present in vegetal biomass as defense mechanism against radiation and infections. Vegetables, cereals, medicinal plants, and algae are traditional sources of these compounds, but the alternative sources are under consideration.
Due to the protective character of phenolic compounds, most of them are distributed in the outer parts of vegetables, which in many cases correspond to agricultural and industrial wastes. Antioxidants are also present in waste liquid effluents from vegetable processing, in a way that if these streams are used as antioxidant sources, a double goal (economic and environmental) can be reached.