Oxidative reactions are vital but also cause important stresses and cellular damages resulting in cancers, cardiovascular or neurodegenerative diseases. Antioxidant secondary metabolites from plant can be mobilized for the cell defense and their main source is precisely the food intake such as vegetables, fruits or beverages. Screening natural active metabolites in plants requires different analytical techniques among which mass spectrometry became one of the most popular, not just because of its ability to provide structural information on involved molecules but also because this technique belongs to the arsenal of diagnostic tool for the determination of biological activities.