This book presents 847 compounds isolated and identified from plants that present antioxidant activity. These substances have been classified by chemical groups and each provides the most relevant information of its pharmacological activity, action mechanism, chemical structure, spectroscopic date and other properties. Chemical structures have been drawn to indicate the stereochemistry. In this handbook the summary of the scientific information of plants that present biological activity and the compounds responsible for this activity is presented, which introduces the reader to the study of medicinal plants and also providing bibliographic references, where a detailed study of its chemistry and pharmacology can be found. This dictionary will be of great help for pre and post-graduate students, as well as professors, research of the medical industry, who work in some way with isolates bioactive compounds obtained from plants.