Opuntia, ficus- indica [L.] Mill. and other species: Source of bioactives and their molecular mechanisms of action to promote human health

Opuntia, a genus of the Cactaceae family, has been used for centuries as a medicinal plant, with different parts of the plant, including whole fruit, pulp, flowers, seeds, peels, and cladodes. Opuntia spp., cultivated or wild, can be found in various agro-climatic conditions, although often associated with warm climate. A dozen species are cultivated for fruit production (O. ficus-indica, O. amyclae, O. xoconostle, O. megacantha, and O. streptacantha), although O. ficus-indica is the most known, as prickly pear fruit, and is available across the five continents from early summer until late autumn. The peculiar general Opuntia anatomy and physiology, and O. ficus-indica specifically, make it a multipurpose dryland crop destined to become more important in view of an ever increasing world population and water and land scarcity. Opuntia fruits contain polyphenols and betalains, promising protective agents against inflammation, oxidative stress, and metabolic-related diseases. Cladodes are not only rich in polyphenols but also contain polysaccharides and soluble fibers that are able to counteract hyperglycemia and related physiological disorders. This chapter reports the latest finding on the health properties of fruit, cladode, flower, and seed from Opuntia plants, related to the bioactive compounds, and the mechanisms of action so far identified or hypothesized. Moreover, the potential uses of Opuntia fruit and cladode are reported, not only for health and disease but also for food applications.