This chapter reviews the basic phytochemical characteristics and related biological activity in a range of halophytic species, in addition to their ethnobotanical relevance and traditional use as medicinal plants. The specific features of saline habitats (the osmotic and toxic effects of salts) encourage investigation into halophyte biosynthesis and accumulation of various secondary metabolites produced during adaptation. Recently, therefore, halophytes have become objects of investigation for their qualitative and quantitative characterization and isolation of biologically active substances. Taxonomic and habitat affiliations, main active substances and biological activity have been reviewed and presented for more than 50 halophytic species from families such as: Acanthaceae, Aizoaceae, Amaranthaceae, Apiaceae, Asteraceae, Brassicaceae, Caryophyllaceae, Chenopodiaceae, Combretaceae, Convolvulaceae, Euphorbiaceae, Fabaceae, Frankeniaceae, Fumariaceae, Juncaceae, Lamiaceae, Malvaceae, Plantaginaceae, Plumbaginaceae, Primulaceae, Rhizophoraceae, Salvadoraceae, Saxifragaceae, Tamaricaceae and Zygophyllaceae. Among the most frequent secondary metabolites of halophytes, different types of polyphenols have been determined, including phenolic acids (e.g. chlorogenic acid, vanillic and gallic acids), aromatic acids or phenylpropanoids, flavonoids (such as catechin and isorhamnetin), flavonoid glycosides, isoflavone glycosides, sulfated flavonoids, tannins, stilbenes, curcuminoids and coumarins, in addition to saponins, fatty acids, polyacetylenes, essential oils, carotenoids, alkaloids and other metabolites. We discuss the biological activity of plant extracts and their chemical composition, including, in particular, the antioxidant, antimicrobial and anticancerogenic effects of halophytes.
