Plant secondary metabolites (PSMs) are the intermediate or end products of
the primary metabolism of higher plants and are not involved in metabolic activities.
Primary metabolites are the compounds that are indispensable in the processes of
photosynthesis, respiration, and growth and development. To a certain degree, these
compounds are found in all plants, yet they are common in tropical forages. In spite of
the high cost of energy for the biosynthesis of PSMs, they are produced for protective
purposes. Most halophytic plant species produce secondary metabolites with wide
biological activity, such as tannins, organic acids, carotene, ascorbic acid, glycosides,
absinthin, and essential oils. This chapter discusses the occurrence of PSM's in
halophytes, the origin and divisions of plant secondary metabolites, and the distribution
of PSM's in plant species and organs.
Keywords: Anti-nutritional factors, Carotene, Essential oils, Halophytes, Nitrogen-containing PSM's, Organic acids, PSM's without nitrogen, Secondary metabolites, Tannins.