Biologically active compounds from forage plants

Forage plants have attracted attention for the presence of biologically active compounds that can influence the animal nutrition but may also have a therapeutic potential for humans. These specialized metabolites are in general low-molecular-weight compounds present in low concentration in plants and belong to different chemical classes, including terpenes, saponins, cyanogenic glycosides, flavones, isoflavones, tannins, coumarins and other phenolics. They are involved in various metabolic processes or are stored as inactive precursors which are specifically activated when necessary. The knowledge of bioactive molecules from botanical sources is of great interest for their potential use in pharmaceutical and in the agro-industry. Among forage plants, the Fabaceae (syn. Leguminosae) family is the richest in specialized metabolites. Since forage legumes are widespread and extensively cultivated, they can represent an important source for the extraction of these bioactive phytochemicals. This review deals with bioactive substances from several representative legume forage plants, such as Medicago arabica Huds, M. arborea L., M. polymorpha L., M. sativa L., M. truncatula Gaertn., Trifolium alexandrinum L., T. pratense L., T. repens L., T. subterraneum L., Onobychis viciifolia Scop., Melilotus albus Medik., M. officinalis L. (Pall.), Hedysarum coronarium L., Lotus corniculatus L., L. pedunculatus Cav., Trigonella foenum-graecum L. and Bituminaria bituminosa (L.) C.H. Stirt. Emphasis was given to compounds that usually represent the most active and studied metabolites of the above-mentioned species. Detailed information on their qualitative and quantitative composition were reviewed, as their biological activities are strictly related to their chemical structure and concentration in the plant material. Some information regarding their role in livestock nutrition and their importance for pharmacological application were also reported.