Phytoestrogens, phytosteroids and saponins in vegetables: Biosynthesis, functions, health effects and practical applications.

Phytoestrogens are non-steroidal secondary metabolites with similarities in structure and biological activities with human estrogens divided into various classes of compounds, including lignans, isoflavones, ellagitannins, coumestans and stilbenes. Similarly, phytosteroids are steroidal compounds of plant origin which have estrogenic effects and can act as agonists, antagonists, or have a mixed agonistic/antagonistic activity to animal steroid receptors. On the other hand, saponins are widely distributed plant glucosides divided into triterpenoid and steroidal saponins that contribute to plant defense mechanism against herbivores. They present a great variation from a structural point of view, including compounds from different classes. In this chapter, the main vegetable sources of these compounds will be presented, while details regarding their biosynthesis and plant functions will be also discussed. Moreover, considering the significant bioactive properties that these compounds exhibit, special focus will be given on their health effects, either beneficial or adverse. The practical applications of these compounds in agriculture and phytomedicine will be also demonstrated, as well as the future prospects for related research.