Isoflavones are polyphenolic compounds that are capable of exerting estrogen-like effects. For this reason, they are classified as phytoestrogens—compounds with estrogenic activity derived from plants (1). Legumes, particularly soybeans, are the richest sources of isoflavones in the human diet. In soybeans, isoflavones are present as glycosides (bound to a sugar molecule). Fermentation or digestion of soybeans or soy products results in the release of the sugar molecule from the isoflavone glycoside, leaving an isoflavone aglycone.

Resveratrol (3,4',5-trihydroxystilbene) belongs to a class of polyphenolic compounds called stilbenes (1). Some types of plants produce resveratrol and other stilbenes in response to stress, injury, fungal infection, and ultraviolet (UV) radiation (2). Resveratrol is a fat-soluble compound that occurs in a trans and a cis configuration (see figure 1). Both cis- and trans-resveratrol also occur as glucosides (bound to a glucose molecule). Resveratrol-3-O-beta-glucoside is also called piceid (3).