Plant polyphenol isoflavones

Figure 2 Chemical structures of selected plant polyphenols. Structures include a flavonol (quercetin), isoflavone (daidzein), cinnamic acid (chlorogenic acid), flavan-3-ol (catechin), a lignan microbial metabolite (enterodiol), and a stilbene (resveratrol).

Phytoestrogens are a diverse group of polyphenolic non-steroidal plant compounds that bind to human estrogen receptors (Cos et al., 2003). The best studied of these compounds are the isoflavones, the phytoestrogens present in soy and red clover. 

Plant-derived products Polyphenols (derivatives of hydroxycinnamic acid, hydroxybenzoic acid, flavonols,3 flavones,3 anthocyanidins,3 flavanols,3 isoflavones,3 flavanones,3 stilbenes, lignans), glucosynolates, carotenoids (am /3-, y-, 8-carotene, lycopene, luthein, xeaxantin, canthaxantin), phytic acid, allicin... 

One additional key issue in the field of bacterial enzymatic conversion of polyphenols is enantiospecificity. Many polyphenols, such as isoflavones and lignans, are optically active molecules that display several asymmetric carbon atoms. So far, only S-equol has been detected as a bacterial product of daidzein conversion [95, 120]. In the case of lignans, both (+)- and (-)-enantiomers occur in plants and... 

Flavonoids are a class of plant secondary metabohtes that are abundant components of fruit and vegetables. They are divided into five major subclasses flavonols, flavan-3-ols (monomers and proanthocyanidins), flavones, flavanones and anthocyanins (Manach etal. 2004). Isoflavones are a class of dietary polyphenols present in soya-based foods. The structiues of representative compounds from each of these polyphenol subclasses are shown in Figure 8.2 (also see Chapter 1). Flavonoids and isoflavones have received attention due to their potent antioxidant activity and possible role in the prevention of cancer, cardiovascular, neurodegenerative and infectious diseases as well as osteoporosis. 

Polyphenols are commonly present in fruits, vegetables, nuts, seeds, and flowers. Moreover, polyphenols can be found in such products as cocoa, tea, coffee, wine, jam, and chocolate. Polyphenolic compounds are also often applied in cosmetics, medicines, pharmaceuticals, dietary supplements, and in recent years, for the production of functional foods. The food industry offers a variety of new functional products in which the polyphenol content is usually higher than in products of natural origin. Milk enriched with soy isoflavones, chocolate enriched in procyanidins, drinks with higher amounts of anthocyanins, functional drinks enriched with extracts of tea—these are just a few products that are the result of functional foods revolution. On the other hand, the use of synthetic antioxidants in the food industry is of great concern among consumers who seek to limit their intake. Toxicological and nutritional research indicates adverse effect of some synthetic antioxidants used in food. The use of additives in food products, mainly in edible fats, means that more attention should be paid to antioxidants that are derived from natural plant extracts and used as food additives. 

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